Intrinsic Subtype and Overall Survival of Patients with Advanced HR+/HER2- Breast Cancer Treated with Ribociclib and ET: Correlative Analysis of MONALEESA-2, -3, -7

PURPOSE

The MONALEESA-2, -3, -7 trials demonstrated statistically significant and clinically meaningful progression-free survival and overall survival (OS) benefits with ribociclib plus endocrine therapy (ET) versus ET alone in hormone receptor-positive, HER2-negative (HR+/HER2-) advanced breast cancer (ABC). Understanding the association of intrinsic subtypes with survival outcomes could potentially guide treatment decisions. Here, we evaluated the association of intrinsic subtypes with OS in MONALEESA-2, -3, -7.

EXPERIMENTAL DESIGN

Tumor samples from MONALEESA-2, -3, -7 underwent PAM50-based subtyping. The relationship between subtypes and OS was assessed using univariable and multivariable Cox proportional hazards models. Multivariable models were adjusted for clinical prognostic factors.

RESULTS

Overall, 990 tumors (among 2,066 patients) from ribociclib (n = 580) and placebo (n = 410) arms were profiled. Subtype distribution was luminal A, 54.5%; luminal B, 28.0%; HER2-enriched (HER2E) 14.6%; and basal-like, 2.8%; and was consistent across treatment arms. The luminal A subtype had the best OS outcomes in both arms, while basal-like had the worst. Patients with HER2E (HR, 0.60; P = 0.018), luminal B (HR, 0.69; P = 0.023), and luminal A (HR, 0.75; P = 0.021) subtypes derived OS benefit with ribociclib. Patients with basal-like subtype did not derive benefit from ribociclib (HR, 1.92; P = 0.137); however, patient numbers were small (n = 28).

CONCLUSIONS

The prognostic value of intrinsic subtypes for OS was confirmed in this pooled analysis of the MONALEESA trials (largest dataset in HR+/HER2- ABC). While basal-like subtype did not benefit, a consistent OS benefit was observed with ribociclib added to ET across luminal and HER2E subtypes.

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 P4-01-42: Pooled analysis of post-progression treatments after first-line ribociclib + endocrine therapy in patients with HR+/HER2− advanced breast cancer in the MONALEESA-2, -3, and -7 studies

Background: The MONALEESA (ML) studies showed significant PFS & OS benefits for 1L ribociclib (RIB) + endocrine therapy (ET) in patients (pts) with pre/peri & postmenopausal advanced breast cancer. The benefit of RIB beyond study treatment (tx) was also observed, with improvements in PFS2 & delays in time to 1st subsequent chemotherapy (CT). While there is currently no preferred tx for the next line post-progression on a CDK4/6 inhibitor (CDK4/6i), except alpelisib in pts with a PIK3CA mutation, guidelines encourage multiple lines of ET or ET-based therapies before switching to CT (except for visceral crisis). This pooled exploratory analysis of the ML studies examined outcomes of various tx strategies post progression on RIB + ET.

Methods: Data from pts receiving 1L therapy in ML-2, -3, & -7 (NSAI cohort only & excluding pts with early relapse [≤ 12 mo after end of (neo)adjuvant ET] whose prognosis is closer to that of 2L pts) were pooled & pts receiving 1st subsequent therapies after progression were analyzed. Three groups of subsequent therapies were assessed: ET only, CT, & targeted therapy. Subsequent CT comprises CT +/- any other therapy; targeted therapy includes CDK4/6i, mTORi, PI3Ki, AKTi, etc, +/- ET. Subsequent CT & targeted therapy groups are mutually exclusive. Median duration of study tx, 1st subsequent therapy, & OS (from randomization to death) were analyzed by KM methods. Weighted Cox regressions were performed using inversed propensity scoring matching method (inverse probability tx weighting [IPTW]) to ensure compatible pt characteristics between tx arms. These are not randomized comparisons; only baseline characteristics were used for the estimation of propensity scores in the IPTW, imbalance of prognostic factors at progression may exist.

Results: Median follow-up time was 74 mo. 461 pts treated with RIB (81%) & 440 (86%) with PBO discontinued study tx & received a subsequent therapy. In the RIB arms, the most common 1st subsequent therapies were ET only (40%), CT (29%), combination with targeted therapy (28%), & other (4%); for the PBO arms, 34% received CT as a 1st subsequent therapy & 31% each received ET only or combination with targeted therapy (5% received other). In 14% & 20% of pts in the RIB & PBO arms, the 1st subsequent therapy was a CDK4/6i, of these 31% & 12% were RIB. In general, regardless of type of 1st subsequent therapy, the duration of both the study tx & the 1st subsequent therapy was longer for pts treated with RIB vs PBO (Table). In both RIB & PBO arms, pts who received subsequent CT had the shortest duration on study tx, whereas those who received subsequent targeted therapy combination had the longest. Among pts on 1L RIB + ET, after matching pre-randomization baseline characteristics, subsequent CDK4/6i use was associated with the longest mOS (84 [84-NE] mo), followed by ET only (60 [51-68] mo), then a non-CDK4/6i targeted therapy (52 [43-72] mo); post-progression CT was associated with the shortest mOS (37 [32-48] mo).

