Ribociclib plus Endocrine Therapy in Early Breast Cancer

BACKGROUND

Ribociclib has been shown to have a significant overall survival benefit in patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer. Whether this benefit in advanced breast cancer extends to early breast cancer is unclear.

METHODS

In this international, open-label, randomized, phase 3 trial, we randomly assigned patients with HR-positive, HER2-negative early breast cancer in a 1:1 ratio to receive ribociclib (at a dose of 400 mg per day for 3 weeks, followed by 1 week off, for 3 years) plus a nonsteroidal aromatase inhibitor (NSAI; letrozole at a dose of 2.5 mg per day or anastrozole at a dose of 1 mg per day for ≥5 years) or an NSAI alone. Premenopausal women and men also received goserelin every 28 days. Eligible patients had anatomical stage II or III breast cancer. Here we report the results of a prespecified interim analysis of invasive disease-free survival, the primary end point; other efficacy and safety results are also reported. Invasive disease-free survival was evaluated with the use of the Kaplan-Meier method. The statistical comparison was made with the use of a stratified log-rank test, with a protocol-specified stopping boundary of a one-sided P-value threshold of 0.0128 for superior efficacy.

RESULTS

As of the data-cutoff date for this prespecified interim analysis (January 11, 2023), a total of 426 patients had had invasive disease, recurrence, or death. A significant invasive disease-free survival benefit was seen with ribociclib plus an NSAI as compared with an NSAI alone. At 3 years, invasive disease-free survival was 90.4% with ribociclib plus an NSAI and 87.1% with an NSAI alone (hazard ratio for invasive disease, recurrence, or death, 0.75; 95% confidence interval, 0.62 to 0.91; P = 0.003). Secondary end points - distant disease-free survival and recurrence-free survival - also favored ribociclib plus an NSAI. The 3-year regimen of ribociclib at a 400-mg starting dose plus an NSAI was not associated with any new safety signals.

CONCLUSIONS

Ribociclib plus an NSAI significantly improved invasive disease-free survival among patients with HR-positive, HER2-negative stage II or III early breast cancer. (Funded by Novartis; NATALEE ClinicalTrials.gov number, NCT03701334.).

Pooled ctDNA analysis of MONALEESA phase III advanced breast cancer trials

BACKGROUND

The phase III MONALEESA trials tested the efficacy and safety of the cyclin-dependent kinase (CDK)4/6 inhibitor ribociclib with different endocrine therapy partners as first- or second-line treatment of hormone receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer (ABC). Using the largest pooled biomarker dataset of the CDK4/6 inhibitor ribociclib in ABC to date, we identified potential biomarkers of response to ribociclib.

PATIENTS AND METHODS

Baseline circulating tumour DNA from patients in the MONALEESA trials was assessed using next-generation sequencing. An analysis of correlation between gene alteration status and progression-free survival (PFS) was carried out to identify potential biomarkers of response to ribociclib.

RESULTS

Multiple frequently altered genes were identified. Alterations in ERBB2, FAT3, FRS2, MDM2, SFRP1, and ZNF217 were associated with a greater PFS benefit with ribociclib versus placebo. Patients with high tumour mutational burden (TMB) and with ANO1, CDKN2A/2B/2C, and RB1 alterations exhibited decreased sensitivity to ribociclib versus placebo.

CONCLUSIONS

Although exploratory, these results provide insight into alterations associated with the improved response to ribociclib treatment and may inform treatment sequencing in patients with actionable alterations following progression on CDK4/6 inhibitors. Validation of potential biomarkers identified here and development of prospective trials testing their clinical utility are warranted.

CLINICALTRIALS

GOV IDENTIFIERS

NCT01958021, NCT02422615, NCT02278120.

Rationale and trial design of NATALEE: a Phase III trial of adjuvant ribociclib + endocrine therapy versus endocrine therapy alone in patients with HR+/HER2- early breast cancer

Background

Ribociclib has demonstrated a statistically significant overall survival benefit in pre- and postmenopausal patients with hormone receptor positive/human epidermal growth factor receptor 2 negative (HR+/HER2-) advanced breast cancer. New Adjuvant Trial with Ribociclib [LEE011] (NATALEE) is a trial evaluating the efficacy and safety of adjuvant ribociclib plus endocrine therapy (ET) versus ET alone in patients with HR+/HER2- early nonmetastatic breast cancer (EBC).

Methods/design

NATALEE is a multicenter, randomized, open-label, Phase III trial in patients with HR+/HER2- EBC. Eligible patients include women, regardless of menopausal status, and men aged ⩾18 years. Select patients with stage IIA, stage IIB, or stage III disease (per the anatomic classification in the AJCC Cancer Staging Manual, 8th edition) with an initial diagnosis ⩽18 months prior to randomization are eligible. Patients receiving standard (neo)adjuvant ET are eligible if treatment was initiated ⩽12 months before randomization. Patients undergo 1:1 randomization to ribociclib 400 mg/day (3 weeks on/1 week off) +ET (letrozole 2.5 mg/day or anastrozole 1 mg/day [investigator's discretion] plus goserelin [men or premenopausal women]) or ET alone. Ribociclib treatment duration is 36 months; ET treatment duration is ⩾60 months. The primary end point is invasive disease-free survival.

Discussion

The 36-month treatment duration of ribociclib in NATALEE is extended compared with that in other adjuvant cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitor trials and is intended to maximize efficacy due to longer duration of CDK4/6 inhibition. Compared with the 600-mg/day dose used in advanced breast cancer, the reduced ribociclib dose used in NATALEE may improve tolerability while maintaining efficacy. NATALEE includes the broadest population of patients with HR+/HER2- EBC of any Phase III trial currently evaluating adjuvant CDK4/6 inhibitor treatment.

Trial registration

ClinicalTrials.gov identifier: NCT03701334 (https://clinicaltrials.gov/ct2/show/NCT03701334).

Abstract P5-02-14: Identification of mechanisms of acquired resistance to ribociclib plus endocrine therapy using baseline and end-of-treatment circulating tumor DNA samples in the MONALEESA-2, -3, and -7 trials

Background: Genetic alterations that contribute to resistance to therapy may be acquired during treatment (tx) for hormone receptor−positive/human epidermal growth factor receptor−negative (HR+/HER2−) advanced breast cancer (ABC). A previous pooled analysis of circulating tumor DNA (ctDNA) in MONALEESA (ML)-2, -3, and -7 identified potential predictive biomarkers for response and resistance to ribociclib (RIB) at baseline (BL). Here, we describe an analysis of paired BL and end of treatment (EOT) samples from ML-2, -3, and -7 to identify acquired mechanisms that may impact resistance to RIB + endocrine therapy (ET) vs placebo (PBO) + ET. Methods: ML-2 (NCT01958021), ML-3 (NCT02422615), and ML-7 (NCT02278120) evaluated efficacy and safety of RIB + ET vs PBO + ET in pre- and postmenopausal patients (pts) with HR+/HER2− ABC treated in first-line (1L) and second-line (2L) settings. Plasma samples were collected at cycle 1 day 1 (C1D1; prior to first therapy exposure) and at EOT (± 28 days of recorded progression). ctDNA was sequenced using a targeted next-generation sequencing panel of ≈550 genes. Genes with an alteration frequency of >5% at EOT, regardless of their frequency at BL, were included. Tumor mutational burden (TMB) was assessed by tx arm; a TMB cutoff of 10 mutations/MB was used to categorize pts as TMB high vs low. To assess differences in the presence of alterations, a McNemar test was performed on paired samples and adjusted (adj) for multiple testing using the false discovery rate (FDR). A Bayesian mixed effects model was used to account for ctDNA fraction and trial and to test for tx-specific resistance by including a tx × visit interaction term. Results: A total of 905 paired samples from ML-2, -3, and -7 were included in this analysis, 441 and 464 samples from pts treated with RIB + ET and PBO + ET, respectively. Overall, 17 genes had an alteration frequency of >5% at EOT. The ctDNA fraction was higher at EOT vs C1D1 in both the RIB (P=.037) and PBO (P=.033) arms. The frequency of alterations in RB1 (10.4% vs 2.0%), ATM (11.3% vs 8.4%), FAT1 (4.8% vs 3.0%), and FAT3 (5.0% vs 2.5%) was higher at EOT vs C1D1 in the RIB arm (FDR-adj P<.10). Alterations in ESR1 were also higher at EOT vs C1D1 in both the RIB (26.3% vs 9.1%) and PBO arms (28.9% vs 5.4%) (FDR-adj P<.0001). Conversely, alterations in GATA3 were higher at EOT in the PBO arm (FDR-adj P=.11). These results were consistent after adjusting for ctDNA fraction. The most common ESR1 mutations were D538G, Y537S/N/C/D, E380Q, and L536H/P/R. Tx × visit interaction effects were observed for RB1 in the RIB arm and GATA3 in the PBO arm, suggesting tx-specific resistance. A tx × visit interaction for ESR1 was also observed, suggesting a larger relative increase in ESR1 mutations with PBO vs RIB. The percentage of pts with high TMB (>10) at EOT increased from 1.1% to 5.7% in the RIB arm and from 1.7% to 3% in the PBO arm. After accounting for ctDNA fraction and trial, a larger numerical increase in TMB was observed for RIB (odds ratio [OR], 9.0; 95% CI, 2.9-32.7) vs PBO (OR, 2.1; 95% CI, 0.7-6.5); however, the model did not support a differential tx effect. Conclusions: This comprehensive analysis of pooled samples from ML-2, -3, and -7 identified acquired gene alterations in pts with HR+/HER2− ABC treated with 1L or 2L RIB + ET or PBO + ET. The frequency of several genes known to contribute to resistance (ESR1, RB1, ATM, FAT1, and FAT3) was higher at EOT vs C1D1 in pts treated with RIB + ET, while ESR1 and GATA3 alterations were higher at EOT vs C1D1 in pts treated with PBO + ET. This paired dataset of BL and EOT samples from pts with HR+/HER2− ABC treated with a CDK4/6 inhibitor and ET is the largest to date and could be used to validate and confirm acquired resistance mechanisms with low alteration frequency.

Citation Format: Fabrice Andre, Nadia Solovieff, Faye Su, Aditya Bardia, Patrick Neven, Yoon-Sim Yap, Debu Tripathy, Yen-Shen Lu, Dennis Slamon, Stephen K. Chia, Mukta Joshi, Arunava Chakravartty, Agnes Lteif, Tetiana Taran, Carlos Arteaga. Identification of mechanisms of acquired resistance to ribociclib plus endocrine therapy using baseline and end-of-treatment circulating tumor DNA samples in the MONALEESA-2, -3, and -7 trials [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-02-14.

Abstract P5-02-32: Differential Gene Mutation Landscape in Patients With PIK3CA-altered and Non-altered Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-negative Advanced Breast Cancer in the SOLAR-1 Clinical Study

Introduction: The phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) is found mutated (mut) in ~40% of patients (pts) with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2−) advanced breast cancer (ABC); some of these alterations can lead to PI3K pathway hyperactivation and are associated with endocrine resistance and poor prognosis in advanced disease. Alpelisib (ALP), an α-selective PI3K inhibitor and degrader, demonstrated clinical benefit in combination with fulvestrant (FUL) in the SOLAR-1 study in pts with PIK3CA-mut HR+, HER2− ABC. SOLAR-1 (NCT02437318) was a double-blind, placebo (PBO)-controlled, stratified, randomized (per PIK3CA-alt status as determined by QIAGEN PIK3CA RGQ PCR test), Phase III study of ALP in combination with FUL in pts with HR+, HER2− ABC who progressed on/after aromatase inhibitor therapy. Here, we compare the gene alteration landscape in pts with altered (alt) and non-alt PIK3CA and the efficacy of ALP + FUL in pts whose tumors have alterations in both selected genes or cell signaling pathways as well as PIK3CA-alt or non-alt status as determined by next-generation sequencing (NGS).

Methods: In this analysis, retrospective NGS analysis using the FoundationOne CDx 324-gene panel was performed on available FFPE tissue samples. In all, 398 pts were categorized into 2 cohorts based on NGS-tested PIK3CA status. The PIK3CA-alt cohort comprised 237 patients (ALP, n=120; PBO, n=117); the PIK3CA-non-alt cohort 161 patients (ALP, n=81; PBO, n=80). Selected genes altered in >20 SOLAR-1 pts were investigated further. Clinical benefit was assessed by progression-free survival (PFS) based on gene alt status in the PIK3CA-alt and -non-alt cohorts. Hazard ratios (HR) for PFS were estimated using a multivariate Cox PH model by adjusting multiple clinical covariates including age, ECOG performance status, bone lesion, prior CDK4/6 inhibitor treatment, and lung/liver metastasis.

Results: PIK3CA-alt and -non-alt cohorts had differential genomic landscapes; differential PFS benefit was observed among the genes analyzed, including ARID1A, EMSY, FGFR2, MAP3K1, MYC, RAD21, RAD51C, TP53, and a gene set associated with the MAPK pathway. In most pts with analyzed gene alterations, numerically longer PFS was observed with ALP vs PBO in the PIK3CA-alt cohort than the -non-alt cohort, particularly pts with alterations in ARID1A (median [m] PFS for ALP vs PBO in PIK3CA-alt cohort: 22.11 vs 12.42 mo, HR 0.48; vs mPFS in PIK3CA-non-alt cohort: 6.21 vs 22.31 mo, HR 1.33) and MAP3K1 (PIK3CA-alt cohort: 17.25 vs 7.70 mo, HR 0.50; vs PIK3CA-non-alt cohort: 9.17 vs 5.26 mo, HR 1.32). Full results are found in the Table. Results should be interpreted with caution, as analyses used small sample sizes and were not adjusted for multiple testing.

Conclusions: A differential genomic landscape was observed in PIK3CA-alt and PIK3CA-non-alt populations. Clinical benefit of ALP vs PBO was observed in pts with PIK3CA-alt disease who also had alterations in analyzed genes and/or genes associated with the MAPK pathway. The data from this analysis suggest that, of the genes analyzed, only PIK3CA mutations can predict pt sensitivity to ALP.

Table. PFS in PIK3CA-altered PIK3CA-non-altered populations by gene alteration

Citation Format: Dejan Juric, Hope Rugo, Albert Reising, Chong Ma, Eva Ciruelos, Sibylle Loibl, Christian F. Singer, Joo Hyuk Sohn, Mario Campone, PierFranco Conte, Hiroji Iwata, Farhat Ghaznawi, Michelle Miller, Tetiana Taran, Faye Su, Fabrice Andre. Differential Gene Mutation Landscape in Patients With PIK3CA-altered and Non-altered Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-negative Advanced Breast Cancer in the SOLAR-1 Clinical Study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-02-32.

