Effect of palbociclib plus endocrine therapy on time to chemotherapy across subgroups of patients with hormone receptor‒positive/human epidermal growth factor receptor 2‒negative advanced breast cancer: Post hoc analyses from PALOMA-2 and PALOMA-3

BACKGROUND

Previous analyses from the PALOMA-2 and PALOMA-3 studies showed that palbociclib (PAL) plus endocrine therapy (ET) prolongs time to first subsequent chemotherapy (TTC) versus placebo (PBO) plus ET in the overall population of patients with hormone receptor‒positive/human epidermal growth factor receptor 2‒negative (HR+/HER2-) advanced breast cancer (ABC). Here, we evaluated TTC in relevant patient subgroups.

METHODS

These post hoc analyses evaluated TTC by subgroup using data from 2 randomized, phase 3 studies of women with HR+/HER2- ABC. In PALOMA-2, postmenopausal patients previously untreated for ABC were randomized 2:1 to receive PAL (125 mg/day, 3/1-week schedule) plus letrozole (LET; 2.5 mg/day; n = 444) or PBO plus LET (n = 222). In PALOMA-3, premenopausal or postmenopausal patients whose disease had progressed after prior ET were randomized 2:1 to receive PAL (125 mg/day, 3/1-week schedule) plus fulvestrant (FUL; 500 mg; n = 347) or PBO plus FUL (n = 174).

RESULTS

First subsequent chemotherapy was received by 35.5% and 56.2% in PALOMA-2 and PALOMA-3 after progression on palbociclib plus ET or placebo plus ET. Across all subgroups analyzed, the median progression-free survival (PFS) was longer in the PAL plus ET arm than the PBO plus ET arm. TTC was longer with PAL plus ET versus PBO plus ET across the same patient subgroups in both studies.

CONCLUSIONS

Across all subgroups, PAL plus ET versus PBO plus ET had longer median PFS and resulted in prolonged TTC in both the PALOMA-2 and PALOMA-3 studies. Pfizer Inc (NCT01740427, NCT01942135).

ASTEFANIA: adjuvant ado-trastuzumab emtansine and atezolizumab for high-risk, HER2-positive breast cancer

There is a strong rationale for combining HER2-targeted therapies with cancer immunotherapy to increase efficacy in breast cancer, particularly in the early-stage setting, where the immune system has not been weakened by heavy pretreatment. ASTEFANIA aims to evaluate the efficacy of adjuvant atezolizumab in combination with ado-trastuzumab emtansine in patients with high-risk, HER2-positive early breast cancer and residual disease following HER2-based neoadjuvant therapy. Eligible patients will be randomized to receive ado-trastuzumab emtansine in combination with either atezolizumab or placebo for 14 cycles within 12 weeks of primary surgery. The primary outcome is invasive disease-free survival and secondary outcomes include additional efficacy end points, safety and pharmacokinetics. The study plans to enroll 1700 patients across 32 counties. Clinical Trial Registration: NCT04873362 (ClinicalTrials.gov).

Overall Survival with Palbociclib and Fulvestrant in Women with HR+/HER2- ABC: Updated Exploratory Analyses of PALOMA-3, a Double-blind, Phase III Randomized Study

PURPOSE

To conduct an updated exploratory analysis of overall survival (OS) with a longer median follow-up of 73.3 months and evaluate the prognostic value of molecular analysis by circulating tumor DNA (ctDNA).

PATIENTS AND METHODS

Patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced breast cancer (ABC) were randomized 2:1 to receive palbociclib (125 mg orally/day; 3/1 week schedule) and fulvestrant (500 mg intramuscularly) or placebo and fulvestrant. This OS analysis was performed when 75% of enrolled patients died (393 events in 521 randomized patients). ctDNA analysis was performed among patients who provided consent.

RESULTS

At the data cutoff (August 17, 2020), 258 and 135 deaths occurred in the palbociclib and placebo groups, respectively. The median OS [95% confidence interval (CI)] was 34.8 months (28.8-39.9) in the palbociclib group and 28.0 months (23.5-33.8) in the placebo group (stratified hazard ratio, 0.81; 95% CI, 0.65-0.99). The 6-year OS rate (95% CI) was 19.1% (14.9-23.7) and 12.9% (8.0-19.1) in the palbociclib and placebo groups, respectively. Favorable OS with palbociclib plus fulvestrant compared with placebo plus fulvestrant was observed in most subgroups, particularly in patients with endocrine-sensitive disease, no prior chemotherapy for ABC and low circulating tumor fraction and regardless of ESR1, PIK3CA, or TP53 mutation status. No new safety signals were identified.