Conclusions: This large, pooled analysis of the ML studies shows that, in general, duration of any subsequent therapy was numerically longer post-1L RIB + ET vs PBO + ET, & subsequent CT was used less frequently for pts on RIB vs PBO. Both findings confirm that upfront tx with RIB does not worsen pt outcomes. This trend in enhancement of outcomes of subsequent therapies seen with 1L RIB suggests a post-tx effect that merits further exploration.

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 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.

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 < .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 P1-18-11: Analysis of first-line (1L) patients (pts) with de novo disease vs late relapse and all pts with vs without prior chemotherapy (CT) in the MONALEESA-3 (ML-3) trial

Background: The phase 3 ML-3 trial demonstrated significant OS benefit for ribociclib (RIB) + fulvestrant (FUL) over placebo (PBO) + FUL as first- or second- line therapy in postmenopausal pts with HR+/HER2- advanced breast cancer (ABC). Prior treatment ([neo]adjuvant or advanced setting) may impact subsequent therapy outcomes, including OS; therefore, understanding the potential effect of prior treatment is of high clinical interest. Here, we present PFS and OS data from 2 subgroup analyses in ML-3: 1L pts with de novo disease vs late relapse and all pts with vs without prior CT. Methods: ML-3 (NCT02422615) enrolled postmenopausal pts who were randomized 2:1 to receive RIB + FUL or PBO + FUL. Pts with prior ET ([neo]adjuvant or ≤1 prior ET for ABC) and no CT for ABC were included. Pts with de novo disease were defined as initially diagnosed as ABC with no prior treatment for ABC. Pts with late relapse were defined as those who relapsed >12 months from completion of (neo)adjuvant ET with no prior treatment for ABC. Since prior CT for ABC was not allowed in ML-3, the prior CT analysis compares pts with prior (neo)adjuvant CT vs those without prior (neo)adjuvant CT. Results: The data cutoff was October 30, 2020. Within the 1L population, in the de novo vs late relapse analysis, 132 pts (RIB: n = 91; PBO: n = 41) had de novo disease, and 153 had late relapse (RIB: n = 98; PBO: n = 55). Baseline characteristics were generally balanced between the de novo and late relapse groups, with some notable exceptions: a higher proportion of pts with de novo disease were aged <65 years (52.3% vs 41.8%) and a lower proportion had visceral disease (53.0% vs 63.4%). In the late relapse group, 70.6% had prior (neo)adjuvant CT. De novo disease or late relapse did not appear to be prognostic as both PFS and OS were generally comparable between those 2 groups among pts treated with RIB or those treated with PBO (Table). Treatment with RIB + FUL demonstrated consistent PFS and OS benefits over PBO + FUL in both pts with de novo disease and those with late relapse. In the prior CT analysis, 391 pts (RIB: n = 265; PBO: n = 126) had prior CT (41.4% in 1L and 55.5% in 2L/early relapse [3.1% data missing]) and 334 (RIB: n = 219; PBO: n = 115) had no prior CT (60.8% in 1L, 38.9% in 2L/early relapse [0.3% data missing]). Baseline characteristics were generally balanced between pts with and without prior CT, with some exceptions: a higher proportion of pts with prior CT were aged <65 years (62.1% vs 42.8%) and had prior ET in any setting (86.4% vs 53.0%). Pts without prior CT had longer median PFS and OS compared with those who had prior CT in both the RIB and PBO arms (OS without vs with prior CT treated with RIB: HR, 0.68 [95% CI, 0.52-0.89]; PBO: HR, 0.72 [95% CI, 0.52-1.00]). Treatment with RIB + FUL demonstrated consistent PFS and OS benefits over PBO + FUL in both pts with prior CT and those without (OS for RIB vs PBO with prior CT: HR, 0.76 [95% CI, 0.58-1.01]; without prior CT: HR, 0.70 [95% CI, 0.50-0.97]). Conclusions: This exploratory analysis demonstrated that metastatic presentation (de novo vs late relapse) was not prognostic for disease outcomes; however, prior CT exposure, even in (neo)adjuvant, was associated with poorer PFS and OS. The addition of RIB showed consistent PFS and OS benefit across all subgroups in this analysis. Particularly, the addition of RIB resulted in a consistent and clinically meaningful PFS and OS benefit with a decrease in relative risk of death by 24% in pts with prior exposure to CT.