Abstract PD17-08: Pooled gene expression analysis and association with treatment response in patients with HR+/HER2− advanced breast cancer in the MONALEESA-2, -3, and -7 trials

Background: The Phase III MONALEESA (ML)-2, -3, and -7 trials showed significant improvement in progression-free survival (PFS) and overall survival (OS) with ribociclib (RIB) + endocrine therapy (ET) over placebo (PBO) + ET in patients (pts) with HR+/HER2− advanced breast cancer (ABC); improvement in OS with cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) has been observed in some, but not all clinical trials. Gene expression analyses for each separate ML study were reported previously. Given the differences in CDK4 vs CDK6 inhibition between RIB and other CDK4/6i, we evaluated the association between cell cycle (CC)–related genes and outcomes based on pooled analysis of gene expression using tumor samples from the ML-2, -3, and -7 trials.

Methods: Gene expression data were generated from pre-treatment archival tumor samples (primary, 73%; metastatic, 27%) with a customized NanoString nCounter panel (781 genes) including genes involved in CC, other signaling pathways, and breast cancer biology. Samples were pooled from 1139 pre- and postmenopausal pts with HR+/HER2− ABC across the 3 ML studies, which included pts on first- and second-line therapy. Data were categorized into training (80%) and test (20%) datasets. The training dataset was used to analyze each gene (modeled continuously) individually for an association with PFS, and genes with a gene × treatment (tx) interaction P value <.10 were evaluated in the test dataset. Genes or gene signatures were classified by tertiles based on expression level (low/medium/high). For each tertile, median (m) PFS was calculated by the Kaplan-Meier method, and hazard ratios (HRs) of tx benefit (RIB vs PBO) were estimated. A Cox proportional hazards model adjusting for clinical covariates was used. A machine learning approach (elastic net survival model with stability selection), which used available gene expression data and select clinical factors and their interactions with tx arms, was applied to predict PFS.

Results: This report focused on CC-related genes and signatures. Gene expression levels of CDKN2B and the expression ratio of CCND1/CDKN2A showed a predictive relationship with benefit from RIB in both training and test sets (Table). PFS benefit with RIB was consistent regardless of the CDK4/CDK6 expression ratio or level of expression of CCNE1, CDK2, RB1, combined CC-related genes, E2F gene signatures, RB gene signature, combined DNA-replication genes, or combined proliferation-related genes. A machine learning approach identified a clinico-genomic signature that was prognostic for PFS benefit with RIB. Selected variables included gene expression levels of FXBO5, PGR, RBBP8, and STC2 and several clinical features (tx arm, de novo disease, prior ET, and visceral disease). Pts with a low signature score had a longer mPFS vs pts with a high signature score, in the RIB (HR, 0.37; 95% CI, 0.22-0.62) and PBO (HR, 0.30; 95% CI, 0.15-0.59) arms.

Conclusion: In the largest pooled analysis of the association of gene expression profile data with CDK4/6i tx response in pts with HR+/HER2− ABC, the PFS benefit with RIB + ET over ET alone was consistent irrespective of expression levels of most CC genes. Variation in magnitude of RIB benefit was observed, depending on CDKN2B expression levels, CCND1/CDKN2A expression ratio, and machine learning–derived signature scores. The clinico-genomic CDK4/6i signature requires validation in additional datasets.

Table 1: Progression-Free Survival by Gene Expression Subgroup

Citation Format: Aditya Bardia, Faye Su, Nadia Solovieff, Fabrice Andre, Carlos Arteaga, Patrick Neven, Yoon-Sim Yap, Yen-Shen Lu, Stephen K. Chia, Dennis Slamon, Seock-Ah Im, Arunava Chakravartty, Agnes Lteif, Tetiana Taran, Debu Tripathy. Pooled gene expression analysis and association with treatment response in patients with HR+/HER2− advanced breast cancer in the MONALEESA-2, -3, and -7 trials [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD17-08.

The study of the cytotoxic effect of disinfectants

The toxicity of individual disinfectants has been studied in vitro using human cell cultures (HT-29 (epithelial-like cells of colon adenocarcinoma), HEK 293 (human embryonic kidney cells)) to create a model for assessing the toxicity of residual amounts of disinfectants that can enter milk for a person. Standard tests have been used to assess cell viability and amount: methyl tetrazolium (MTT) test, neutral red cell staining (NRP), and sulforhodamine B (SRB) test. Disinfectants have a dose- and time-dependent cytotoxic effect on human cell cultures. IC50avg (concentration of the drug that suppresses a certain cell function by 50%) of disinfectants based on the effect on cell cultures (average value) is Biodez – 117.29 ±14 μl/l, Blanidas – 389.25 ±20.83 μl/l, Virkon-S – 343.04 ±28.04 μl/l, Neochlor  – 473.82 ±30.16 μl/l, Phan – 56.71 ±7.05 μl/l, Chlorination – 343.28 ±27.26 μl/l, Chlorinated lime – 117.35 ±9.44 μl/l. Mean toxic doses for cell cultures are lower than the mean lethal dose (based on literature data) for rats and mice by gastric administration. The novelty is that determining the cytotoxicity of disinfectants in vitro using human cell cultures can significantly reduce the number of animals for establishing LD50 during the registration procedure of new agents, making it possible to make preliminary conclusions about the toxicity of substances at the stage of chemical screening, preliminary hygienic regulation, identify target organs of toxic influence.

Alpelisib (ALP) + fulvestrant (FUL) in patients (pts) with hormone receptor–positive (HR+), human epidermal growth factor receptor 2–negative (HER2−) advanced breast cancer (ABC): Biomarker (BM) analyses by next-generation sequencing (NGS) from the SOLAR-1 study

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Background: PIK3CA mutations (mut; ~40% of HR+, HER2– ABC) are linked to poor prognosis. In SOLAR-1, ALP (PI3Kα-selective inhibitor and degrader) + FUL improved progression-free survival (PFS) vs placebo (PBO) + FUL in pts with PIK3CA-mutated HR+, HER2– ABC. Here, we focus on efficacy data by gene alterations in SOLAR-1 PIK3CA-altered (alt) cohort. Methods: SOLAR-1 was a phase 3, randomized, double-blind study of ALP (or PBO) + FUL in HR+, HER2– ABC progressing on/after an aromatase inhibitor. Baseline tissue samples with enough quantity/quality (N = 398) were retrospectively tested by NGS (FoundationOne CDx 324-gene panel) and pts grouped by PIK3CA-alteration status. Clinical benefit was assessed using PFS and hazard ratio (HR) based on tumor mutational burden (TMB) and gene alteration status in the PIK3CA-alt cohort. No multiplicity adjustment was made. Results: PIK3CA-alt (ALP, n = 120; PBO, n = 117) and PI3KCA-non-alt (ALP, n = 81; PBO, n = 80) cohorts had differential gene alteration landscapes. In the PIK3CA-alt cohort, ALP + FUL clinical benefit was seen across TMB quartiles (Q1: 0 -<2.52, Q2: 2.52 -<3.78, Q3: 3.78 -<5.04, Q4: ≥ 5.04 mut/megabase). ALP + FUL had greater benefit in pts with alt vs non-alt FGFR1/ 2 (Table). ALP + FUL benefit was independent of alterations in TP53, ESR1, CCND1, MAP3K1, and ARID1A and limited in MYC- and RAD21-alt cohorts . ALP + FUL benefit was seen in pts with alt genes in the MAPK (HR [95% CI] vs PBO: alt 0.43 [0.23 - 0.80]; non-alt 0.56 [0.40 - 0.79]) and PI3K (in addition to PIK3CA; alt 0.68 [0.38 - 1.23]; non-alt 0.48 [0.34 - 0.68]) pathways, and implicated in CDK4/6i resistance (alt 0.52 [0.30 - 0.89]; non-alt 0.53 [0.37 - 0.76]). Conclusions: The unique mut profile of PIK3CA-alt tumors did not affect ALP + FUL benefit in pts with HR+, HER2– ABC. Clinical benefit was maintained regardless of alterations in most BMs, including ESR1 and genes implicated in CDK4/6i resistance, consistent with ALP targeting the PIK3CA driver oncogene. Clinical trial information: NCT#02437318; EUDRA CT#2015-000340-42. [Table: see text]

Overall Survival with Ribociclib plus Letrozole in Advanced Breast Cancer

BACKGROUND

In a previous analysis of this phase 3 trial, first-line ribociclib plus letrozole resulted in significantly longer progression-free survival than letrozole alone among postmenopausal patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer. Whether overall survival would also be longer with ribociclib was not known.

METHODS

Here we report the results of the protocol-specified final analysis of overall survival, a key secondary end point. Patients were randomly assigned in a 1:1 ratio to receive either ribociclib or placebo in combination with letrozole. Overall survival was assessed with the use of a stratified log-rank test and summarized with the use of Kaplan-Meier methods after 400 deaths had occurred. A hierarchical testing strategy was used for the analysis of progression-free survival and overall survival to ensure the validity of the findings.

RESULTS

After a median follow-up of 6.6 years, 181 deaths had occurred among 334 patients (54.2%) in the ribociclib group and 219 among 334 (65.6%) in the placebo group. Ribociclib plus letrozole showed a significant overall survival benefit as compared with placebo plus letrozole. Median overall survival was 63.9 months (95% confidence interval [CI], 52.4 to 71.0) with ribociclib plus letrozole and 51.4 months (95% CI, 47.2 to 59.7) with placebo plus letrozole (hazard ratio for death, 0.76; 95% CI, 0.63 to 0.93; two-sided P = 0.008). No new safety signals were observed.

CONCLUSIONS

First-line therapy with ribociclib plus letrozole showed a significant overall survival benefit as compared with placebo plus letrozole in patients with HR-positive, HER2-negative advanced breast cancer. Median overall survival was more than 12 months longer with ribociclib than with placebo. (Funded by Novartis; MONALEESA-2 ClinicalTrials.gov number, NCT01958021.).

Abstract GS2-01: Overall survival subgroup analysis by metastatic site from the phase 3 MONALEESA-2 study of first-line ribociclib + letrozole in postmenopausal patients with advanced HR+/HER2− breast cancer

Background: MONALEESA-2 (ML-2) recently reported a statistically significant overall survival (OS) benefit with first-line ribociclib (RIB) + letrozole (LET) over placebo (PBO) + LET in postmenopausal patients with HR+/HER2- advanced breast cancer (ABC) (median, 63.9 vs 51.4 months; hazard ratio, 0.76; 95% CI, 0.63-0.93; P = .004). Understanding OS outcomes in clinically relevant subgroups of patients is important for improving personalized care and prognosis. Here, we report the results of a prespecified exploratory OS analysis in select patient subgroups by baseline location and number of metastatic sites.. Methods: Postmenopausal patients with HR+/HER2− ABC were randomized 1:1 to receive first-line RIB or PBO with LET. Prespecified exploratory OS analyses were performed for subgroups of special interest by baseline location (bone only [yes or no], liver involvement [yes or no], liver or lung involvement [yes or no]) and number of metastatic sites (&lt; 3 or ≥ 3). The data are hypothesis generating since this analysis was exploratory and not powered for statistical significance.. Results: A total of 668 patients were included in the analysis. A consistent improvement in OS was observed with RIB + LET vs PBO + LET in all subgroups regardless of baseline metastatic site (Table). RIB + LET demonstrated an OS benefit over PBO + LET in clinically relevant subgroups by baseline location and number of metastatic sites, including subgroups of patients with liver metastases, liver or lung metastases, and ≥ 3 metastatic sites, who generally have a worse prognosis.. Conclusion: Consistent with the intent-to-treat population of ML-2, the results of this prespecified exploratory analysis demonstrated an OS benefit with RIB + LET independent of the site and number of metastatic lesions.

TableTreatment Arm (n)HR (95% CI)Bone-only metastasisYesRIB + LET (69)0.78 (0.50-1.21)PBO + LET (79)NoRIB + LET (265)0.77(0.61-0.96)PBO + LET (255)Liver involvementYesRIB + LET (59)0.81 (0.54-1.24)PBO + LET (72)NoRIB + LET (275)0.77 (0.62-0.97)PBO + LET (262)Liver or lung involvementYesRIB + LET (182)0.81(0.62-1.05)PBO + LET (190)NoRIB + LET (152)0.71 (0.53-0.96)PBO + LET (144)No. of metastatic sites&lt; 3RIB + LET (220)0.78(0.61-1.00)PBO + LET (222)≥ 3RIB + LET (114)0.71(0.51-0.98)PBO + LET (112)

Citation Format: Joyce O'Shaughnessy, Salomon M Stemmer, Howard A Burris, Yoon-Sim Yap, Gabe Sonke, Lowell Hart, Mario Campone, Katarina Petrakova, Eric P Winer, Wolfgang Janni, Pierfranco Conte, David A Cameron, Fabrice André, Carlos Arteaga, Juan Pablo Zarate, Arunava Chakravartty, Tetiana Taran, Fabienne Le Gac, Paolo Serra, Gabriel N Hortobagyi. Overall survival subgroup analysis by metastatic site from the phase 3 MONALEESA-2 study of first-line ribociclib + letrozole in postmenopausal patients with advanced HR+/HER2− breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr GS2-01.

Abstract GS2-00: Correlative analysis of overall survival by intrinsic subtype across the MONALEESA-2, -3, and -7 studies of ribociclib + endocrine therapy in patients with HR+/HER2− advanced breast cancer

Background: The MONALEESA (ML)-2, -3, and -7 trials have shown a significant benefit in overall survival (OS) with ribociclib (RIB) + endocrine therapy (ET) over placebo (PBO) + ET in HR+/HER2− advanced breast cancer. HR+ breast cancer is a clinically and biologically heterogeneous disease, with identified intrinsic subtypes that vary in incidence, survival rate, and response to treatment. In a pooled analysis of the ML studies, patients with both luminal and HER2-enriched (HER2E) subtypes exhibited a consistent progression-free survival benefit with RIB + ET. The HER2E subtype (RIB, 14%; PBO, 11%), which is associated with ET resistance and poor outcomes, exhibited the greatest relative reduction in risk of progression or death (61%) with RIB + ET. Here, we report a pooled analysis of the ML-2, -3, and -7 trials, presenting OS by intrinsic subtype.. Methods: Tumor samples from patients enrolled in the ML-2, -3, and -7 trials underwent PAM50-based subtyping (blinded from clinical data), and the correlation between intrinsic subtype and OS was analyzed. Gene expression profiling of formalin-fixed, paraffin-embedded tumor samples was performed using a customized NanoString nCounter GX 800-gene panel. The prognostic and/or predictive relationship between PAM50-based subtypes and OS was evaluated using univariable and multivariable Cox proportional hazards models. Multivariable models were adjusted for known clinical prognostic factors, including age, prior chemotherapy, prior ET, ECOG performance status, visceral disease (presence of liver/lung metastases), bone-only metastases, histological grade, number of metastatic sites, tumor type, and de novo metastatic disease.. Results: From the pooled patient population (N = 2066), 997 tumor (71% primary) samples from the RIB (n = 585) and PBO (n = 412) arms of the ML trials (ML-2, n = 318; ML-3, n = 414; ML-7, n = 265) were profiled. Subtype distribution was consistent across treatment arms (Table). A similar benefit with RIB vs PBO was observed in the ITT (hazard ratio [HR], 0.76; 95% CI, 0.67-0.86) and biomarker (HR, 0.75; 95% CI, 0.63-0.89) populations. In both univariable and multivariable analyses, intrinsic subtype was prognostic for OS in both the RIB and PBO arms (P &lt; .0001 for both arms); patients with luminal A subtype had the best OS outcomes in both arms, whereas patients with basal-like subtype had the worst OS outcomes. Intrinsic subtype was also predictive of OS (subtype-treatment interaction: P = .016 [univariable], P = .007 [multivariable]) with a consistent OS benefit with RIB treatment in all subtypes except for basal-like (Table). Patients with HER2E (HR, 0.60; P = .018), luminal B (HR, 0.69; P = .023), and luminal A (HR, 0.75; P = .021) subtypes all derived benefit from RIB. In patients with the basal-like subtype (n = 30), the HR was 1.89 (P = .148); these results should be interpreted with caution due to the small sample size (3% in each arm) and exploratory nature of this analysis.Conclusions: This pooled analysis of the ML trials confirmed the prognostic and predictive value of intrinsic subtype (PAM50 based) for OS. The addition of RIB to ET resulted in consistent OS benefit across all subtypes except for basal-like. The. consistent survival benefit in the HER2E subtype, which is associated with endocrine resistance and a very poor prognosis compared with luminal disease, warrants further investigation.