CONCLUSIONS

The clinically meaningful improvement in OS associated with palbociclib plus fulvestrant was maintained with >6 years of follow-up in patients with HR+/HER2- ABC, supporting palbociclib plus fulvestrant as a standard of care in these patients.

Understanding the barriers to, and facilitators of, ovarian toxicity assessment in breast cancer clinical trials

BACKGROUND

Detailed toxicity data are routinely collected in breast cancer (BC) clinical trials. However, ovarian toxicity is infrequently assessed, despite the adverse impacts on fertility and long-term health from treatment-induced ovarian insufficiency.

OBJECTIVES

To determine the barriers to and facilitators of ovarian toxicity assessment in BC trials of anti-cancer drugs.

METHODS

Semi-structured interviews were conducted with purposively selected stakeholders from multiple countries involved in BC clinical trials (clinicians, consumers, pharmaceutical company representatives, members of drug-regulatory agencies). Participants were asked to describe the perceived benefits and barriers to evaluating ovarian toxicity. Interviews were transcribed verbatim, coded in NVivo software and analysed using inductive thematic analysis.

RESULTS

Saturation of the main themes was reached and the final sample size included 25 participants from 14 countries (9 clinicians, 7 consumers, 5 members of regulatory agencies, 4 pharmaceutical company representatives); half were female. The main reported barrier to ovarian toxicity assessment was that the issue was rarely considered. Reasons included that these data are less important than survival data and are not required for regulatory approval. Overall, most participants believed evaluating the impact of BC treatments on ovarian function is valuable. Suggested strategies to increase ovarian toxicity assessment were to include it in clinical trial design guidelines and stakeholder advocacy.

CONCLUSION

Lack of consideration about measuring ovarian toxicity in BC clinical trials that include premenopausal women suggest that guidelines and stronger advocacy from stakeholders, including regulators, would facilitate its more frequent inclusion in future trials, allowing women to make better informed treatment decisions.

Checkpoint inhibitor immunotherapy diminishes oocyte number and quality in mice

Loss of fertility is a major concern for female reproductive-age cancer survivors, since a common side-effect of conventional cytotoxic cancer therapies is permanent damage to the ovary. While immunotherapies are increasingly becoming a standard of care for many cancers-including in the curative setting-their impacts on ovarian function and fertility are unknown. We evaluated the effect of immune checkpoint inhibitors blocking programmed cell death protein ligand 1 and cytotoxic T lymphocyte-associated antigen 4 on the ovary using tumor-bearing and tumor-free mouse models. We find that immune checkpoint inhibition increases immune cell infiltration and tumor necrosis factor-α expression within the ovary, diminishes the ovarian follicular reserve and impairs the ability of oocytes to mature and ovulate. These data demonstrate that immune checkpoint inhibitors have the potential to impair both immediate and future fertility, and studies in women should be prioritized. Additionally, fertility preservation should be strongly considered for women receiving these immunotherapies, and preventative strategies should be investigated in future studies.

Pembrolizumab plus Chemotherapy in Advanced Triple-Negative Breast Cancer

BACKGROUND

In an interim analysis of this phase 3 trial, the addition of pembrolizumab to chemotherapy resulted in longer progression-free survival than chemotherapy alone among patients with advanced triple-negative breast cancer whose tumors expressed programmed death ligand 1 (PD-L1) with a combined positive score (CPS; the number of PD-L1-staining tumor cells, lymphocytes, and macrophages, divided by the total number of viable tumor cells, multiplied by 100) of 10 or more. The results of the final analysis of overall survival have not been reported.

METHODS

We randomly assigned patients with previously untreated locally recurrent inoperable or metastatic triple-negative breast cancer in a 2:1 ratio to receive pembrolizumab (200 mg) every 3 weeks plus the investigator's choice of chemotherapy (nanoparticle albumin-bound paclitaxel, paclitaxel, or gemcitabine-carboplatin) or placebo plus chemotherapy. The primary end points were progression-free survival (reported previously) and overall survival among patients whose tumors expressed PD-L1 with a CPS of 10 or more (the CPS-10 subgroup), among patients whose tumors expressed PD-L1 with a CPS of 1 or more (the CPS-1 subgroup), and in the intention-to-treat population. Safety was also assessed.