RIB + FULPBO + FULHR (RIB vs PBO)De novo/late relapseMedian PFS (95% CI), monthsDe novo35.6. (27.1-42.0)22.1. (14.6-33.1)0.55. (0.35-0.86)Late relapse35.8. (20.0-44.4)22.0. (16.5-27.7)0.60. (0.40-0.89)HR (de novo vs late elapse)0.93. (0.64-1.36)0.996. (0.63-1.57)Median OS (95% CI), monthsDe novo59.9. (52.7-NE)52.9. (39.6-NE)0.67. (0.38-1.19)Late relapseNE. (54.9-NE)52.3. (40.4-NE)0.69. (0.42-1.13)HR (de novo vs late relapse)0.899. (0.552-1.465)0.91. (0.51-1.62)Prior (neo)adjuvant CTMedian PFS (95% CI), monthsWithout prior CT28.3. (23.3-35.6)17.5. (13.6-21.9)0.60. (0.46-0.78)With prior CTa17.9. (14.3-19.9)10.8. (7.2-12.3)0.61. (0.48-0.78)HR (without vs with prior CT)0.76. (0.60-0.94)0.72. (0.55-0.95)Median OS (95% CI), monthsWithout prior CTNE (54.9-NE)44.9 (38.5-58.1)0.70. (0.50-0.97)With prior CTa43.0 (39.1-51.2)40.1 (30.3-48.6)0.76. (0.58-1.01)HR (without vs with prior CT)0.68 (0.52-0.89)0.72 (0.52-1.00)NE, not estimable a Includes 4 patients who received prior CT for ABC (protocol violation).

Citation Format: Michelino De Laurentiis, Matteo Lambertini, Stephen Chia, Hope S Rugo, Katarina Petrakova, Cristian Villanueva, Sara Hurvitz, J. Thaddeus Beck, Agnes Lteif, Sina Haftchenary, Uday Deore, Jiwen Wu, Nagi El-Saghir. Analysis of first-line (1L) patients (pts) with de novo disease vs late relapse and all pts with vs without prior chemotherapy (CT) in the MONALEESA-3 (ML-3) trial [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 P1-18-11.

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 > 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 < 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 < .001), being significantly higher in the LumB (P < .001) and HER2E (P < .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.

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.

Overall survival (OS) in patients (pts) with advanced breast cancer (ABC) with visceral metastases (mets), including those with liver mets, treated with ribociclib (RIB) plus endocrine therapy (ET) in the MONALEESA (ML) -3 and -7 trials

1054

Background: In the Phase III ML-3 (NCT02422615) and ML-7 (NCT02278120) trials, RIB + ET demonstrated a significant OS benefit (ML-3: HR, 0.72, P = 0.00455; ML-7: HR, 0.71, P = 0.00973) over placebo (PBO) + ET in pts with HR+/HER2- ABC (Im et al. N Engl J Med. 2019; Slamon et al. N Engl J Med. 2019). The presence of visceral mets generally portends a poor prognosis, which is especially poor in pts with liver mets (He et al. Ann Oncol. 2019). Here we report OS in pts with visceral mets with a focus on those with liver mets in ML-3 and ML-7. Methods: In ML-3, postmenopausal pts were randomized 2:1 to receive RIB + fulvestrant (FUL) or PBO + FUL as first- (1L) or second-line (2L) treatment. In ML-7, premenopausal pts were randomized 1:1 to receive RIB + ET or PBO + ET (this analysis included only pts who received an NSAI as ET partner to match approved indication). Results: Visceral mets were identified in 293 pts (60.5%) in the RIB arm and 147 (60.7%) in the PBO arm in ML-3 and 150 (44.8%) and 142 pts (42.1%), respectively, in ML-7. In ML-3, the median age of pts with visceral mets was 63 and 65 years in the RIB and PBO arms, and in ML-7 it was 42.5 and 45.0 years, respectively. In ML-3, 214 pts with visceral mets received 1L therapy (RIB, n = 137; PBO, n = 77), while 219 pts received 2L therapy or had early relapse (RIB, n = 151; PBO, n = 68). Lung and liver were the most common sites of visceral mets for pts in ML-3 (49.8% and 44.8%, respectively) and ML-7 (51.4% and 58.2%, respectively). OS HRs in pts with visceral mets were consistent with the benefit in the overall pt populations and suggested a particularly substantial OS benefit in pts with liver mets (HR for liver mets group in ML-3, 0.629 [95% CI, 0.421-0.942]; HR in ML-7, 0.531 [95% CI, 0.321-0.877]; Table). No new safety signals were observed. Conclusions: Approximately half of the pts in ML-3 and ML-7 had visceral mets. The OS data in these pts are consistent with the benefit observed with RIB in the overall populations of each trial. In pts with liver mets, a group with an especially poor prognosis, RIB + ET demonstrated a substantial OS benefit compared with PBO + ET. Clinical trial information: NCT02422615; NCT02278120 . [Table: see text]