SubtypeTreatment ArmDistribution, n (%)OS, median (95% CI), monthsHR (95% CI)P ValueaLuminal ARIB320 (55)68.0 (61.5-NR)0.75 (0.58-0.96).021PBO222 (54)54.6 (48.3-66.2)Luminal BRIB154 (26)58.8 (48.3-79.2)0.69 (0.50-0.95).023PBO124 (30)44.9 (35.5-52.6)HER2-enrichedRIB95 (16)40.3 (33.4-49.0)0.60 (0.40-0.92).018PBO52 (13)29.4 (23.9-42.0)Basal-likeRIB16 (3)19.4 (10.7-33.2)1.89 (0.80-4.47).148PBO14 (3)21.2 (12.8-NR)aP values are all two-sided. NR, not reached.

Citation Format: Lisa Carey, Nadia Solovieff, Fabrice André, Joyce O'Shaughnessy, David A Cameron, Wolfgang Janni, Gabe S Sonke, Yoon-Sim Yap, Denise A Yardley, Juan Pablo Zarate, Tetiana Taran, Faye Su, Agnes Lteif, Aleix Prat. Correlative analysis of overall survival by intrinsic subtype across the MONALEESA-2, -3, and -7 studies of ribociclib + endocrine therapy in patients with HR+/HER2− advanced breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr GS2-00.

Abstract PD2-05: Genomic profiling of PAM50-based intrinsic subtypes in HR+/HER2- advanced breast cancer (ABC) across the MONALEESA (ML) studies

Background: In the ML program, PAM50-based intrinsic subtypes (ie, luminal A [LumA], luminal B [LumB], HER2 enriched [HER2E], and basal-like [Basal]) were found to be prognostic and predictive of ribociclib benefit in ABC (Prat et al. J Clin Oncol. 2021). While ribocliclib demonstrated benefit in all subtypes (except Basal, with a limited sample size), LumB and HER2E derived the largest benefit. However, DNA features of the intrinsic subtypes in the advanced setting remain unknown. Here, we report the results of genomic profiling of baseline circulating tumor DNA (ctDNA) by PAM50-based intrinsic subtypes across ML studies. Methods: A total of 883 of 2066 patients recruited in the ML-2, -3, and -7 phase 3 trials had both tumor intrinsic subtype and plasma ctDNA next-generation sequencing (NGS)-based data obtained at baseline (ie, before starting treatment). The NGS-based panel targeted exonic regions in approximately 550 genes sequenced on an Illumina HiSeq instrument. A total of 130 patients had the normal-like subtype and were excluded from further analyses. For genes altered in &gt; 5% of patients, we assessed the differences in frequency across intrinsic subtypes. Genetic alterations included mutations, indels, and copy number alterations. For each gene, a Fisher exact test was used to test for differences in frequency across the subtypes. A false discovery rate (FDR) correction was used to adjust for multiple testing. For genes with FDR &lt; 0.10, a logistic regression model was used to quantify the relationship between subtypes and alteration status. Also, we evaluated differences across subtypes for tumor mutational burden (TMB) using analysis of variance and for ctDNA fraction using a Kruskal-Wallis test. Results: Overall, gene amplifications were more frequent in the LumB, HER2E, and Basal subtypes. CCND1 (and genes FGF3/4/19 found in the same amplicon) was more frequently altered in HER2E (14.6%) and LumB (14.3%) than in the LumA (4.8%) subtype. Similarly, FGFR1 and MYC were more frequently altered in HER2E (13% and 9.8%), Basal (12.5% and 12.5%), and LumB (8.6% and 10%) than in the LumA (3.3% and 2.3%) subtype. PIK3CA alterations, including hotspot somatic mutations, were less frequent in Basal (12.5%) than in the LumB (27.6%), LumA (33.8%), and HER2E (37.4%) subtypes. In contrast, TP53 alterations were more frequent in Basal (66.7%) and HER2E (29.3%) than in the LumB (16.2%) and LumA (12.4%) subtypes. ERBB2 alterations (n = 25) were found in the LumA, LumB, and HER2E subtypes at similar frequencies (3%-4%). ESR1 did not show any significant difference across subtypes. TMB did not differ by subtype (P = .20), even when a TMB cutoff ≥ 10 was used (P = .23). Finally, ctDNA fraction differed across subtypes (P &lt; .001), being significantly higher in the LumB (P &lt; .001) and HER2E (P &lt; .001) than in the LumA subtype. Conclusions: This is the first combined report of ctDNA NGS profiling and intrinsic molecular subtype in ABC. Differences in tumor DNA profiles were observed across PAM50 subtypes, with a trend for higher copy number alterations in HER2E and LumB than in the LumA subtype. LumA and Basal subtypes were found to have the most distinct genomic features. The Basal subtype is known to be similar to triple-negative BC from a clinical and biological perspective, which may explain the limited activity of ribociclib in this subgroup, as shown previously (Prat et al. J Clin Oncol. 2021). The pronounced activity of ribociclib in HER2E and LumB subtypes, which are enriched with somatic alterations associated with endocrine therapy resistance and tend to have a worse prognosis, warrants further investigation.

Citation Format: Aleix Prat, Nadia Solovieff, Faye Su, Aditya Bardia, Patrick Neven, Gabriel N. Hortobagyi, Debu Tripathy, Stephen Chia, Dennis Slamon, Yen-Shen Lu, Tetiana Taran, Agnes Lteif, Carlos L. Arteaga, Fabrice André. Genomic profiling of PAM50-based intrinsic subtypes in HR+/HER2- advanced breast cancer (ABC) across the MONALEESA (ML) studies [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD2-05.

Genomic Profiling of Premenopausal HR+ and HER2- Metastatic Breast Cancer by Circulating Tumor DNA and Association of Genetic Alterations With Therapeutic Response to Endocrine Therapy and Ribociclib

PURPOSE

This analysis evaluated the genomic landscape of premenopausal patients with hormone receptor–positive and human epidermal growth factor receptor 2–negative advanced breast cancer and the association of genetic alterations with response to ribociclib in the phase III MONALEESA-7 trial.

METHODS

Premenopausal patients were randomly assigned 1:1 to receive endocrine therapy plus ribociclib or placebo. Plasma collected at baseline was sequenced using targeted next-generation sequencing for approximately 600 relevant cancer genes. The association of circulating tumor DNA alterations with progression-free survival (PFS) was evaluated to identify biomarkers of response and resistance to ribociclib.

RESULTS

Baseline circulating tumor DNA was sequenced in 565 patients; 489 had evidence of ≥ 1 alteration. The most frequent alterations included PIK3CA (28%), TP53 (19%), CCND1 (10%), MYC (8%), GATA3 (8%), receptor tyrosine kinases (17%), and the Chr8p11.23 locus (12%). A treatment benefit of ribociclib was seen with wild-type (hazard ratio [HR] 0.45 [95% CI, 0.33 to 0.62]) and altered (HR 0.57 [95% CI, 0.36 to 0.9]) PIK3CA. Overall, patients with altered CCND1 had shorter PFS regardless of treatment, suggesting CCND1 as a potential prognostic biomarker. Benefit with ribociclib was seen in patients with altered (HR 0.21 [95% CI, 0.08 to 0.54]) or wild-type (HR 0.52 [95% CI, 0.39 to 0.68]) CCND1, but greater benefit was observed with altered, suggesting predictive potential of CCND1. Alterations in TP53, MYC, Chr8p11.23 locus, and receptor tyrosine kinases were associated with worse PFS, but ribociclib benefit was independent of alteration status.

CONCLUSION

In this study—to our knowledge, the first large study of premenopausal patients with hormone receptor–positive and human epidermal growth factor receptor 2–negative advanced breast cancer—multiple genomic alterations were associated with poor outcome. A PFS benefit of ribociclib was observed regardless of gene alteration status, although in this exploratory analysis, a magnitude of benefits varied by alteration.

Ribociclib plus fulvestrant for postmenopausal women with hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer in the phase III randomized MONALEESA-3 trial: updated overall survival

BACKGROUND

Ribociclib plus fulvestrant demonstrated significant progression-free survival (PFS) and overall survival (OS) benefits in patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced breast cancer (ABC). Here we present a new landmark in survival follow-up for a phase III cyclin-dependent kinases 4 and 6 inhibitor clinical trial in patients with ABC (median, 56.3 months).

PATIENTS AND METHODS

This phase III, randomized, double-blind, placebo-controlled trial was conducted at 174 sites (30 countries). Patients were men and postmenopausal women (age ≥18 years) with histologically/cytologically confirmed HR+/HER2- ABC. Patients could have received ≤1 line of endocrine therapy (ET) but no chemotherapy for ABC. Patients, assigned 2:1, were stratified by the presence/absence of liver/lung metastases and previous ET. Patients received intramuscular fulvestrant (500 mg, day 1 of each 28-day cycle plus day 15 of cycle 1) with oral ribociclib (600 mg/day, 3 weeks on, 1 week off) or placebo. Efficacy analyses were by intention to treat. Safety was assessed in patients receiving ≥1 dose study treatment. OS was a secondary endpoint. MONALEESA-3 is registered with ClinicalTrials.gov (NCT02422615; no longer enrolling).

RESULTS

Between 18 June 2015 and 10 June 2016, 726 patients were randomly assigned (484, ribociclib; 242, placebo). At data cut-off (30 October 2020), median OS (mOS) was 53.7 months (ribociclib) versus 41.5 months (placebo) [hazard ratio (HR), 0.73; 95% confidence interval (CI) 0.59-0.90]. Subgroup analyses were consistent with overall population. In the first-line setting, most patients in the ribociclib arm (∼60%) lived longer than median follow-up; mOS was 51.8 months in the placebo arm (HR, 0.64; 95% CI 0.46-0.88). In the second-line setting, mOS was 39.7 months (ribociclib) versus 33.7 months (placebo) (HR, 0.78; 95% CI 0.59-1.04). No apparent drug-drug interaction between ribociclib and fulvestrant or new safety signals were observed.

CONCLUSIONS

This analysis reported extended OS follow-up in MONALEESA-3. mOS was ∼12 months longer in patients with HR+/HER2- ABC treated with ribociclib plus fulvestrant compared with fulvestrant monotherapy.

Updated overall survival (OS) results from the phase III MONALEESA-3 trial of postmenopausal patients (pts) with HR+/HER2- advanced breast cancer (ABC) treated with fulvestrant (FUL) ± ribociclib (RIB)

1001

Background: The Phase III MONALEESA-3 trial (NCT02422615) previously demonstrated a statistically significant improvement in OS with RIB, a cyclin-dependent kinase 4/6 inhibitor (CDK4/6i), plus FUL compared with placebo (PBO) plus FUL as first-line (1L) or second-line (2L) treatment in postmenopausal pts with HR+/HER2− ABC (median, not reached vs 40.0 mo; hazard ratio [HR], 0.72; 95% CI, 0.57-0.92, P =.00455). This analysis was final per the protocol; following the unblinding of the study, pts still on study treatment in the PBO arm were allowed to cross over to the RIB arm. We report an exploratory analysis of OS after an additional median 16.9 mo of follow-up, allowing for further characterization of long-term survival benefits of RIB. Methods: Postmenopausal pts with HR+/HER2− ABC were randomized 2:1 to receive RIB + FUL or PBO + FUL in 1L and 2L settings. Updated OS was evaluated by Cox proportional hazards model and summarized using Kaplan-Meier methods. Additional postprogression endpoints such as progression-free survival 2 (PFS2), time to chemotherapy (CT), and CT-free survival were also evaluated and summarized. Results: At the data cutoff (Oct 30, 2020), the median follow-up was 56.3 mo (min, 52.7 mo) and 68 (14.0%) and 21 (8.7%) patients were still on treatment in the RIB vs PBO arms, respectively. With this extended follow-up, RIB + FUL continued to demonstrate an OS benefit vs PBO + FUL (median, 53.7 vs 41.5 mo; HR, 0.73; 95% CI, 0.59-0.90). RIB + FUL had prolonged OS vs PBO + FUL in the 1L (median, not reached vs 51.8 mo; HR, 0.64; 95% CI, 0.46-0.88) and 2L subgroups (median, 39.7 vs 33.7 mo; HR, 0.78; 95% CI, 0.59-1.04). Subgroup analyses also showed a consistent OS benefit compared with the intent-to-treat (ITT) population for most subgroups. PFS2, time to CT, and CT-free survival for the ITT population favored RIB + FUL (Table). Among pts who discontinued study treatment, 81.9% and 86.4% received a next-line subsequent antineoplastic therapy, while 14.0% and 30.0% received a CDK4/6i as any subsequent line in the RIB vs PBO arms, respectively. No new safety signals were observed. Conclusions: The previously demonstrated robust and clinically meaningful OS benefit with RIB + FUL compared with PBO + FUL was maintained after almost 5 years of follow-up in postmenopausal pts with HR+/HER2− ABC. The OS benefit of RIB was observed in the 1L and 2L subgroups, which further supports the use of RIB in these populations. The results also demonstrated a significant delay in the use of subsequent CT with RIB vs PBO. Clinical trial information: NCT02422615 .[Table: see text]

Correlative Biomarker Analysis of Intrinsic Subtypes and Efficacy Across the MONALEESA Phase III Studies

PURPOSE

The prognostic and predictive value of intrinsic subtypes in hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer treated with endocrine therapy and ribociclib (RIB) is currently unknown. We evaluated the association of intrinsic subtypes with progression-free survival (PFS) in the MONALEESA trials.