RESULTS

A total of 847 patients underwent randomization: 566 were assigned to the pembrolizumab-chemotherapy group, and 281 to the placebo-chemotherapy group. The median follow-up was 44.1 months. In the CPS-10 subgroup, the median overall survival was 23.0 months in the pembrolizumab-chemotherapy group and 16.1 months in the placebo-chemotherapy group (hazard ratio for death, 0.73; 95% confidence interval [CI], 0.55 to 0.95; two-sided P = 0.0185 [criterion for significance met]); in the CPS-1 subgroup, the median overall survival was 17.6 and 16.0 months in the two groups, respectively (hazard ratio, 0.86; 95% CI, 0.72 to 1.04; two-sided P = 0.1125 [not significant]); and in the intention-to-treat population, the median overall survival was 17.2 and 15.5 months, respectively (hazard ratio, 0.89; 95% CI, 0.76 to 1.05 [significance not tested]). Adverse events of grade 3, 4, or 5 that were related to the trial regimen occurred in 68.1% of the patients in the pembrolizumab-chemotherapy group and in 66.9% in the placebo-chemotherapy group, including death in 0.4% of the patients in the pembrolizumab-chemotherapy group and in no patients in the placebo-chemotherapy group.

CONCLUSIONS

Among patients with advanced triple-negative breast cancer whose tumors expressed PD-L1 with a CPS of 10 or more, the addition of pembrolizumab to chemotherapy resulted in significantly longer overall survival than chemotherapy alone. (Funded by Merck Sharp and Dohme; KEYNOTE-355 ClinicalTrials.gov number, NCT02819518.).

Alpelisib monotherapy for PI3K-altered, pre-treated advanced breast cancer: a phase 2 study

There is limited knowledge on the benefit of the α-subunit specific PI3K inhibitor alpelisib in later lines of therapy for advanced ER+HER2- and triple negative breast cancer (TNBC). We conducted a phase 2 multi-cohort study of alpelisib monotherapy in patients with advanced PI3K pathway mutant ER+HER2- and TNBC. In the intention to treat ER+ cohort, the overall response rate was 30% and the clinical benefit rate was 36%. Decline in PI3K pathway mutant ctDNA levels from baseline to week 8 while on therapy was significantly associated with a partial response, clinical benefit and improved progression free-survival (HR 0.24 95% CI 0.083 - 0.67, P = 0.0065). Detection of ESR1 mutations at baseline in plasma was also associated with clinical benefit and improved progression free survival (HR 0.22 95% CI 0.078 - 0.60, P = 0.003).

Integrating Immunotherapy Into the Treatment Landscape for Patients With Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is the most aggressive histologic subtype of breast cancer for which, until recently, treatment options have been limited to chemotherapy. In recent years, an improved understanding of the importance of tumor-infiltrating lymphocytes and the tumor microenvironment in TNBC has led to investigation of immune checkpoint inhibitors for treatment. There is now evidence from several randomized controlled trials that supports the addition of immune checkpoint inhibitors to first-line treatment of advanced TNBC and to neoadjuvant chemotherapy for stage II-III TNBC. In parallel, the PARP inhibitors have emerged as a targeted therapy option for patients with HER2-negative breast cancer harboring mutations in BRCA1, BRCA2, and PALB2. Here, we review the recent clinical trials that inform the integration of immune checkpoint inhibitors into treatments for TNBC and discuss ongoing challenges-including patient selection, management of resistance to post-checkpoint inhibitor therapy, and combining immunotherapy with targeted therapies, including PARP inhibitors.

Mechanisms of action and acquired resistance to atezolizumab plus nab-paclitaxel in metastatic triple-negative breast cancer (mTNBC)

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Background: In the IMpassion130 study (NCT02425891) first-line atezolizumab plus nab-paclitaxel (A+nP) provided clinical benefit compared with placebo plus nP (P+nP) in patients with mTNBC whose tumors were PD-L1+ (Schmid NEJM 2018). However, in many patients, disease that was initially controlled eventually progressed. The mechanism of action of A+nP and nP in the mTNBC tumor microenvironment (TME) and the biological changes associated with tumor progression with these therapies remain largely unknown. The goal of the current study was to evaluate biological changes in the TME induced by atezolizumab and nP early on treatment (OT) and at the time of progressive disease (PD) in IMpassion130. Methods: Paired tumor biopsies from IMpassion130 collected pre-treatment at baseline (BL), after 4 weeks OT, and at clinical PD were evaluated histologically for PD-L1 expression, CD8 content, stromal tumor infiltrating lymphocytes and immune phenotypes. RNA sequencing was also used to evaluate TNBC molecular subtypes and gene expression (hallmark gene sets, and immune cell and stromal gene signatures). Matched tumor pair samples from BL and PD were further analyzed by next-generation sequencing for genomic changes using the FoundationOne gene panel. Wilcoxon, Fisher, and McNemar’s tests were used for statistical analysis. Results: OT A+nP (n = 24 pairs), but not P+nP (n = 18 pairs) increased PD-L1 in both tumor-infiltrating immune cells and tumor cells, and increased frequency of immune-inflamed tumors. RNA-based signatures for A+nP showed an increase in lymphocytes (T-, B-, and NK cell), as well as IFN-α and IFN-γ responses, driven mainly by responders. While P+nP increased RNA-based stromal signatures (cancer-associated fibroblasts, pericytes, and angiogenesis) and epithelial mesenchymal transition, these changes were not observed with A+nP. OT A+nP and P+nP both reduced cell proliferation but only A+nP reduced metabolic pathways. At PD there was a significant reduction of RNA-based immune and stromal signatures in both A+nP (n = 59) and P+nP (n = 55) arms. Cell proliferation and DNA repair signatures were increased with A+nP but not P+nP. Evaluation of genomic changes suggested that both A+nP and P+nP increased tumor mutational burden (TMB), but only A+nP increased genomic scarring. At PD, the tumor immune phenotypes changed at PD with no directionality, while TNBC subtypes remained stable. Conclusions: A+nP boosted tumor immune inflammation and decreased tumor cell proliferation and metabolism in mTNBC patients, particularly in responders. Addition of atezolizumab prevented early stromal recruitment induced by nP. While decreased immune and stromal components and increased TMB were observed with both nP and A+nP, A+nP tumor escape was characterized by increased cell proliferation and DNA scarring. Clinical trial information: NCT02425891.