Time course and management of key adverse events during the randomized phase III SOLAR-1 study of PI3K inhibitor alpelisib plus fulvestrant in patients with HR-positive advanced breast cancer

BACKGROUND

Alpelisib (α-selective phosphatidylinositol 3-kinase inhibitor) plus fulvestrant is approved in multiple countries for men and postmenopausal women with PIK3CA-mutated, hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer following progression on or after endocrine therapy. A detailed understanding of alpelisib's safety profile should inform adverse event (AE) management and enhance patient care.

PATIENTS AND METHODS

AEs in the phase III SOLAR-1 trial were assessed in patients with and without PIK3CA mutations. The impact of protocol-specified AE-management recommendations was evaluated, including an amendment to optimize hyperglycemia and rash management.

RESULTS

Patients were randomly assigned to receive fulvestrant plus alpelisib (n = 284) or placebo (n = 287). The most common grade 3/4 AEs with alpelisib were hyperglycemia (grade 3, 32.7%; grade 4, 3.9%), rash (grade 3, 9.9%), and diarrhea (grade 3, 6.7%). Median time to onset of grade ≥3 toxicity was 15 days (hyperglycemia, based on fasting plasma glucose), 13 days (rash), and 139 days (diarrhea). Metformin alone or in combination with other antidiabetic agents was used by most patients (87.1%) with hyperglycemia. Preventive anti-rash medication resulted in lower incidence (any grade, 26.7% versus 64.1%) and severity of rash (grade 3, 11.6% versus 22.7%) versus no preventative medication. Discontinuations due to grade ≥3 AEs were lower following more-detailed AE management guidelines (7.9% versus 18.1% previously). Patients with PIK3CA mutations had a median alpelisib dose intensity of 248 mg/day. Median progression-free survival with alpelisib was 12.5 and 9.6 months for alpelisib dose intensities of ≥248 mg/day and <248 mg/day, respectively, compared with 5.8 months with placebo.

CONCLUSIONS

Hyperglycemia and rash occurred early during alpelisib treatment, while diarrhea occurred at a later time point. Early identification, prevention, and intervention, including concomitant medications and alpelisib dose modifications, resulted in less severe toxicities. Reductions in treatment discontinuations and improved progression-free survival at higher alpelisib dose intensities support the need for optimal AE management. CLINICALTRIALS.

GOV ID

NCT02437318.

Alpelisib (ALP) with fulvestrant (FUL) in patients (pts) with PIK3CA-mutated hormone receptor-positive (HR+), human epidermal growth factor receptor-2-negative (HER2-) advanced breast cancer (ABC): Primary or secondary resistance to prior endocrine therapy (ET) in the SOLAR-1 trial

1038

Background: A contributor to ETR, phosphatidylinositol 3-kinase (PI3K) pathway hyperactivation can result from mutations to PIK3CA; ~40% of pts with HR+, HER2– ABC exhibit tumors with this mutation. Use of the oral α-specific PI3K inhibitor ALP + FUL significantly improved progression-free survival (PFS) in pts with a PIK3CA mutation (HR 0.65; 95% CI, 0.50-0.85; P<0.001) in SOLAR-1, which included both ET sensitive (ETS) and ETR pts (Table). ETS pts were later excluded by a protocol amendment. ETR was further defined as primary (1R) or secondary (2R) per ESMO criteria in both 1L and 2L pts. This subgroup analysis evaluated pts with a PIK3CA mutation based on tx line and endocrine status. Methods: SOLAR-1 was a phase 3, randomized, double-blind study of ALP 300 mg QD or PBO Q28d + FUL 500 mg Q28d + C1d15 in men and postmenopausal women with HR+, HER2– ABC whose disease progressed on/after an aromatase inhibitor. PFS was estimated by Kaplan-Meier method and median PFS (mPFS) presented by tx arm. A stratified Cox proportional hazards model estimated HR and 2-sided 95% CI. Results: Of 341 pts in the PIK3CA mutant cohort, 39 (11%) were ETS; 302 (89%) were ETR. mPFS in the ALP vs PBO arms was 22.1 vs 19.1 mo (HR 0.87; 95% CI, 0.35-2.17) for ETS pts and 9.4 vs 4.2 mo (HR 0.64; 95% CI, 0.48-0.84) for ETR pts. For ETR pts, mPFS for 1L (n=138) was 9.0 vs 4.7 mo (HR 0.69; 95% CI, 0.46-1.05) and for 2L (n=161) was 10.9 vs 3.7 mo (HR 0.61; 95% CI, 0.42-0.89). Conclusions: In SOLAR-1, mPFS was improved with ALP + FUL vs PBO + FUL across ETR pts in 1L and 2L. Representation of ETS pts was low in SOLAR-1, which included more ETR pts. Analysis of the PI3K pathway in ETS pts is warranted in future studies. Clinical trial information: NCT02437318. [Table: see text]