METHODS

A retrospective and exploratory PAM50-based analysis of tumor samples from the phase III MONALEESA-2, MONALEESA-3, and MONALEESA-7 trials was undertaken. The prognostic relationship of PAM50-based subtypes with PFS and risk of disease progression by subtype and treatment were evaluated using a multivariable Cox proportional hazards model, adjusting for age, prior chemotherapy, performance status, visceral disease, bone-only metastases, histological grade, number of metastatic sites, prior endocrine therapy, and de novo metastatic disease.

RESULTS

Overall, 1,160 tumors from the RIB (n = 672) and placebo (n = 488) cohorts were robustly profiled. Subtype distribution was luminal A (LumA), 46.7%; luminal B (LumB), 24.0%; normal-like, 14.0%; HER2-enriched (HER2E), 12.7%; and basal-like, 2.6% and was generally consistent across treatment arms and trials. The associations between subtypes and PFS were statistically significant in both arms (P < .001). The risks of disease progression for LumB, HER2E, and basal-like subtypes were 1.44, 2.31, and 3.96 times higher compared with those for LumA, respectively. All subtypes except basal-like demonstrated significant PFS benefit with RIB. HER2E (hazard ratio [HR], 0.39; P < .0001), LumB (HR, 0.52; P < .0001), LumA (HR, 0.63; P = .0007), and normal-like (HR, 0.47; P = .0005) subtypes derived benefit from RIB. Patients with basal-like subtype (n = 30) did not derive benefit from RIB (HR, 1.15; P = .77).

CONCLUSION

In this retrospective exploratory analysis of hormone receptor-positive and human epidermal growth factor receptor 2-negative advanced breast cancer, each intrinsic subtype exhibited a consistent PFS benefit with RIB, except for basal-like.

Abstract GS1-04: Correlative biomarker analysis of intrinsic subtypes and efficacy across the MONALEESA Phase III studies

Background: The prognostic and predictive value of the 4 main intrinsic subtypes of breast cancer (ie, luminal A [LumA], luminal B [LumB], human epidermal growth factor receptor 2 enriched [HER2E], and basal-like) in hormone receptor-positive, HER2− advanced breast cancer (ABC) treated with endocrine therapy (ET) and ribociclib (RIB) is currently unknown. The MONALEESA-2, -3, and -7 trials all showed a significant benefit in progression-free survival (PFS) with RIB over placebo (PBO; Hortobagyi et al. Ann Oncol. 2018; Slamon et al. J Clin Oncol. 2018; Tripathy et al. Lancet Oncol. 2018). Here, we correlate ABC intrinsic subtypes with the PFS benefit of RIB in the MONALEESA trials. Methods: Patient samples from the MONALEESA-2, -3, and -7 trials underwent PAM50-based subtyping (blinded from clinical data), and the correlation between intrinsic subtype and PFS was analyzed. Gene expression profiling of formalin-fixed, paraffin-embedded tumor samples was performed using a customized NanoString nCounter GX 800-gene panel. The prognostic and/or predictive relationship of PAM50-based subtypes with PFS and the risk of tumor progression by subtype were evaluated using univariate and multivariable Cox proportional hazards models. Multivariable models were adjusted for known clinical prognostic factors, including age, prior chemotherapy, prior ET, ECOG performance status, visceral disease (presence of liver/lung metastases), bone-only metastases, histological grade, number of metastatic sites, and de novo metastatic disease. Results: A total of 1160 tumor samples from both the RIB (n = 672) and PBO (n = 488) treatment arms of the MONALEESA trials were profiled. Subtype distribution was generally consistent across treatment arms (Table). The associations between intrinsic subtypes and PFS were statistically significant in both treatment arms (P &lt; .0001). Compared with patients with LumA subtype, which is the subtype that is the most prevalent and has the best prognostic outcome, patients with LumB, HER2E, and basal-like subtypes had a 1.41, 2.30, and 3.97 times higher risk of tumor progression, respectively, after adjusting for other clinical-pathologic variables and treatment arm. In terms of treatment benefit, all subtypes except for basal-like showed a significant PFS benefit with RIB treatment (Table). Patients with HER2E (hazard ratio [HR], 0.389; P &lt; .0001), LumB (HR, 0.521; P = .0001), LumA (HR, 0.633; P = .0007), and normal-like (HR, 0.467; P = .0005) subtypes all derived benefit from RIB treatment, with HER2E demonstrating the greatest benefit. Patients with the basal-like subtype (n = 30) did not derive benefit from RIB (HR, 1.15; P = .767), although these results should be interpreted with caution due to the small sample size (RIB: 2%; PBO: 3%). Conclusions: This is the largest analysis evaluating the correlation of intrinsic ABC subtype with efficacy outcomes in patients treated with CDK4/6 inhibitors. Patients with HER2E, LumA, LumB, and normal-like subtypes all exhibited a consistent PFS benefit with RIB treatment, while patients with basal-like ABC (RIB: 2%; PBO: 3%) did not. The HER2E subtype (RIB: 14%; PBO: 11%) exhibited the greatest relative reduction in risk of progression or death (61%) with RIB plus ET.

Table.SubtypeTreatment ArmDistribution, n (%)Median PFS, months, (95% CI)HRP ValueLuminal ARIB320 (48)29.60 (23.03-NA)0.63.0007PBO222 (45)19.48 (15.61-24.80)Luminal BRIB154 (23)22.21 (18.79-NA)0.52&lt; .0001PBO124 (25)12.85 (10.98414.82)HER2-enrichedRIB95 (14)16.39 (12.71-24.6)0.39&lt; .0001PBO52 (11)5.52 (3.12-9.17)BasalRIB16 (2)3.71 (1.91-13)1.15.77PBO14 (3)3.58 (1.87-NA)NormalRIB87 (13)22.34 (16.56-NA)0.47.0005PBO76 (16)11.10 (7.39-16.56)NA, not achieved.

Citation Format: Aleix Prat, Anwesha Chaudhury, Nadia Solovieff, Laia Paré, Debora Martinez, Nuria Chic, Olga Martínez, Fara Brasó-Maristany, Karen Rodriguez-Lorenc, Tetiana Taran, Naveen Babbar, Faye Su. Correlative biomarker analysis of intrinsic subtypes and efficacy across the MONALEESA Phase III studies [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr GS1-04.

Pooled ctDNA analysis of the MONALEESA (ML) phase III advanced breast cancer (ABC) trials

1009

Background: Biomarker analyses have been presented separately for each Phase III ML trial, which tested efficacy and safety of ribociclib (RIB) with different endocrine therapy (ET) combination partners as first- or second-line treatment for hormone receptor–positive, HER2-negative (HR+/HER2−) ABC. Here, using the largest pooled biomarker dataset of a CDK4/6 inhibitor in ABC to date, we identify potential biomarkers of response or resistance to RIB across ML trials. Methods: Baseline ctDNA from 1503 patients (pts) enrolled in ML-2, 3, and 7 was assessed using next-generation sequencing with a targeted panel of 557 genes. Genes with an alteration frequency ≥2% and in ≥15 pts per treatment arm were included (83 genes). Genetic alteration was defined as presence of a mutation, short insertion/deletion, or copy number alteration. Cox proportional hazard model of progression-free survival (PFS) was fit with gene-by-treatment interaction. Genes with interaction P< 0.10 and genes of interest were investigated. Results: Pts with alterations in FRS2 and PRKCA (treatment interaction P< 0.05) as well as MDM2, ERBB2, AKT1, and BRCA1/2 ( P> 0.05 but considered actionable) had a trend for increased PFS benefit of RIB vs PBO (Table). Pts with alterations in CHD4, BCL11B, ATM, or CDKN2A/2B/2C derived little to no added PFS benefit with RIB vs PBO ( P interaction < 0.10; hazard ratio [HR] > 0.80). Data on genes implicated in the literature as potential mechanisms of resistance to ET and/or CDK4/6 inhibition ( ESR1, PTEN, FAT1, RB1, and NF1) will be presented. Conclusions: Results of this pooled analysis of the ML-2, 3, and 7 trials, the largest biomarker analysis of any CDK4/6 inhibitor in ABC, revealed several potential biomarkers of response ( FRS2, MDM2, PRKCA, ERBB2, AKT1, and BRCA1/2) or resistance ( CHD4, BCL11B, ATM, or CDKN2A/2B/2C) to RIB. Clinical trial information: NCT01958021; NCT02422615; NCT02278120 . [Table: see text]

Overall Survival with Ribociclib plus Fulvestrant in Advanced Breast Cancer

BACKGROUND

In an earlier analysis of this phase 3 trial, ribociclib plus fulvestrant showed a greater benefit with regard to progression-free survival than fulvestrant alone in postmenopausal patients with hormone-receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer. Here we report the results of a protocol-specified second interim analysis of overall survival.

METHODS

Patients were randomly assigned in a 2:1 ratio to receive either ribociclib or placebo in addition to fulvestrant as first-line or second-line treatment. Survival was evaluated by means of a stratified log-rank test and summarized with the use of Kaplan-Meier methods.

RESULTS

This analysis was based on 275 deaths: 167 among 484 patients (34.5%) receiving ribociclib and 108 among 242 (44.6%) receiving placebo. Ribociclib plus fulvestrant showed a significant overall survival benefit over placebo plus fulvestrant. The estimated overall survival at 42 months was 57.8% (95% confidence interval [CI], 52.0 to 63.2) in the ribociclib group and 45.9% (95% CI, 36.9 to 54.5) in the placebo group, for a 28% difference in the relative risk of death (hazard ratio, 0.72; 95% CI, 0.57 to 0.92; P = 0.00455). The benefit was consistent across most subgroups. In a descriptive update, median progression-free survival among patients receiving first-line treatment was 33.6 months (95% CI, 27.1 to 41.3) in the ribociclib group and 19.2 months (95% CI, 14.9 to 23.6) in the placebo group. No new safety signals were observed.

CONCLUSIONS

Ribociclib plus fulvestrant showed a significant overall survival benefit over placebo plus fulvestrant in patients with hormone-receptor-positive, HER2-negative advanced breast cancer. (Funded by Novartis; MONALEESA-3 ClinicalTrials.gov number, NCT02422615.).

Abstract A031: Association of tumor DNA in circulation with clinical characteristics and treatment response in HR+/HER2− advanced breast cancer

Background: The sensitivity of plasma-based oncological assays is influenced by the amount of tumor DNA shed into the circulation (ctDNA fraction). Higher ctDNA fraction has been shown to correlate with later-stage cancers and poorer overall survival (Bettegowda C, et al. Sci Transl Med. 2014; Dawson SJ, et al. N Engl J Med. 2014). Other factors affecting ctDNA fraction are poorly understood. We present results from three large Phase III breast cancer studies (MONALEESA-2, -3, and -7) to evaluate correlations between ctDNA fraction and clinical characteristics and impact on progression-free survival (PFS) and best overall tumor response. Methods: Baseline plasma samples were collected from patients (pts) in the MONALEESA-2, -3, and -7 studies, which are Phase III registration trials testing ribociclib, a cyclin-dependent kinase 4/6 inhibitor, in hormone receptor–positive, human epidermal growth factor receptor 2–negative advanced breast cancer. For each trial, cell-free DNA was extracted from plasma and sequenced using a validated next-generation sequencing assay targeting approximately 550 genes. ctDNA fraction was estimated by analyzing short-read sequences using PureCN (Riester M, et al. Source Code Biol Med. 2016) and tested for correlations with various tumor characteristics (size at baseline, Ki67 expression, number and type of metastatic sites, hormone receptor status) and pt characteristics (type of prior therapy, line of therapy, ECOG performance status, age, body mass index, race, histological grade, menopausal status). We also evaluated the prognostic value of ctDNA fraction on PFS and best overall response. To evaluate the prognostic effect on PFS, ctDNA fraction was binned into 3 categories (not detectable; low, 0.5%-10%; high, &gt; 10%). Results: Higher ctDNA fractions were observed in pts with more metastatic sites (P &lt; 0.0001), larger tumor diameter (P &lt; 0.0001), higher Ki67 expression (P = 0.0001), higher lactate dehydrogenase levels (P &lt; 0.0001), higher-grade tumors (P = 0.0004), worse ECOG performance status (P &lt; 0.0001), progesterone receptor–negative tumors (P = 0.01), presence of liver metastases (P &lt; 0.0001), and shorter disease-free intervals (P &lt; 0.0001). ctDNA fractions were also higher in younger pts (continuous variable; P &lt; 0.0001) and pts with lower BMI (P = 0.0003), prior chemotherapy (P = 0.002), and prior endocrine therapy (P = 0.01). Lower ctDNA fractions were observed in pts with better overall response (P &lt; 0.0001), with median ctDNA fractions lowest in pts with complete responses followed by partial response, stable disease, and progressive disease. Pts with low (0.5%-10%) ctDNA fractions had longer PFS than pts with high (&gt; 10%) ctDNA fractions (HR [95% CI], 0.63 [0.48-0.82], 0.64 [0.51-0.80], and 0.67 [0.52-0.86] in the MONALEESA-2, -3, and -7 trials, respectively). A more pronounced effect on PFS was observed in pts with undetectable levels of ctDNA vs pts with higher ctDNA fractions (HR [95% CI], 0.35 [0.23-0.52], 0.34 [0.21-0.55], and 0.31 [0.21-0.47] in the MONALEESA-2, -3, and -7 trials, respectively). Conclusions: Generally, higher ctDNA fraction was associated with more aggressive tumor characteristics and prior exposure to therapy. Lower ctDNA fraction was associated with longer PFS and better overall response. Together these data suggest that ctDNA fraction is a robust prognostic factor.

Citation Format: Nadia Solovieff, Faye Su, Rebecca Leary, Alejandro Balbin, Arunava Chakravartty, Karen Rodriguez Lorenc, Tetiana Taran, Naveen Babbar. Association of tumor DNA in circulation with clinical characteristics and treatment response in HR+/HER2− advanced breast cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr A031. doi:10.1158/1535-7163.TARG-19-A031

Everolimus Plus Exemestane vs Everolimus or Capecitabine Monotherapy for Estrogen Receptor-Positive, HER2-Negative Advanced Breast Cancer: The BOLERO-6 Randomized Clinical Trial

Importance

Everolimus plus exemestane and capecitabine are approved second-line therapies for advanced breast cancer.

Objective

A postapproval commitment to health authorities to estimate the clinical benefit of everolimus plus exemestane vs everolimus or capecitabine monotherapy for estrogen receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer.

Design

Open-label, randomized, phase 2 trial of treatment effects in postmenopausal women with advanced breast cancer that had progressed during treatment with nonsteroidal aromatase inhibitors.

Interventions

Patients were randomized to 3 treatment regimens: (1) everolimus (10 mg/d) plus exemestane (25 mg/d); (2) everolimus alone (10 mg/d); and (3) capecitabine alone (1250 mg/m2 twice daily).

Main Outcomes and Measures

Estimated hazard ratios (HRs) of progression-free survival (PFS) for everolimus plus exemestane vs everolimus alone (primary objective) or capecitabine alone (key secondary objective). Safety was a secondary objective. No formal statistical comparisons were planned.