Dose-finding and -expansion studies of trastuzumab deruxtecan in combination with other anti-cancer agents in patients (pts) with advanced/metastatic HER2+ (DESTINY-Breast07 [DB-07]) and HER2-low (DESTINY-Breast08 [DB-08]) breast cancer (BC)

3025

Background: Trastuzumab deruxtecan (T-DXd), an antibody-drug conjugate composed of a humanized anti-HER2 monoclonal antibody and a topoisomerase I inhibitor payload, is approved for pts with unresectable or metastatic HER2+ BC with ≥2 prior anti-HER2–based therapies. T-DXd showed improved progression-free survival vs trastuzumab emtansine (T-DM1) as an earlier-line treatment (tx) for pts with HER2+ metastatic BC in the phase 3 DESTINY-Breast03 trial (Cortes J, et al. Ann Oncol. 2021;32:S1283-S1346. Abstract LBA1). Preliminary antitumor activity of T-DXd was shown in heavily pretreated pts with HER2-low advanced/metastatic BC in the phase 1 DS8201-A-J101 trial (Modi S, et al. J Clin Oncol. 2020;38:1887-1896). We report preliminary results from the dose-finding phase of 2 trials investigating T-DXd combination tx in HER2+ or HER2-low metastatic BC. Methods: DB-07 (phase 1b/2; NCT04538742) and DB-08 (phase 1b; NCT04556773) are 2-part, modular, open-label, multicenter trials of T-DXd combined with other anticancer tx in pts with advanced/metastatic BC that is HER2+ (DB-07) or HER2 low (DB-08). Part 1 of each study is an ongoing dose-finding phase; pts must have ≥1 prior tx for metastatic BC. Part 2 of each study is a dose-expansion phase; pts must have no (DB-07) or ≤1 (DB-08) prior tx for metastatic BC. We report preliminary results from the T-DXd + pertuzumab module of DB-07 part 1 (data cutoff: Oct 15, 2021) and T-DXd + anastrozole and T-DXd + fulvestrant modules of DB-08 part 1 (data cutoff: Sep 27, 2021); pts in the DB-08 modules must be hormone receptor positive. The part 1 primary objective was to assess safety and tolerability and determine the recommended phase 2 dose (RP2D) according to the modified toxicity probability interval-2 algorithm. Pts were followed up beyond the 21-day dose-limiting toxicity (DLT) period (28 days for T-DXd + fulvestrant) for safety events. Results: In DB-07, 7 pts were enrolled and received T-DXd 5.4 mg/kg + pertuzumab 420 mg (loading dose: 840 mg) every 3 wk (q3w; not evaluable for DLTs, n = 1). In DB-08, 6 pts were enrolled and received T-DXd 5.4 mg/kg q3w + anastrozole 1 mg daily (not evaluable for DLTs, n = 1); another 6 pts were enrolled and received T-DXd 5.4 mg/kg q3w + fulvestrant 500 mg every 4 wk (loading dose: 500 mg cycle 1 days 1 and 15). For all 3 modules, no DLTs were reported in any DLT-evaluable pts; the dose levels used in part 1 were approved to be the RP2Ds for use in the dose-expansion part of each corresponding module. No deaths on study or cases of interstitial lung disease/pneumonitis were reported to date. Conclusions: The RP2Ds for the T-DXd combinations were the standard doses for BC of each individual drug. These studies are ongoing, with additional T-DXd combinations being evaluated and further follow-up underway. Clinical trial information: NCT04538742; NCT04556773.