Patient-reported outcomes (PROs) in patients (pts) with PIK3CA-mutated hormone receptor-positive (HR+), human epidermal growth factor receptor-2–negative (HER2–) advanced breast cancer (ABC) from SOLAR-1

1039

Background: Approximately 40% of pts with HR+, HER2– ABC have tumors with a PIK3CA mutation, resulting in phosphatidylinositol 3-kinase (PI3K) pathway hyperactivation. Use of the oral α-specific PI3K inhibitor alpelisib (ALP) + fulvestrant (FUL) in SOLAR-1 significantly improved (vs placebo [PBO] + FUL) both progression-free survival (PFS) (median 11.0 vs 5.7 mo, respectively; HR 0.65; 95% CI, 0.50-0.85; P< 0.001) and objective response rate (ORR) (measurable disease: 36% vs 16%; P< 0.001) in the PIK3CA mutant cohort. In addition to primary efficacy and safety measures, PROs offer valuable insight into therapeutic benefit by measuring whether quality of life (QoL) is maintained during treatment. Methods: Postmenopausal women or men with HR+, HER2– ABC whose disease progressed on/after an aromatase inhibitor were randomized to receive ALP 300 mg once daily or PBO, + FUL 500 mg every 28 days + Cycle 1, Day 15. Secondary objectives included PROs using the EORTC QLQ-C30, EQ-5D-5L, and BPI-SF scales. PROs were collected at screening, every 8 wk for 18 mo then every 12 wk thereafter, at end of treatment, and during follow-up for efficacy. Linear mixed effects models were used to assess score changes from baseline. Time to 10% deterioration (TTD), an established measure of clinically meaningful change in QoL, was compared between the treatment arms’ survival distribution using Kaplan-Meier methodology. Results: At baseline, 93% of pts in the PIK3CA mutant cohort (n = 341) completed questionnaires; ≥75% completed them post-baseline. Adjusted mean changes from baseline in EORTC global health status/QoL scores were < 10% for all visits through wk 96 for both arms, with a mean difference between arms of < 3% for all visits. There was no difference between arms in TTD in global health/QoL status (HR 1.03; 95% CI, 0.72-1.48). Analysis of TTD in EORTC physical, social, and emotional functioning scores revealed no meaningful differences between arms. Conclusions: In addition to significantly improving PFS and ORR, overall QoL was maintained in pts treated with ALP + FUL. Clinical trial information: NCT02437318.

A peripheral nerve stimulator for nerve location controlled by the scrubbed anaesthetist

This newly designed peripheral nerve stimulator allows the scrubbed anaesthetist performing a nerve block to adjust the electrical current output needed for localisation of the target nerve without the need for an assistant.

Pump activated by a foot switch pedal for controlled administration of local anaesthetic drugs

We describe a newly designed syringe pump which is electrically controlled by a dual foot switch pedal. The device enables the scrubbed anaesthetist performing the regional block to aspirate, as well as to inject, the local anaesthetic without the need for any additional personnel.

A modified Guedel airway for continuous oxygenation and suctioning during fibreoptic bronchoscopy

We describe a modification to the Guedel airway that improves suction and oxygenation during fibreoptic bronchoscopy. The entire roof of a Guedel airway was removed. Two 2.5-mm internal diameter tracheal tubes were inserted into the modified airway to allow continuous oxygen delivery and suction throughout fibreoptic bronchoscopy. It was tested as a single-use device in ten patients undergoing awake fibreoptic bronchoscopy under sedation and topical anasthesia. During the procedure there were no problems with either fogging of the lens or secretions in the pharynx. In addition, oxyhaemoglobin saturation, as monitored continuously by pulse oximetry, was >/= 97% in all patients.