Results

A total of 309 postmenopausal women were enrolled, median age, 61 years (range, 32-88 years). Of these, 104 received everolimus plus exemestane; 103, everolimus alone; and 102, capecitabine alone. Median follow-up from randomization to the analysis cutoff (June 1, 2017) was 37.6 months. Estimated HR of PFS was 0.74 (90% CI, 0.57-0.97) for the primary objective of everolimus plus exemestane vs everolimus alone and 1.26 (90% CI, 0.96-1.66) for everolimus plus exemestane vs capecitabine alone. Between treatment arms, potential informative censoring was noted, and a stratified multivariate Cox regression model was used to account for imbalances in baseline characteristics; a consistent HR was observed for everolimus plus exemestane vs everolimus (0.73; 90% CI, 0.56-0.97), but the HR was closer to 1 for everolimus plus exemestane vs capecitabine (1.15; 90% CI, 0.86-1.52). Grade 3 to 4 adverse events were more frequent with capecitabine (74%; n = 75) vs everolimus plus exemestane (70%; n = 73) or everolimus alone (59%; n = 61). Serious adverse events were more frequent with everolimus plus exemestane (36%; n = 37) vs everolimus alone (29%; n = 30) or capecitabine (29%; n = 30).

Conclusions and Relevance

These findings suggest that everolimus plus exemestane combination therapy offers a PFS benefit vs everolimus alone, and they support continued use of this therapy in this setting. A numerical PFS difference with capecitabine vs everolimus plus exemestane should be interpreted cautiously owing to imbalances among baseline characteristics and potential informative censoring.

Trial Registration

ClinicalTrials.gov identifier: NCT01783444.

Overall Survival with Ribociclib plus Endocrine Therapy in Breast Cancer

BACKGROUND

An earlier analysis of this phase 3 trial showed that the addition of a cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor to endocrine therapy provided a greater benefit with regard to progression-free survival than endocrine therapy alone in premenopausal or perimenopausal patients with advanced hormone-receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer. Here we report the results of a protocol-specified interim analysis of the key secondary end point of overall survival.

METHODS

We randomly assigned patients to receive either ribociclib or placebo in addition to endocrine therapy (goserelin and either a nonsteroidal aromatase inhibitor or tamoxifen). Overall survival was evaluated with the use of a stratified log-rank test and summarized with the use of Kaplan-Meier methods.

RESULTS

A total of 672 patients were included in the intention-to-treat population. There were 83 deaths among 335 patients (24.8%) in the ribociclib group and 109 deaths among 337 patients (32.3%) in the placebo group. The addition of ribociclib to endocrine therapy resulted in significantly longer overall survival than endocrine therapy alone. The estimated overall survival at 42 months was 70.2% (95% confidence interval [CI], 63.5 to 76.0) in the ribociclib group and 46.0% (95% CI, 32.0 to 58.9) in the placebo group (hazard ratio for death, 0.71; 95% CI, 0.54 to 0.95; P = 0.00973 by log-rank test). The survival benefit seen in the subgroup of 495 patients who received an aromatase inhibitor was consistent with that in the overall intention-to-treat population (hazard ratio for death, 0.70; 95% CI, 0.50 to 0.98). The percentage of patients who received subsequent antineoplastic therapy was balanced between the groups (68.9% in the ribociclib group and 73.2% in the placebo group). The time from randomization to disease progression during receipt of second-line therapy or to death was also longer in the ribociclib group than in the placebo group (hazard ratio for disease progression or death, 0.69; 95% CI, 0.55 to 0.87).

CONCLUSIONS

This trial showed significantly longer overall survival with a CDK4/6 inhibitor plus endocrine therapy than with endocrine therapy alone among patients with advanced hormone-receptor-positive, HER2-negative breast cancer. No new concerns regarding toxic effects emerged with longer follow-up. (Funded by Novartis; MONALEESA-7 ClinicalTrials.gov number, NCT02278120.).

Abstract CT141: Genetic landscape of premenopausal HR+/HER2- advanced breast cancer (ABC) based on comprehensive circulating tumor DNA analysis and association with clinical outcomes in the Phase III MONALEESA-7 trial

Background: The genetic landscape of premenopausal hormone receptor-positive (HR+) ABC is not well understood. The Phase III MONALEESA-7 study (NCT02278120), the first trial of endocrine therapy ± a cyclin-dependent kinase 4/6 inhibitor for premenopausal patients (pts) with HR+/human epidermal growth factor receptor 2-negative (HER2-) ABC, demonstrated that the addition of ribociclib (RIB) to a nonsteroidal aromatase inhibitor (NSAI) or tamoxifen (TAM) + goserelin (GOS) significantly extended progression-free survival (PFS; Tripathy D, et al. Lancet Oncol. 2018). We conducted a comprehensive ctDNA genomic analysis from MONALEESA-7.

Methods: Premenopausal pts with HR+/HER2- ABC were randomized 1:1 to RIB or placebo (PBO) + NSAI (letrozole [LET] or anastrozole) or TAM + GOS. Plasma samples for ctDNA analysis were collected at baseline and end of treatment. ctDNA was analyzed using next-generation sequencing (targeted panel of 550 genes).

Results: Among the 489 pts with ctDNA analyzed at baseline, the most common alterations were in PIK3CA (28%), TP53 (19%), CCND1 (11%), MYC (8%), and GATA3 (8%). Poorer prognosis in both treatment groups was most evident in patients with TP53 and MYC alterations. A PFS treatment effect in favor of RIB was noted in all subsets, independent of biomarker status (Table). However, based on HR, a trend for more pronounced benefit with RIB + NSAI/TAM + GOS was observed in pts with altered CCND1, GATA3, and genes involved in receptor tyrosine kinase signaling.

Conclusions: RIB + NSAI/TAM + GOS provided PFS benefit irrespective of baseline biomarker alteration status and represents recommended first-line therapy for pts with premenopausal HR+/HER2- ABC. The genetic landscape of premenopausal ABC might modulate the magnitude of therapeutic benefit; these novel findings require confirmation in additional biomarker studies.

RIB + NSAI/TAM + GOSPBO + NSAI/TAM + GOSEvents, n/NPFS, median monthsEvents, n/NPFS, median, monthsHRa (95% CI)PIK3CAWT68/18024.6798/17012.190.45 (0.33-0.62)Alt38/6914.7546/7012.850.57(0.36-0.9)TP53WT78/20324.67109/19412.980.48(0.36-0.65)Alt28/469.2335/467.160.47(0.27-0.82)CCND1WT91/22122.11126/21712.880.52(0.39-0.68)Alt15/2811.2718/235.520.21(0.08-0.54)MYCWT90/22924.67125/22112.880.49(0.37-0.65)Alt16/207.3419/197.160.57(0.25-1.31)GATA3WT96/22622.11131/22212.850.52(0.39-0.68)Alt10/23NA13/185.520.18(0.05-0.62)Receptor tyrosine kinasesbWT76/19827.53114/20614.520.5(0.37-0.67)Alt30/5114.5530/345.650.26(0.14-0.47)8p11.23cWT84/21523.03124/21412.780.47(0.36-0.63)Alt22/3412.5220/269.130.51(0.26-1)8p11.23, chromosome 8, short arm, region 11.23; alt, alteration; CCND1, cyclin D1; CI, confidence interval; GATA3, GATA binding protein 3; GOS, goserelin; NA, not applicable; NSAI, nonsteroidal aromatase inhibitor; MYC, MYC proto-oncogene, bHLH transcription factor; PBO, placebo; PFS, progression-free survival; PIK3CA, phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit α; RIB, ribociclib; TAM, tamoxifen; TP53, tumor protein p53; WT, wild type.a HR for PFS of RIB vs PBO. b Receptor tyrosine kinase genes include EGFR, ERBB2, ERBB3, ERBB4, FGFR1, IGF1, IGF1R, KDR, KIT, PDGFRA, PDGFRB, and VEGFA. c Includes FGFR1, WHSC1L1, and ZNF703.

Citation Format: Aditya Bardia, Faye Su, Nadia Solovieff, Seock-Ah Im, Joohyuk Sohn, Keun Seok Lee, Saul Campos-Gomez, Kyung Hae Jung, Rafael Villanueva Vazquez, Yen-Shen Lu, Fabio Franke, Sara Hurvitz, Nadia Harbeck, Louis Chow, Karen Rodriguez Lorenc, Tetiana Taran, Naveen Babbar, Debu Tripathy. Genetic landscape of premenopausal HR+/HER2- advanced breast cancer (ABC) based on comprehensive circulating tumor DNA analysis and association with clinical outcomes in the Phase III MONALEESA-7 trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT141.

Phase III MONALEESA-7 trial of premenopausal patients with HR+/HER2− advanced breast cancer (ABC) treated with endocrine therapy ± ribociclib: Overall survival (OS) results

LBA1008

Background: The phase III MONALEESA-7 study (NCT02278120) is the first dedicated trial of endocrine therapy (ET) ± a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor in premenopausal patients (pts) with hormone receptor–positive (HR+)/HER2− ABC. The study met its primary endpoint of significantly longer progression-free survival (PFS) with ribociclib (RIB; a CDK4/6 inhibitor) + ET vs placebo (PBO) + ET (median, 23.8 vs 13.0 mo; HR, 0.55; P < 0.0001; Tripathy D, et al. Lancet Oncol. 2018). Methods: Premenopausal pts (N=672) with HR+/HER2− ABC were treated with RIB or PBO + goserelin and either a nonsteroidal aromatase inhibitor (NSAI; letrozole or anastrozole) or tamoxifen. This is the 2nd of 3 protocol-specified OS analyses (scheduled to occur after ≈ 189 deaths [75% of the planned total events]). OS was evaluated by Kaplan-Meier methods, and statistical comparison was made by 1-sided stratified log-rank test, with a protocol-defined Lan-DeMets (O’Brien-Fleming) stopping boundary of p < 0.01018 for superior efficacy. Results: The data cutoff for this prespecified interim analysis was Nov 30, 2018, and the median follow-up was 34.6 mo (min, 28.0 mo). At cutoff, 173 pts were continuing study treatment (RIB, n=116; PBO, n=57), and OS was evaluated after 192 deaths (RIB, n=83; PBO, n=109). RIB + ET demonstrated a significantly longer OS than PBO + ET (median, not reached vs 40.9 mo [95% CI, 37.80 mo-not evaluable]; HR, 0.712 [95% CI, 0.54-0.95]; p = 0.00973). The result crossed the prespecified stopping boundary for superior efficacy. Estimated OS rates with RIB + ET vs PBO + ET at 42 mo were 70.2% vs 46.0%, respectively. In pts who received an NSAI (n=495), RIB + ET demonstrated a consistent OS improvement vs PBO + ET (HR, 0.699 [95% CI, 0.50-0.98]). Posttreatment therapy use was balanced between treatment arms (RIB, 68.9%; PBO, 73.2%). Conclusions: RIB + ET demonstrated a clinically and statistically significant longer OS than ET alone in premenopausal pts with HR+/HER2− ABC. This is the first time that a CDK4/6 inhibitor or any targeted agent + ET has demonstrated significantly longer OS vs ET alone as initial endocrine-based therapy. Clinical trial information: NCT02278120.

In-depth gene expression analysis of premenopausal patients with HR+/HER2− advanced breast cancer (ABC) treated with ribociclib-containing therapy in the Phase III MONALEESA-7 trial

1018

Background: The Phase III MONALEESA-7 study (NCT02278120) is the first dedicated trial of endocrine therapy (ET) ± a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor in premenopausal patients (pts) with hormone receptor–positive (HR+)/human epidermal growth factor receptor 2–negative (HER2−) ABC. The study demonstrated that the addition of ribociclib (RIB) to a nonsteroidal aromatase inhibitor (NSAI) or tamoxifen (TAM) + goserelin (GOS) significantly extended progression-free survival (PFS; hazard ratio [HR] 0.55; Tripathy D, et al. Lancet Oncol. 2018). Here we present a gene expression analysis of baseline tumor mRNA from MONALEESA-7. Methods: Premenopausal pts with HR+/HER2− ABC were treated with RIB or placebo (PBO) + GOS with either an NSAI (letrozole or anastrozole) or TAM. Baseline archival tumor samples from 360 of 672 intent-to-treat (ITT) pts were evaluated for gene expression (RIB n = 185; PBO n = 175) using a customized NanoString nCounter® GX 800-gene panel containing relevant breast cancer, CDK, and proliferation pathway–related genes. Pt subgroups were classified as having low or high mRNA expression using median expression as the cutoff. Results: PFS benefit in the biomarker-assessed group was similar to that in the ITT population. A trend toward a more pronounced PFS benefit with RIB was observed in pts with high vs low expression of CCND1 (HR 0.38 vs 0.67, respectively), IGF1R (HR 0.33 vs 0.77), and ERBB3 (HR 0.33 vs 0.76). The PFS benefit seen with RIB also trended to be greater in pts with low vs high expression of CCNE1 (HR 0.38 vs 0.65, respectively) and MYC (HR 0.37 vs 0.69). The PFS benefit with RIB was similar in pts with high vs low expression of FGFR1 (HR 0.45 vs 0.61, respectively), ESR1 (HR 0.57 vs 0.57), and tumor proliferation genes, such as MKI67 (HR 0.50 vs 0.51). Conclusions: This is the first gene expression analysis of a large set of premenopausal pts with ABC. The benefit with RIB was generally consistent across gene expression subgroups, although the magnitude varied in certain subsets. This analysis suggests that there may be unique resistance mechanisms to ET ± CDK4/6 inhibitors in premenopausal pts with ABC. Clinical trial information: NCT02278120.

Clinical Pharmacology of Tisagenlecleucel in B-cell Acute Lymphoblastic Leukemia

PURPOSE

Tisagenlecleucel is an anti-CD19 chimeric antigen receptor (CAR19) T-cell therapy approved for the treatment of children and young adults with relapsed/refractory (r/r) B-cell acute lymphoblastic leukemia (B-ALL).

PATIENTS AND METHODS

We evaluated the cellular kinetics of tisagenlecleucel, the effect of patient factors, humoral immunogenicity, and manufacturing attributes on its kinetics, and exposure-response analysis for efficacy, safety and pharmacodynamic endpoints in 79 patients across two studies in pediatric B-ALL (ELIANA and ENSIGN).

RESULTS

Using quantitative polymerase chain reaction to quantify levels of tisagenlecleucel transgene, responders (N = 62) had ≈2-fold higher tisagenlecleucel expansion in peripheral blood than nonresponders (N = 8; 74% and 104% higher geometric mean Cmax and AUC0-28d, respectively) with persistence measurable beyond 2 years in responding patients. Cmax increased with occurrence and severity of cytokine release syndrome (CRS). Tisagenlecleucel continued to expand and persist following tocilizumab, used to manage CRS. Patients with B-cell recovery within 6 months had earlier loss of the transgene compared with patients with sustained clinical response. Clinical responses were seen across the entire dose range evaluated (patients ≤50 kg: 0.2 to 5.0 × 10⁶/kg; patients >50 kg: 0.1 to 2.5 × 10⁸ CAR-positive viable T cells) with no relationship between dose and safety. Neither preexisting nor treatment-induced antimurine CAR19 antibodies affected the persistence or clinical response.