Targeting HER2 mutation–positive advanced biliary tract cancers with neratinib: Final results from the phase 2 SUMMIT basket trial

4079

Background: HER2 mutations are infrequent genomic events in biliary tract cancers (BTCs) and are associated with poor overall survival (OS) in patients with metastatic disease. HER2 overexpression is associated with an increased risk of disease recurrence in patients with resected BTC. There is limited data on targeting HER2 in BTC harboring activating somatic HER2 mutations. Neratinib, an irreversible, pan-HER, oral tyrosine kinase inhibitor, interferes with constitutive receptor kinase activation and has demonstrated activity in several HER2-mutant solid tumors. Methods: SUMMIT is an open-label, single-arm, multi-cohort, phase 2, ‘basket’ trial of neratinib in patients with solid tumors harboring oncogenic HER2 somatic mutations. The primary objective of the BTC cohort was to estimate objective response rate (ORR). Secondary objectives were clinical benefit rate (CBR), progression-free survival (PFS), OS, response duration, safety, and tolerability. Retrospective central confirmation of locally reported HER2 mutation (next-generation sequencing on archival or fresh tumor tissue using MSK-IMPACT or in cfDNA extracted from plasma by MSK-ACCESS) and association with outcome was an exploratory endpoint. This trial is registered with ClinicalTrials.gov (NCT01953926). Results: 25 treatment-refractory patients with metastatic BTC were enrolled (11 cholangiocarcinoma, 10 gallbladder, 4 ampullary cancers). ORR was 16% (95% CI 4.5–36.1%) and CBR was 28% (95% CI 12.1–49.4%). Median PFS and OS were 2.8 (95% CI 1.1–3.7) and 5.4 (95% CI 3.7–11.7) months, respectively. Median PFS for the gallbladder, cholangiocarcinoma and ampulla cohorts was 3.7 (95% CI 0.8–6.4), 1.4 (95% CI 0.5–9.1), and 1.1 (95% CI 1.1–3.8) months, respectively. Corresponding median OS values in these cohorts were 9.8 (95% CI 2.4–NE), 5.4 (95% CI 0.8–16.2), and 5.0 (95% CI 3.7–10.2) months, respectively. Central mutation confirmation was feasible for 23 of 25 patients; 22 were concordant with enrolment assays. The most common HER2 mutations were S310F (n = 11; 48%) and V777L (n = 4; 17%). Exploratory analyses suggested worse outcomes for HER2-mutant tumors with co-occurring oncogenic TP53 and CDKN2A alterations. Loss of amplified HER2 S310F and acquisition of multiple previously undetected oncogenic co-mutations were identified at progression in one of four responders. Diarrhea (56% any grade) was the most common toxicity. Conclusions: Neratinib is tolerable with modest antitumor activity in patients with BTC harboring HER2 mutations. Although the primary endpoint was met, future studies should evaluate rational combinations to augment and/or prolong responses. Clinical trial information: NCT01953926.

Neratinib plus fulvestrant plus trastzuzumab (N+F+T) for hormone receptor-positive (HR+), HER2-negative, HER2-mutant metastatic breast cancer (MBC): Outcomes and biomarker analysis from the SUMMIT trial

1028

Background: N is an oral, irreversible pan-HER TKI with activity against HER2 mutations. Genomic analyses from the SUMMIT MBC cohort following N±F suggest that resistance to N may occur via mutant allele amplification or secondary HER2 mutations. Adding T to N+F in SUMMIT showed encouraging durable responses in patients (pts) with HR+, HER2-mutant MBC and prior CDK4/6 inhibitors (CDK4/6i). Methods: SUMMIT (NCT01953926) enrolled pts with HR+, HER2-negative MBC with activating HER2 mutation(s) and prior CDK4/6i. Pts received N+F+T (oral N 240 mg/d with loperamide prophylaxis, im F 500 mg d1&15 of cycle 1 then q4w, iv T 8 mg/kg initially then 6 mg/kg q3w). During the small, randomized portion of the trial, pts received N+F+T, F+T or F (1:1:1 ratio). Pts randomized to F+T or F could crossover to N+F+T at progression. Efficacy endpoints: investigator-assessed ORR and CBR (RECIST v1.1); DOR; best overall response. Pre-treatment tumor tissue was centrally assessed retrospectively by next-generation sequencing. ctDNA from patient samples was assessed by NGS. Results: SUMMIT has completed enrolment; we report efficacy from 45 pts in the N+F+T cohort, plus 10 pts who progressed on F (n=6) or F+T (n=4) and crossed over to N+F+T (Table). HER2 allelic variants in the 45 N+F+T pts and ORR (%) (pts may have >1 mutation) were: V777L (n=6, 50%), L755S/P (n=15, 40%), S310F (n=4, 50%), exon 20 insertion (n=11, 36%), other KD missense (n=6, 33%), TMD missense (n=2, 0%), exon 19 deletion (n=1, 0%). Conclusions: N+F+T is a promising combination for HR+, HER2-mutated MBC with prior exposure to CDK4/6i, across a range of activating HER2 mutations. Results from the upcoming Apr 2022 data cut, including biomarkers, safety, mechanisms of acquired resistance, and preclinical mechanism of N+T, will be presented. Clinical trial information: NCT01953926. [Table: see text]

Historical early treatment effects of adjuvant endocrine therapy for breast cancer in high-risk subgroups: Reanalysis of BIG 1-98, SOFT and TEXT

508

Background: Clinical trials testing adjuvant endocrine therapy (ET) have not historically limited enrollment to patients with clinically high-risk breast cancer (BC), nor estimated treatment (trt) effects prior to 5 yrs. In light of recent trial results for adjuvant CDK4/6 inhibitors, we estimated early relative and absolute trt effects of aromatase inhibitor (AI) vs tamoxifen (T), with ovarian suppression (OFS) if premenopausal, in high risk subgroups. Methods: From pts enrolled in adjuvant phase 3 randomized clinical trials BIG 1-98 (postmenopausal, 5yr AI v T), TEXT (5yr AI+OFS v T+OFS) and SOFT (5yr AI+OFS v T+OFS v T), we identified subgroups with HR+/HER2- BC and high risk features (≥4 pLN; or 1-3 pLN with grade 3, pT≥5 cm and/or Ki-67≥20% [retrospectively centrally assessed]). TEXT randomized at start of adjuvant trt; BIG 1-98 and SOFT after chemotherapy. Disease-free survival (DFS) was defined from randomization to invasive recurrence at local, regional, distant or contralateral breast, second non-breast malignancy or death. We estimated trt effects as differences in 2, 3 and 5yr DFS Kaplan-Meier estimates (KM diffs at t yrs) and hazard ratios over time intervals of 0-2, 0-3 and 0-5 yrs (HRs over 0 to t yrs) to approximate the maturity of trial results with increasing follow-up. Results: The high-risk HR+/HER2- subgroups were 695/4922, 707/2660 and 526/3047 pts in BIG 1-98, TEXT and SOFT with 202, 122, 142 DFS events observed by 5 yrs since randomization. 60%, 46% and 44% of pts had ≥4 pLNs; 42%, 90% and 92% had chemotherapy. The table summarizes results. Conclusions: In re-analysis of clinical high risk HR+/HER2- subgroups of 3 trials each ̃700 pts, 5 yrs AI vs T had similar magnitude of early trt effects after 2-3 yrs follow-up of all pts vs trt effects observed after 27 mos median follow-up in monarchE trial (HR=0.70; KM diffs 2.7% at 2 yrs, 5.4% at 3 yrs; n=5637). Relative and absolute trt effects sometimes diminished when estimated over 5 yrs rather than over 2 yrs, but meaningful absolute differences remained at 5 yrs in contrast to Penelope-B trial results. Design and interpretation of high risk HR+/HER2- early BC trials may depend on timing of randomization and selection of backbone adjuvant trts; follow-up >5 yrs must remain standard. [Table: see text]

Diversity, inclusion, and patient (pt)-centricity in the randomized, double-blind, phase III ASTEFANIA study of ado-trastuzumab emtansine (T-DM1) ± atezolizumab in pts with HER2-positive early breast cancer (EBC) with residual invasive disease after preoperative chemotherapy and anti-HER2 therapy