CONCLUSIONS

Response to tisagenlecleucel was associated with increased expansion across a wide dose range. These results highlight the importance of cellular kinetics in understanding determinants of response to chimeric antigen receptor T-cell therapy.

Clinical Pharmacology of Tisagenlecleucel in B-cell Acute Lymphoblastic Leukemia

PURPOSE

Tisagenlecleucel is an anti-CD19 chimeric antigen receptor (CAR19) T-cell therapy approved for the treatment of children and young adults with relapsed/refractory (r/r) B-cell acute lymphoblastic leukemia (B-ALL).

PATIENTS AND METHODS

We evaluated the cellular kinetics of tisagenlecleucel, the effect of patient factors, humoral immunogenicity, and manufacturing attributes on its kinetics, and exposure-response analysis for efficacy, safety and pharmacodynamic endpoints in 79 patients across two studies in pediatric B-ALL (ELIANA and ENSIGN).

RESULTS

Using quantitative polymerase chain reaction to quantify levels of tisagenlecleucel transgene, responders (N = 62) had ≈2-fold higher tisagenlecleucel expansion in peripheral blood than nonresponders (N = 8; 74% and 104% higher geometric mean Cmax and AUC0-28d, respectively) with persistence measurable beyond 2 years in responding patients. Cmax increased with occurrence and severity of cytokine release syndrome (CRS). Tisagenlecleucel continued to expand and persist following tocilizumab, used to manage CRS. Patients with B-cell recovery within 6 months had earlier loss of the transgene compared with patients with sustained clinical response. Clinical responses were seen across the entire dose range evaluated (patients ≤50 kg: 0.2 to 5.0 × 10⁶/kg; patients >50 kg: 0.1 to 2.5 × 10⁸ CAR-positive viable T cells) with no relationship between dose and safety. Neither preexisting nor treatment-induced antimurine CAR19 antibodies affected the persistence or clinical response.

CONCLUSIONS

Response to tisagenlecleucel was associated with increased expansion across a wide dose range. These results highlight the importance of cellular kinetics in understanding determinants of response to chimeric antigen receptor T-cell therapy.

Phase III Randomized Study of Ribociclib and Fulvestrant in Hormone Receptor–Positive, Human Epidermal Growth Factor Receptor 2–Negative Advanced Breast Cancer: MONALEESA-3

Purpose

This phase III study evaluated ribociclib plus fulvestrant in patients with hormone receptor–positive/human epidermal growth factor receptor 2–negative advanced breast cancer who were treatment naïve or had received up to one line of prior endocrine therapy in the advanced setting.

Patients and Methods

Patients were randomly assigned at a two-to-one ratio to ribociclib plus fulvestrant or placebo plus fulvestrant. The primary end point was locally assessed progression-free survival. Secondary end points included overall survival, overall response rate, and safety.

Results

A total of 484 postmenopausal women were randomly assigned to ribociclib plus fulvestrant, and 242 were assigned to placebo plus fulvestrant. Median progression-free survival was significantly improved with ribociclib plus fulvestrant versus placebo plus fulvestrant: 20.5 months (95% CI, 18.5 to 23.5 months) versus 12.8 months (95% CI, 10.9 to 16.3 months), respectively (hazard ratio, 0.593; 95% CI, 0.480 to 0.732; P < .001). Consistent treatment effects were observed in patients who were treatment naïve in the advanced setting (hazard ratio, 0.577; 95% CI, 0.415 to 0.802), as well as in patients who had received up to one line of prior endocrine therapy for advanced disease (hazard ratio, 0.565; 95% CI, 0.428 to 0.744). Among patients with measurable disease, the overall response rate was 40.9% for the ribociclib plus fulvestrant arm and 28.7% for placebo plus fulvestrant. Grade 3 adverse events reported in ≥ 10% of patients in either arm (ribociclib plus fulvestrant v placebo plus fulvestrant) were neutropenia (46.6% v 0%) and leukopenia (13.5% v 0%); the only grade 4 event reported in ≥ 5% of patients was neutropenia (6.8% v 0%).

Conclusion

Ribociclib plus fulvestrant might represent a new first- or second-line treatment option in hormone receptor–positive/human epidermal growth factor receptor 2–negative advanced breast cancer.

Tisagenlecleucel in Children and Young Adults with B-Cell Lymphoblastic Leukemia

BACKGROUND

In a single-center phase 1-2a study, the anti-CD19 chimeric antigen receptor (CAR) T-cell therapy tisagenlecleucel produced high rates of complete remission and was associated with serious but mainly reversible toxic effects in children and young adults with relapsed or refractory B-cell acute lymphoblastic leukemia (ALL).

METHODS

We conducted a phase 2, single-cohort, 25-center, global study of tisagenlecleucel in pediatric and young adult patients with CD19+ relapsed or refractory B-cell ALL. The primary end point was the overall remission rate (the rate of complete remission or complete remission with incomplete hematologic recovery) within 3 months.

RESULTS

For this planned analysis, 75 patients received an infusion of tisagenlecleucel and could be evaluated for efficacy. The overall remission rate within 3 months was 81%, with all patients who had a response to treatment found to be negative for minimal residual disease, as assessed by means of flow cytometry. The rates of event-free survival and overall survival were 73% (95% confidence interval [CI], 60 to 82) and 90% (95% CI, 81 to 95), respectively, at 6 months and 50% (95% CI, 35 to 64) and 76% (95% CI, 63 to 86) at 12 months. The median duration of remission was not reached. Persistence of tisagenlecleucel in the blood was observed for as long as 20 months. Grade 3 or 4 adverse events that were suspected to be related to tisagenlecleucel occurred in 73% of patients. The cytokine release syndrome occurred in 77% of patients, 48% of whom received tocilizumab. Neurologic events occurred in 40% of patients and were managed with supportive care, and no cerebral edema was reported.

CONCLUSIONS

In this global study of CAR T-cell therapy, a single infusion of tisagenlecleucel provided durable remission with long-term persistence in pediatric and young adult patients with relapsed or refractory B-cell ALL, with transient high-grade toxic effects. (Funded by Novartis Pharmaceuticals; ClinicalTrials.gov number, NCT02435849 .).

A combined treatment of hydration and dynamical effects for the modeling of host-guest binding thermodynamics: the SAMPL5 blinded challenge

As part of the SAMPL5 blinded experiment, we computed the absolute binding free energies of 22 host-guest complexes employing a novel approach based on the BEDAM single-decoupling alchemical free energy protocol with parallel replica exchange conformational sampling and the AGBNP2 implicit solvation model specifically customized to treat the effect of water displacement as modeled by the Hydration Site Analysis method with explicit solvation. Initial predictions were affected by the lack of treatment of ionic charge screening, which is very significant for these highly charged hosts, and resulted in poor relative ranking of negatively versus positively charged guests. Binding free energies obtained with Debye-Hückel treatment of salt effects were in good agreement with experimental measurements. Water displacement effects contributed favorably and very significantly to the observed binding affinities; without it, the modeling predictions would have grossly underestimated binding. The work validates the implicit/explicit solvation approach employed here and it shows that comprehensive physical models can be effective at predicting binding affinities of molecular complexes requiring accurate treatment of conformational dynamics and hydration.

Molecular Alterations and Everolimus Efficacy in Human Epidermal Growth Factor Receptor 2-Overexpressing Metastatic Breast Cancers: Combined Exploratory Biomarker Analysis From BOLERO-1 and BOLERO-3

PURPOSE

Two recent phase III trials, BOLERO-1 and BOLERO-3 (Breast Cancer Trials of Oral Everolimus), evaluated the addition of everolimus to trastuzumab and chemotherapy in human epidermal growth factor receptor 2-overexpressing advanced breast cancer. The current analysis aimed to identify biomarkers to predict the clinical efficacy of everolimus treatment.

METHODS

Archival tumor samples from patients in BOLERO-1 and BOLERO-3 were analyzed using next-generation sequencing, immunohistochemistry, and Sanger sequencing.

RESULTS

Biomarker data were available for 549 patients. PIK3CA activating mutations and PTEN loss were reported in 30% and 16% of BOLERO-1 samples and in 32% and 12% of BOLERO-3 samples, respectively. PI3K pathway was hyperactive (PIK3CA mutations and/or PTEN loss and/or AKT1 mutation) in 47% of BOLERO-1 and 41% of BOLERO-3 samples. In both studies, differential progression-free survival (PFS) benefits of everolimus were consistently observed in patient subgroups defined by their PI3K pathway status. When analyzing combined data sets of both studies, everolimus was associated with a decreased hazard of progression in patients with PIK3CA mutations (hazard ratio [HR], 0.67; 95% CI, 0.45 to 1.00), PTEN loss (HR, 0.54; 95% CI, 0.31 to 0.96), or hyperactive PI3K pathway (HR, 0.67; 95% CI, 0.48 to 0.93). Patients with wild-type PIK3CA (HR, 1.10; 95% CI, 0.83 to 1.46), normal PTEN (HR, 1.00; 95% CI, 0.80 to 1.26), or normal PI3K pathway activity (HR, 1.19; 95% CI, 0.87 to 1.62) did not derive PFS benefit from everolimus.

CONCLUSION

This analysis, although exploratory, suggests that patients with human epidermal growth factor receptor 2-positive advanced breast cancer having tumors with PIK3CA mutations, PTEN loss, or hyperactive PI3K pathway could derive PFS benefit from everolimus.

Abstract P4-13-12: Everolimus plus trastuzumab and vinorelbine for trastuzumab-resistant, taxane-pretreated, HER2+ advanced breast cancer: Overall survival results from BOLERO-3

Background

PI3K/AKT/mTOR pathway activation due to PTEN loss may lead to trastuzumab (TRAS) resistance. mTOR inhibition has been shown to restore TRAS sensitivity in PTEN-deficient tumors. This provided the rationale for the BOLERO-3 trial which evaluated the combination of everolimus (EVE), an mTOR inhibitor, plus TRAS and a taxane in HER2+ advanced breast cancer (ABC). The addition of EVE to TRAS plus vinorelbine (VNB) led to a statistically significant prolongation of 1.2 months in median progression free survival (PFS) vs TRAS plus VNB in patients with TRAS-resistant and taxane-pretreated, HER2+ ABC (7.0 months vs 5.78 months; hazard ratio, 0.78; p=0.0067). The final overall survival (OS) analysis from this study is presented here.

Materials and methods

BOLERO-3 is a randomized, double-blind, placebo-controlled, phase 3 trial. Women with HER2+ ABC progressing on prior TRAS and taxane therapy were randomized (1:1) to receive either daily EVE (5 mg) or PBO plus weekly TRAS (2 mg/kg) and VNB (25 mg/m2), in 3-week cycles, stratified by previous lapatinib use. The primary endpoint was PFS by local investigator assessment. Overall survival was a key secondary endpoint.

Results

Overall, 569 patients were enrolled; 284 patients received EVE and 285 patients received PBO. As of April 1, 2015, after a median follow-up of 44.7 months, 388 deaths had occurred, 191 (67.3%) in the EVE arm and 197 (69.1%) in the PBO arm. The median OS in the EVE arm vs PBO arm was 23.5 months vs 24.1 months (HR = 0.96; 95% CI, 0.79-1.17; p = 0.3392). In the HR+ subgroup, the median OS with EVE was 23.5 months (vs 25.5 months with PBO; HR = 1.03; 95% CI, 0.79-1.35); in the HR subgroup, the median OS with EVE was 22.9 months (vs 23.1 months with PBO; HR = 0.86; 95% CI, 0.64-1.17). AEs leading to treatment discontinuation were reported in 81 (28.9%) vs 46 (16.3%) patients in the EVE vs PBO arms. Serious adverse events (SAEs) were reported in 122 (43.6%) vs 58 (20.6%) patients in the EVE vs PBO arms. Overall, 14 on-treatment deaths were observed, 7 (2.5%) in the EVE arm and 7 (2.5%) in the PBO arm; on-treatment deaths due to AEs were balanced between treatment arms (0.7% in each treatment arm). Types of post-progression therapies were balanced across both treatment arms.

Conclusions

In BOLERO-3, EVE showed a statistically significant prolongation of PFS. OS was similar in both treatment arms. The safety profile of EVE was comparable to that observed previously with EVE in breast cancer. (Funded by Novartis; BOLERO-3 ClinicalTrials.gov number, NCT01007942.)

Citation Format: Isaacs C, O'Regan R, Xu B, Masuda N, Arena F, Yap Y-S, Papai Z, Lang I, Armstrong A, Lerzo G, White M, Shen K, Zhang Y, Jappe A, Pacaud LB, Taran T, Ozguroglu M. Everolimus plus trastuzumab and vinorelbine for trastuzumab-resistant, taxane-pretreated, HER2+ advanced breast cancer: Overall survival results from BOLERO-3. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-13-12.

Correlative Analysis of Genetic Alterations and Everolimus Benefit in Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Advanced Breast Cancer: Results From BOLERO-2

PURPOSE

To explore the genetic landscape of tumors from patients enrolled on the BOLERO-2 trial to identify potential correlations between genetic alterations and efficacy of everolimus treatment. The BOLERO-2 trial has previously demonstrated that the addition of everolimus to exemestane prolonged progression-free survival by more than twofold in patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative, advanced breast cancer previously treated with nonsteroidal aromatase inhibitors.

PATIENTS AND METHODS

Next-generation sequencing was used to analyze genetic status of cancer-related genes in 302 archival tumor specimens from patients representative of the BOLERO-2 study population. Correlations between the most common somatic alterations and degree of chromosomal instability, and treatment effect of everolimus were investigated.

RESULTS

Progression-free survival benefit with everolimus was maintained regardless of alteration status of PIK3CA, FGFR1, and CCND1 or the pathways of which they are components. However, quantitative differences in everolimus benefit were observed between patient subgroups defined by the exon-specific mutations in PIK3CA (exon 20 v 9) or by different degrees of chromosomal instability in the tumor tissues.

CONCLUSION

The data from this exploratory analysis suggest that the efficacy of everolimus was largely independent of the most commonly altered genes or pathways in hormone receptor-positive, human epidermal growth factor receptor 2-negative breast cancer. The potential impact of chromosomal instabilities and low-frequency genetic alterations on everolimus efficacy warrants further investigation.

Combination of everolimus with trastuzumab plus paclitaxel as first-line treatment for patients with HER2-positive advanced breast cancer (BOLERO-1): a phase 3, randomised, double-blind, multicentre trial

BACKGROUND

mTOR inhibition reverses trastuzumab resistance via the hyperactivated PIK/AKT/mTOR pathway due to PTEN loss, by sensitising PTEN-deficient tumours to trastuzumab. The BOLERO-1 study assessed the efficacy and safety of adding everolimus to trastuzumab and paclitaxel as first-line treatment for patients with HER2-positive advanced breast cancer.