e12504

Background: Representative pt populations in clinical trials are essential to address healthcare disparities between different racial/ethnic groups, including treatment access and pt outcomes. Many clinical trials mainly include White pts, which may limit the generalizability of the results to the global population. A framework that was recently developed by Genentech for improving inclusion of underrepresented pt groups, as well as the CHIMES (NCT04377555) and EMPACTA (NCT04372186) studies, have all shown the feasibility of inclusive studies. ASTEFANIA (NCT04873362) is a pt-centric study, which includes pt/investigator collaboration to keep a pt focus and tactics to recruit a diverse population and enable participation of underserved communities. We report early recruitment data. Methods: Global/local initiatives and inclusive eligibility criteria remove barriers to enrollment of underserved pts and support treatment journeys. Eligible pts (Eastern Cooperative Oncology Group performance status of 0/1; no prior immune checkpoint inhibitor treatment) are randomized 1:1 to T-DM1 (3.6 mg/kg) + atezolizumab (1200 mg)/placebo every 3 weeks for 14 cycles (stratification factors: clinical stage, hormone receptor status, preoperative anti-HER2 therapy, PD-L1 status). Primary endpoints: IDFS in intention-to-treat and PD-L1-positive populations. Secondary endpoints include overall survival, patient-reported outcomes (PROs), and safety. To remove pt access barriers and ease pt burden, consent and PRO forms are available in multiple languages, mobile nursing/telemedicine is planned for pts in rural areas, a wellness app and culturally sensitive support videos are being created, and financial support is provided for study-related expenses and loss of earnings. Results: Recruitment began in May 2021. By Feb 9, 2022, 236 pts were randomized: 147 White (62%), 72 Asian (31%; Indian [n = 4], Korean [46], Chinese [16], other [6]), 10 Hispanic (4%; 5 of whom also identify as American Indian), 2 Black (1%), and 5 pts (2%) whose race/ethnicity was unreported/unknown. Of these, 27 (11%) have received financial support. Enrollment in Africa begins later this year. Mobile nursing/telemedicine is planned for 14 countries. Conclusions: As the first study of its kind in HER2-positive EBC, ASTEFANIA actively aims to be accessible and include pts from a range of races/ethnicities and socially underserved backgrounds. There is a growing need for more compassionate and inclusive research. To do this, forward planning of pt-centric studies is essential to reduce the burden on study resources. We hope that the tactics outlined here will allow us to achieve our goals of inclusive research. Clinical trial information: NCT04873362.

Impact of steroid premedication on atezolizumab (atezo)-induced immune cell activation: A comparative analysis of IMpassion130 and IMpassion131 peripheral blood mononuclear cells (PBMCs)

1083

Background: The immune checkpoint inhibitor (ICI) atezo showed disparate outcomes as first-line therapy for metastatic TNBC when combined with nab-paclitaxel (nPac) in IMpassion130 [Schmid 2018] vs solvent-based paclitaxel (Pac) in IMpassion131 [Miles 2021]. A key difference between the trials was use of steroid premedication for Pac in IMpassion131 but not for nPac in IMpassion130. In patients (pts) receiving ICIs, prior steroid exposure has been linked to worse outcome [Drakaki 2020]. Further, IMpassion130 and IMpassion131 subgroup analyses suggested reduced atezo treatment effect in taxane-pretreated pts. This post hoc biomarker study explored the impact of: 1) steroids on systemic immune cell activation with atezo+taxane; 2) prior taxane exposure on atezo-induced immune cell activation. Methods: PBMCs collected at baseline and at day 1, cycle 2 (wk 4) were selected from matched pts (RECIST responders, PD-L1+, no liver metastases) from IMpassion130 and IMpassion131. Single-cell RNAseq was performed and the transcriptomic profile of immune cells was analyzed using GSEA pathway analyses, cell proportion and TCR clonality. Results: CITEseq from 695,851 single cells was generated from 39 IMpassion130 PBMC pairs (29 atezo+nPac; 10 placebo [Pla]+nPac) and 35 IMpassion131 pairs (26 atezo+Pac; 9 Pla+Pac). At wk 4, atezo+nPac resulted in increased IFNα and IFNγ responses across multiple cell types (CD4+ and CD8+ T cells, B cells, NK cells and monocytes) and proliferation in NK cells, but reduced TNF signaling across multiple cell types. In contrast, 4 wks of Pla+nPac increased TNF signaling but decreased IFNα and IFNγ responses. In the presence of steroids, 4 wks of atezo+Pac also increased IFNα and IFNγ responses mainly in NK cells and monocytes, but not T cells, and reduced proliferative pathways across B and T cells and TNF signaling. Pla+Pac increased TNF signaling only in NK cells, but reduced proliferative signatures across cell types. The only on-treatment change differing significantly between atezo+nPac vs atezo+Pac was the increase in proliferation pathways in NK, T and B cells with atezo+nPac. There were no significant changes in proportions of cell subsets or TCR clonality. PBMCs from taxane-pretreated pts had higher RNA-based metabolic profile (OxPhos, DNA repair and IFNα). Taxane-naive but not taxane-pretreated immune cells had increased IFNγ and IFNα response after atezo+taxane. Conclusions: Our results suggest that atezo+taxane promotes IFNα and IFNγ responses and that steroid co-administration reduces proliferation pathways across immune cells. Prior taxane exposure was associated with an increased metabolic status, possibly rendering immune cells less sensitive to atezo-induced activation. The immune context of taxane-naive TNBC may result in more potent immune activation with atezo. Clinical trial information: NCT02425891 and NCT03125902.