METHODS

In this phase 3, randomised, double-blind trial, patients were enrolled across 141 sites in 28 countries. Eligible patients were aged 18 years or older, with locally assessed HER2-positive advanced breast cancer, with Eastern Cooperative Oncology Group (ECOG) performance status of 0-1, who had not received previous trastuzumab or chemotherapy for advanced breast cancer within 12 months of randomisation, had measurable disease as per Response Evaluation Criteria in Solid Tumors (RECIST) or bone lesions in the absence of measurable disease, without previous systemic treatment for advanced disease except endocrine therapy. Patients were randomly assigned (2:1) with an interactive voice and web response system to receive either 10 mg everolimus once a day orally or placebo plus weekly trastuzumab intravenously at 4 mg/kg loading dose on day 1 with subsequent weekly doses of 2 mg/kg of each 4 week cycle plus paclitaxel intravenously at a dose of 80 mg/m(2) on days 1, 8, and 15 of each 4 week cycle. Randomisation was stratified according to previous use of trastuzumab and visceral metastasis. Patients and investigators were masked to the assigned treatments. Identity of experimental treatments was concealed by use of everolimus and placebo that were identical in packaging, labelling, appearance, and administration schedule. The two primary objectives were investigator-assessed progression-free survival in the full study population and in the subset of patients with hormone receptor-negative breast cancer at baseline; the latter was added during the course of the study, before unmasking based on new clinical and biological findings from other studies. All efficacy analyses were based on the intention-to-treat population. Enrolment for this trial is closed and results of the final progression-free survival analyses are presented here. This trial is registered with ClinicalTrials.gov, number NCT00876395.

FINDINGS

Between Sept 10, 2009, and Dec 16, 2012, 719 patients were randomly assigned to receive everolimus (n=480) or placebo (n=239). Median follow-up was 41·3 months (IQR 35·4-46·6). In the full population, median progression-free survival was 14·95 months (95% CI 14·55-17·91) with everolimus versus 14·49 months (12·29-17·08) with placebo (hazard ratio 0·89, 95% CI 0·73-1·08; p=0·1166). In the HR-negative subpopulation (n=311), median progression-free survival with everolimus was 20·27 months (95% CI 14·95-24·08) versus 13·08 months (10·05-16·56) with placebo (hazard ratio 0·66, 95% CI 0·48-0·91; p=0·0049); however, the protocol-specified significance threshold (p=0·0044) was not crossed. The most common adverse events with everolimus were stomatitis (314 [67%] of 472 patients in the everolimus group vs 77 [32%] of 238 patients in the placebo group), diarrhoea (267 [57%] vs 111 [47%] patients), and alopecia (221 [47%] vs 125 [53%]). The most frequently reported grade 3 or 4 adverse events in the everolimus group versus the placebo group were neutropenia (117 [25%] vs 35 [15%]), stomatitis (59 [13%] vs three [1%]), anaemia (46 [10%] vs six [3%]) and diarrhoea (43 [9%] vs 10 [4%]) On-treatment adverse event-related deaths were reported in 17 (4%) patients in the everolimus group and none in the placebo group.

INTERPRETATION

Although progression-free survival was not significantly different between groups in the full analysis population, the 7·2 months prolongation we noted with the addition of everolimus in the HR-negative, HER2-positive population warrants further investigation, even if it did not meet prespecified criteria for significance. The safety profile was generally consistent with what was previously reported in BOLERO-3. Proactive monitoring and early management of adverse events in patients given everolimus and chemotherapy is crucial.

FUNDING

Novartis Pharmaceuticals.

Everolimus plus exemestane for hormone-receptor-positive, human epidermal growth factor receptor-2-negative advanced breast cancer: overall survival results from BOLERO-2†

BACKGROUND

The BOLERO-2 study previously demonstrated that adding everolimus (EVE) to exemestane (EXE) significantly improved progression-free survival (PFS) by more than twofold in patients with hormone-receptor-positive (HR(+)), HER2-negative advanced breast cancer that recurred or progressed during/after treatment with nonsteroidal aromatase inhibitors (NSAIs). The overall survival (OS) analysis is presented here.

PATIENTS AND METHODS

BOLERO-2 is a phase III, double-blind, randomized international trial comparing EVE 10 mg/day plus EXE 25 mg/day versus placebo (PBO) + EXE 25 mg/day in postmenopausal women with HR(+) advanced breast cancer with prior exposure to NSAIs. The primary end point was PFS by local investigator assessment; OS was a key secondary end point.

RESULTS

At the time of data cutoff (3 October 2013), 410 deaths had occurred and 13 patients remained on treatment. Median OS in patients receiving EVE + EXE was 31.0 months [95% confidence interval (CI) 28.0-34.6 months] compared with 26.6 months (95% CI 22.6-33.1 months) in patients receiving PBO + EXE (hazard ratio = 0.89; 95% CI 0.73-1.10; log-rank P = 0.14). Poststudy treatments were received by 84% of patients in the EVE + EXE arm versus 90% of patients in the PBO + EXE arm. Types of poststudy therapies were balanced across arms, except for chemotherapy (53% EVE + EXE versus 63% PBO + EXE). No new safety concerns were identified.

CONCLUSIONS

In BOLERO-2, adding EVE to EXE did not confer a statistically significant improvement in the secondary end point OS despite producing a clinically meaningful and statistically significant improvement in the primary end point, PFS (4.6-months prolongation in median PFS; P < 0.0001). Ongoing translational research should further refine the benefit of mTOR inhibition and related pathways in this treatment setting.

TRIAL REGISTRATION NUMBER

NCT00863655.

Efficacy of everolimus with exemestane versus exemestane alone in Asian patients with HER2-negative, hormone-receptor-positive breast cancer in BOLERO-2

BACKGROUND

The addition of mTOR inhibitor everolimus (EVE) to exemestane (EXE) was evaluated in an international, phase 3 study (BOLERO-2) in patients with hormone-receptor-positive (HR(+)) breast cancer refractory to letrozole or anastrozole. The safety and efficacy of anticancer treatments may be influenced by ethnicity (Sekine et al. in Br J Cancer 99:1757-62, 2008). Safety and efficacy results from Asian versus non-Asian patients in BOLERO-2 are reported.

METHODS

Patients were randomized (2:1) to 10 mg/day EVE + EXE or placebo (PBO) + EXE. Primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival, response rate, clinical benefit rate, and safety.

RESULTS

Of 143 Asian patients, 98 received EVE + EXE and 45 received PBO + EXE. Treatment with EVE + EXE significantly improved median PFS versus PBO + EXE among Asian patients by 38 % (HR = 0.62; 95 % CI, 0.41-0.94). Median PFS was also improved among non-Asian patients by 59 % (HR = 0.41; 95 % CI, 0.33-0.50). Median PFS duration among EVE-treated Asian patients was 8.48 versus 4.14 months for PBO + EXE, and 7.33 versus 2.83 months, respectively, in non-Asian patients. The most common grade 3/4 adverse events (stomatitis, anemia, elevated liver enzymes, hyperglycemia, and dyspnea) occurred at similar frequencies in Asian and non-Asian patients. Grade 1/2 interstitial lung disease occurred more frequently in Asian patients. Quality of life was similar between treatment arms in Asian patients.

CONCLUSION

Adding EVE to EXE provided substantial clinical benefit in both Asian and non-Asian patients with similar safety profiles. This combination represents an improvement in the management of postmenopausal women with HR(+)/HER2(-) advanced breast cancer progressing on nonsteroidal aromatase inhibitors, regardless of ethnicity.

Everolimus for women with trastuzumab-resistant, HER2-positive, advanced breast cancer (BOLERO-3): a randomised, double-blind, placebo-controlled phase 3 trial

BACKGROUND

Disease progression in patients with HER2-positive breast cancer receiving trastuzumab might be associated with activation of the PI3K/Akt/mTOR intracellular signalling pathway. We aimed to assess whether the addition of the mTOR inhibitor everolimus to trastuzumab might restore sensitivity to trastuzumab.

METHODS

In this randomised, double-blind, placebo-controlled, phase 3 trial, we recruited women with HER2-positive, trastuzumab-resistant, advanced breast carcinoma who had previously received taxane therapy. Eligible patients were randomly assigned (1:1) using a central patient screening and randomisation system to daily everolimus (5 mg/day) plus weekly trastuzumab (2 mg/kg) and vinorelbine (25 mg/m(2)) or to placebo plus trastuzumab plus vinorelbine, in 3-week cycles, stratified by previous lapatinib use. The primary endpoint was progression-free survival (PFS) by local assessment in the intention-to-treat population. We report the final analysis for PFS; overall survival follow-up is still in progress. This trial is registered with ClinicalTrials.gov, number NCT01007942.

FINDINGS

Between Oct 26, 2009, and May 23, 2012, 569 patients were randomly assigned to everolimus (n=284) or placebo (n=285). Median follow-up at the time of analysis was 20.2 months (IQR 15.0-27.1). Median PFS was 7.00 months (95% CI 6.74-8.18) with everolimus and 5.78 months (5.49-6.90) with placebo (hazard ratio 0.78 [95% CI 0.65-0.95]; p=0.0067). The most common grade 3-4 adverse events were neutropenia (204 [73%] of 280 patients in the everolimus group vs 175 [62%] of 282 patients in the placebo group), leucopenia (106 [38%] vs 82 [29%]), anaemia (53 [19%] vs 17 [6%]), febrile neutropenia (44 [16%] vs ten [4%]), stomatitis (37 [13%] vs four [1%]), and fatigue (34 [12%] vs 11 [4%]). Serious adverse events were reported in 117 (42%) patients in the everolimus group and 55 (20%) in the placebo group; two on-treatment deaths due to adverse events occurred in each group.

INTERPRETATION

The addition of everolimus to trastuzumab plus vinorelbine significantly prolongs PFS in patients with trastuzumab-resistant and taxane-pretreated, HER2-positive, advanced breast cancer. The clinical benefit should be considered in the context of the adverse event profile in this population.

Incidence and time course of everolimus-related adverse events in postmenopausal women with hormone receptor-positive advanced breast cancer: insights from BOLERO-2

BACKGROUND

In the BOLERO-2 trial, everolimus (EVE), an inhibitor of mammalian target of rapamycin, demonstrated significant clinical benefit with an acceptable safety profile when administered with exemestane (EXE) in postmenopausal women with hormone receptor-positive (HR(+)) advanced breast cancer. We report on the incidence, time course, severity, and resolution of treatment-emergent adverse events (AEs) as well as incidence of dose modifications during the extended follow-up of this study.

PATIENTS AND METHODS

Patients were randomized (2:1) to receive EVE 10 mg/day or placebo (PBO), with open-label EXE 25 mg/day (n = 724). The primary end point was progression-free survival. Secondary end points included overall survival, objective response rate, and safety. Safety evaluations included recording of AEs, laboratory values, dose interruptions/adjustments, and study drug discontinuations.

RESULTS

The safety population comprised 720 patients (EVE + EXE, 482; PBO + EXE, 238). The median follow-up was 18 months. Class-effect toxicities, including stomatitis, pneumonitis, and hyperglycemia, were generally of mild or moderate severity and occurred relatively early after treatment initiation (except pneumonitis); incidence tapered off thereafter. EVE dose reduction and interruption (360 and 705 events, respectively) required for AE management were independent of patient age. The median duration of dose interruption was 7 days. Discontinuation of both study drugs because of AEs was higher with EVE + EXE (9%) versus PBO + EXE (3%).

CONCLUSIONS

Most EVE-associated AEs occur soon after initiation of therapy, are typically of mild or moderate severity, and are generally manageable with dose reduction and interruption. Discontinuation due to toxicity was uncommon. Understanding the time course of class-effect AEs will help inform preventive and monitoring strategies as well as patient education.

TRIAL REGISTRATION NUMBER

NCT00863655.

Abstract P3-15-03: Safety analysis of BOLERO-3: A phase 3 trial of daily everolimus (EVE) vs placebo (PBO), both with weekly trastuzumab (TRAS) and vinorelbine in trastuzumab-resistant, advanced breast cancer

Background: Activation of the PI3K/mTOR pathway is thought to be involved in resistance to TRAS. BOLERO-3 is a randomized phase 3, double-blind, placebo-controlled, international, clinical trial evaluating the addition of the mTOR inhibitor EVE (5 mg/day) to TRAS plus vinorelbine (25 mg/m2) in patients with HER2+ advanced breast cancer resistant to TRAS and who were previously treated with a taxane. A total of 569 adult women were randomized 1:1 to receive EVE (n = 284) or PBO (n = 285). Study treatment represented the 2nd, 3rd, or 4th line of chemotherapy-containing regimen for 83% of patients in the metastatic setting. The primary endpoint, progression-free survival based on local radiologic assessment, was significantly longer in the EVE arm versus PBO (HR = 0.78; P = .0067) at a median follow-up of 20 months.

Methods: Study drugs were continued until disease progression or unacceptable toxicity. Incidences of adverse events (AEs) were monitored continuously. Dose modifications and discontinuations were recorded.

Results: The median duration of exposure to study treatment was similar across treatment groups: 24.8 weeks for EVE, 25.1 weeks for TRAS, and 24.0 weeks for vinorelbine (EVE arm); and 22.9 weeks for PBO, 24.0 weeks for TRAS, and 23.1 weeks for vinorelbine (PBO arm). The AEs were consistent with known drug-safety profiles. Class-effect AEs with mTOR inhibitors (including stomatitis, rash, noninfectious pneumonitis, and hyperglycemia) were higher in the EVE arm and were mainly grade 1/2. Grade 3 class-effect AEs each occurred in &lt;15% of patients (stomatitis [13%], hyperglycemia [2%], and noninfectious pneumonitis [&lt;1%]). Grade 4 noninfectious pneumonitis (&lt;1%) was uncommon; there were no grade 4 events of stomatitis or hyperglycemia, and no grade 3/4 events of rash. The incidence and grade of hematologic AEs were increased in the EVE arm vs the PBO arm, including all grade neutropenia (81% vs 70%), anemia (49% vs 29%), febrile neutropenia (17% vs 4%) and thrombocytopenia (14% vs 2%); grade 3/4 hematologic AEs included neutropenia (grade 3: 35% vs 32%; grade 4: 38% vs 30%), anemia (grade 3: 17% vs 6%; grade 4: 2% vs &lt;1%), febrile neutropenia (grade 3: 11% vs 3%; grade 4: 5% vs 1%), and thrombocytopenia (grade 3: 3% vs &lt;1%; grade 4: 1% vs 0). The incidences and grades of changes in liver enzymes and hyperlipidemia were similar between arms. Serious AEs were reported in 42% of patients in the EVE arm and 20% of patients in the PBO arm (26% and 6% were attributed to study treatments, respectively). A higher percentage of patients discontinued treatment because of AEs in the EVE arm versus PBO (10% vs 5%). In all, 83% of patients required at least 1 EVE dose interruption and/or reduction; 96% of these were attributed to AEs. There were fewer deaths in the EVE arm (37%) compared with PBO (41%).

Conclusions: The safety of the combination of EVE, TRAS, and vinorelbine was considered manageable in this heavily pretreated patient population. Overall, the results from BOLERO-3 demonstrate that EVE can be combined with TRAS and chemotherapy to improve efficacy in TRAS-resistant HER2+ advanced breast cancer previously treated with a taxane.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-15-03.

Abstract P4-12-19: BOLERO-3: Everolimus plus trastuzumab and vinorelbine in Asian patients with HER2-positive metastatic breast cancer

Background: Resistance to trastuzumab may occur through activation of the PI3K/Akt/mTOR signaling pathway, the inhibition of which may restore trastuzumab sensitivity. BOLERO-3, a phase 3, double-blind, international trial involving 569 patients with trastuzumab-resistant, HER2-positive (HER2+), advanced breast cancer pretreated with a taxane, recently reported that adding everolimus (EVE; an mTOR inhibitor) to vinorelbine and trastuzumab significantly improved progression-free survival (PFS) vs placebo (PBO) plus vinorelbine and trastuzumab (hazard ratio [HR] = 0.78; log-rank P = .0067). As EVE pharmacokinetics and, therefore, clinical effects may be different in Asian patients, we analyzed the efficacy and safety data from BOLERO-3 for the Asian population.

Methods: Eligible women with trastuzumab-resistant, HER2+, advanced breast cancer who received prior taxane therapy were randomized (1:1) to EVE (5 mg/day) or matching PBO in combination with weekly vinorelbine (25 mg/m2) and trastuzumab (2 mg/kg after 4-mg/kg loading dose). The primary endpoint was PFS by investigator. Secondary endpoints included safety.

Results: Among 569 patients enrolled in this study, 166 (29%) patients were Asian; 88 and 78 were assigned to EVE or PBO arms, respectively. In this subpopulation, adding EVE to vinorelbine and trastuzumab prolonged median PFS compared with the PBO arm (8.3 vs 6.8 months, respectively; HR = 0.83; 95% confidence interval, 0.59 - 1.18). In general, the incidence of all grade adverse events was similar for Asian versus non-Asian patients in the EVE arm (stomatitis, 71% vs 59%; pneumonitis, 7% vs 5%; and infections, 58% vs 70%) and the PBO arm (stomatitis, 31% vs 26%; pneumonitis, 1% vs 4%; and infections, 48% vs 49%). Serious adverse events had a low incidence and included febrile neutropenia (9.1%), neutropenia (2.3%), stomatitis (2.3%), anemia (2.3%), and cataract (2.3%) as the most common among Asian patients in the EVE arm. The incidence of serious pneumonitis was low: Asian (1.1%) versus non-Asian patients (0%) in the EVE arm and 0% versus 1.5%, respectively, in the PBO arm.

Conclusions: Asian patients in the BOLERO-3 trial treated with EVE plus vinorelbine and trastuzumab showed PFS benefits similar to the overall population and had a comparable manageable safety profile. Thus, EVE in combination with vinorelbine and trastuzumab may be considered as a new therapeutic option for Asian women with trastuzumab-resistant, HER2+, advanced breast cancer progressing after taxane-based therapies.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-12-19.

Abstract P4-12-18: BOLERO-3: Quality-of-life maintained in patients with metastatic breast cancer treated with everolimus plus trastuzumab plus vinorelbine

Background: Activation of the PI3K/mTOR pathway is implicated in resistance to trastuzumab. Accordingly, the BOLERO-3 study evaluated the efficacy of adding everolimus (EVE), an mTOR inhibitor, to vinorelbine and trastuzumab. At the final progression-free survival (PFS) analysis, EVE significantly improved PFS vs PBO (hazard ratio [HR] = 0.78; log-rank P = .0067) but EVE-treated patients had higher rate of grade 3/4 toxicity. To further qualify the benefit:risk of adding EVE to trastuzumab-based therapy, per-protocol, patient-reported, health-related quality-of-life (HRQoL) data were analyzed.

Methods: BOLERO-3 is a randomized phase 3, double-blind, placebo-controlled, international multicenter trial. Taxane-pretreated patients (N = 569) with trastuzumab-resistant, HER2+, advanced breast cancer were randomized (1:1) to treatment with EVE or placebo (PBO) plus vinorelbine and trastuzumab. The European Organisation for Research and Treatment of Cancer (EORTC) quality-of-life questionnaire C30 (QLQ-C30) (including the breast cancer-specific BR23 module) was administered at baseline and every 6 weeks thereafter until progression. The QLQ-C30 consists of 30 items combined into 15 subscales, including Global Health Status and functional subscales, where higher scores (range, 0 to 100) indicate better HRQoL. Time to definitive deterioration (TTD) based on a 10% decrease from baseline for GHS and for the physical, emotional, and social function subscales was determined using the Kaplan-Meier method. Treatment arms were compared using a 2-sided log-rank test stratified by prior use of lapatinib.

Results: Overall, there was no significant difference in median TDD of HRQoL between treatment arms. The median TTD in global health status score was 8.3 months for EVE (95% confidence interval [CI], 6.9-11.5) vs 7.3 months for PBO (95% CI, 5.6-10.4; P = .8386). The median TTD in the physical, emotional, and social function subscale scores showed no significant difference between arms. For example, median TTD in the physical function subscale score was 12.0 months (95% CI, 8.3-14.1) for EVE vs 12.5 months (95% CI, 8.3-20.9) for PBO (P = .4251), and median TTD in the emotional function subscale score was 15.2 months (95% CI, 9.2-17.3) for EVE vs 12.5 months (95% CI, 9.7-16.4) for PBO (P = .8140).

Conclusions: These analyses demonstrate that, despite increased frequency of adverse events observed with the addition of EVE to the standard treatment of vinorelbine and trastuzumab, overall and functional HRQoL scores were not negatively impacted in patients with trastuzumab-resistant, HER2+, advanced breast cancer.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-12-18.

Abstract P2-16-17: Characterization of response to everolimus (EVE) in BOLERO-2: A phase 3 trial of EVE plus exemestane (EXE) in postmenopausal women with HR+, HER2- advanced breast cancer

Introduction: The BOLERO-2 trial demonstrated that combining the oral mammalian target of rapamycin (mTOR) inhibitor, EVE, with the steroidal aromatase inhibitor, EXE, more than doubled median progression-free survival (PFS) compared with placebo (PBO) plus EXE in postmenopausal women with hormone-receptor-positive (HR+), human epidermal growth factor receptor-2-negative (HER2−) breast cancer (BC) who relapsed or progressed following a nonsteroidal aromatase inhibitor (NSAI). Patients also achieved responses per Response Evaluation Criteria in Solid Tumors (RECIST) during treatment with EVE+EXE.

Methods: The phase 3, double-blind, BOLERO-2 trial randomized postmenopausal women with HR+ BC progressing or recurring after NSAIs in a 2:1 manner to EVE 10 mg once daily plus EXE 25 mg once daily (EVE+EXE; n = 485) or placebo (PBO) plus EXE (PBO+EXE; n = 239). The primary endpoint was PFS by local assessment. Overall response rate (ORR; complete + partial response per investigator assessment based on RECIST 1.0) and duration of overall response were secondary endpoints. In addition, best percentage change from baseline in sum of longest diameters of target lesions was assessed.

Results: At the time of final PFS analyses at 18 months’ median follow-up, ORR was significantly higher in the EVE+EXE arm compared with the PBO+EXE arm (12.6% vs 1.7%, respectively, by local assessment; P&lt;.0001). Among patients with measurable disease at baseline, 71% in the EVE+EXE arm had a decrease in the sum of longest diameters of target lesions compared with baseline vs 30% in the PBO+EXE arm. Median duration of overall response was 10.5 months (95% confidence interval [CI]: 8.2, 21.9 months) for EVE+EXE and 6.9 months (95% CI: 4.2, 6.9 months) for PBO+EXE. Of note, only 4 patients in the PBO+EXE arm had an objective response to treatment.

Conclusions: In addition to PFS, the combination of EVE plus EXE significantly improved ORR vs PBO+EXE in patients with HR+, HER2− advanced BC progressing during or after NSAI therapy. Furthermore, greater than two-thirds of patients treated with EVE+EXE experienced tumor shrinkage during treatment. These results further support the rationale for combining EVE with EXE to improve clinical outcomes in HR+, HER2− advanced BC progressing after NSAI therapy.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-16-17.

Safety and efficacy of everolimus with exemestane vs. exemestane alone in elderly patients with HER2-negative, hormone receptor-positive breast cancer in BOLERO-2

BACKGROUND

Postmenopausal women with hormone receptor-positive (HR(+)) breast cancer in whom disease progresses or there is recurrence while taking a nonsteroidal aromatase inhibitor (NSAI) are usually treated with exemestane (EXE), but no single standard of care exists in this setting. The BOLERO-2 trial demonstrated that adding everolimus (EVE) to EXE improved progression-free survival (PFS) while maintaining quality of life when compared with EXE alone. Because many women with HR(+) advanced breast cancer are elderly, the tolerability profile of EVE plus EXE in this population is of interest.

PATIENTS AND METHODS

BOLERO-2, a phase III randomized trial, compared EVE (10 mg/d) and placebo (PBO), both plus EXE (25 mg/d), in 724 postmenopausal women with HR(+) advanced breast cancer recurring/progressing after treatment with NSAIs. Safety and efficacy data in elderly patients are reported at 18-month median follow-up.

RESULTS

Baseline disease characteristics and treatment histories among the elderly subsets (≥ 65 years, n = 275; ≥ 70 years, n = 164) were generally comparable with younger patients. The addition of EVE to EXE improved PFS regardless of age (hazard ratio, 0.59 [≥ 65 years] and 0.45 [≥ 70 years]). Adverse events (AEs) of special interest (all grades) that occurred more frequently with EVE than with PBO included stomatitis, infections, rash, pneumonitis, and hyperglycemia. Elderly EVE-treated patients had similar incidences of these AEs as did younger patients but had more on-treatment deaths.

CONCLUSION

Adding EVE to EXE offers substantially improved PFS over EXE and was generally well tolerated in elderly patients with HR(+) advanced breast cancer. Careful monitoring and appropriate dose reductions or interruptions for AE management are recommended during treatment with EVE in this patient population.

Health-related quality of life and disease symptoms in postmenopausal women with HR(+), HER2(-) advanced breast cancer treated with everolimus plus exemestane versus exemestane monotherapy

OBJECTIVE

Everolimus (EVE)+exemestane (EXE; n = 485) more than doubled median progression-free survival versus placebo (PBO) + EXE (n = 239), with a manageable safety profile and no deterioration in health-related quality-of-life (HRQOL) in patients with hormone-receptor-positive (HR(+)) advanced breast cancer (ABC) who recurred or progressed on/after nonsteroidal aromatase inhibitor (NSAI) therapy. To further evaluate EVE + EXE impact on disease burden, we conducted additional post-hoc analyses of patient-reported HRQOL.

RESEARCH DESIGN AND METHODS

HRQOL was assessed using EORTC QLQ-C30 and QLQ-BR23 questionnaires at baseline and every 6 weeks thereafter until treatment discontinuation because of disease progression, toxicity, or consent withdrawal. Endpoints included the QLQ-C30 Global Health Status (QL2) scale, the QLQ-BR23 breast symptom (BRBS), and arm symptom (BRAS) scales. Between-group differences in change from baseline were assessed using linear mixed models with selected covariates. Sensitivity analysis using pattern-mixture models determined the effect of study discontinuation on/before week 24. Treatment arms were compared using differences of least squares mean (LSM) changes from baseline and 95% confidence intervals (CIs) at each timepoint and overall.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov: NCT00863655.

MAIN OUTCOME MEASURES

Progression-free survival, survival, response rate, safety, and HRQOL.

RESULTS

Linear mixed models (primary model) demonstrated no statistically significant overall difference between EVE + EXE and PBO + EXE for QL2 (LSM difference = -1.91; 95% CI = -4.61, 0.78), BRBS (LSM difference = -0.18; 95% CI = -1.98, 1.62), or BRAS (LSM difference = -0.42; 95% CI = -2.94, 2.10). Based on pattern-mixture models, patients who dropped out early had worse QL2 decline on both treatments. In the expanded pattern-mixture model, EVE + EXE-treated patients who did not drop out early had stable BRBS and BRAS relative to PBO + EXE.

KEY LIMITATIONS

HRQOL data were not collected after disease progression.

CONCLUSIONS

These analyses confirm that EVE + EXE provides clinical benefit without adversely impacting HRQOL in patients with HR(+) ABC who recurred/progressed on prior NSAIs versus endocrine therapy alone.

A phase 2 study of everolimus combined with trastuzumab and paclitaxel in patients with HER2-overexpressing advanced breast cancer that progressed during prior trastuzumab and taxane therapy

Increased activation of the PI3K/Akt/mTOR pathway is a common factor in putative mechanisms of trastuzumab resistance, resulting in dysregulation of cell migration, growth, proliferation, and survival. Data from preclinical and phase 1/2 clinical studies suggest that adding everolimus (an oral mTOR inhibitor) to trastuzumab plus chemotherapy may enhance the efficacy of, and restore sensitivity to, trastuzumab-based therapy. In this phase 2 multicenter study, adult patients with HER2-positive advanced breast cancer resistant to trastuzumab and pretreated with a taxane received everolimus 10 mg/day in combination with paclitaxel (80 mg/m² days 1, 8, and 15 every 4 weeks) and trastuzumab (4 mg/kg loading dose followed by 2 mg/kg weekly), administered in 28-day cycles. Endpoints included overall response rate (ORR), progression-free survival (PFS), overall survival (OS), and safety. Fifty-five patients were enrolled; one remained on study treatment at the time of data cutoff. The median number of prior chemotherapy lines for advanced disease was 3.5 (range 1–11). The ORR was 21.8 %, the clinical benefit rate was 36.4 %, the median PFS estimate was 5.5 months (95 % confidence interval [CI]: 4.99–7.69 months), and the median OS estimate was 18.1 months (95 % CI: 12.85–24.11 months). Hematologic grade 3/4 adverse events (AEs) included neutropenia (25.5 % grade 3, 3.6 % grade 4), anemia (7.3 % grade 3), and thrombocytopenia (5.5 % grade 3, 1.8 % grade 4). Nonhematologic grade 3/4 AEs included stomatitis (20.0 %), diarrhea (5.5 %), vomiting (5.5 %), fatigue (5.5 %), and pneumonia (5.5 %), all grade 3. These findings suggest that the combination of everolimus plus trastuzumab and paclitaxel is feasible, with promising activity in patients with highly resistant HER2-positive advanced breast cancer. This combination is currently under investigation in the BOLERO-1 phase 3 trial.