Neoadjuvant ipilimumab and nivolumab in combination with paclitaxel following anthracycline-based chemotherapy in patients with treatment resistant early-stage triple-negative breast cancer (TNBC): A single-arm phase 2 trial

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Background: We examined the efficacy and safety of neoadjuvant ipilimumab and nivolumab combined with paclitaxel following suboptimal response to anthracycline-based chemotherapy in patients with early-stage TNBC. Methods: This single arm multicentre phase 2 study enrolled 34 patients in 8 sites. Patients were aged ≥18 years with previously untreated stage 3 TNBC and were required to have ≥15mm of tumor remaining or 10mm of tumor with one positive lymph node after 4 cycles of anthracycline-based therapy. A suboptimal response subset at baseline was defined as < 50% reduction in tumor volume after initial anthracycline-based chemotherapy. Patients received neoadjuvant ipilimumab 1mg/kg IV 6 weekly for 2 doses and nivolumab 240mg every 2 weeks for 6 doses, with weekly paclitaxel at 80mg/m2 for 12 weeks, followed by surgery. Nivolumab (480mg 4-weekly) continued post operatively for further 9 months. Primary endpoint was pathological complete response (pCR) in breast and axilla, with secondary endpoints pCR in the suboptimal responders, pCR in PD-L1 positive patients (≥1% by SP142 assay), clinical response in the breast (ORR by RECIST), event-free (EFS) and overall survival (OS). Results: Between December 2018 and April 2020, 34 patients were enrolled, 33 were evaluable for the primary endpoint. Median age was 46.6yrs. At diagnosis, all patients were clinical stage III (AJCC v8), 16/34 (47%) were node positive, 8/31 (26%) were PD-L1 positive. At study entry (following anthracycline-based chemo), the median tumor size by ultrasound was 28mm (12-62). 16/33 (48%) were considered suboptimal responders. The pCR rate (ypT0ypN0) was 24.2% (95% CI, 11.09-42.26) in all evaluable, 37.5% [3/11] in PD-L1+ and 23% [5/22] in PD-L1- patients. In patients with suboptimal anthracycline response (< 50% tumor reduction), the pCR rate was 18.8% (95% CI, 8.52-75.51) (3/16). ORR in the breast was 57.6% (19/33) in all evaluable patients and 43.7% (8/20) in the suboptimal responders. The number of patients with residual cancer burden (RCB) class 0,1,2,3 was 8 (24%), 1 (3%), 19 (57.5%) and 5 (15%) respectively. With 14 months median follow up, 12-months EFS was estimated at 85% and OS 94%. For patients with pCR vs non-pCR, the hazard ratio (HR) for EFS was 0.62, 12 mo EFS was 100% vs 75%. In the neoadjuvant phase, 15/33 (45%) patients experienced at least one grade 3-4 adverse event. Most common immune-related event was grade 1 or 2 pneumonitis 9/33 (27%), which generally occurred with fever after the first dose of ipilimumab, and resolved. There was one case of grade 3 colitis. Conclusions: In these high risk patients, the addition of ipilimumab and nivolumab to neoadjuvant paclitaxel resulted in promising ORR and pCR rates, regardless of PD-L1 status. Rates of low grade pneumonitis were high. Follow up continues. Clinical trial information: ACTRN12617000651381.

What's in a name? That which we call Immune Cells by any other name would all smell as sweet

In the FUTURE-C-Plus phase 2 trial, patients with advanced previously untreated immune-enriched TNBC achieved an overall objective response rate of 81.3% with the combination of camrelizumab, famitinib and nab-paclitaxel. This supports that quantity of immune cells is important for identifying those with response to treatments combined with PD-1 targeting immunotherapy.

Prognostic Value of Stromal Tumor-Infiltrating Lymphocytes in Young, Node-Negative, Triple-Negative Breast Cancer Patients Who Did Not Receive (neo)Adjuvant Systemic Therapy

PURPOSE

Triple-negative breast cancer (TNBC) is considered aggressive, and therefore, virtually all young patients with TNBC receive (neo)adjuvant chemotherapy. Increased stromal tumor-infiltrating lymphocytes (sTILs) have been associated with a favorable prognosis in TNBC. However, whether this association holds for patients who are node-negative (N0), young (< 40 years), and chemotherapy-naïve, and thus can be used for chemotherapy de-escalation strategies, is unknown.

METHODS

We selected all patients with N0 TNBC diagnosed between 1989 and 2000 from a Dutch population–based registry. Patients were age < 40 years at diagnosis and had not received (neo)adjuvant systemic therapy, as was standard practice at the time. Formalin-fixed paraffin-embedded blocks were retrieved (PALGA: Dutch Pathology Registry), and a pathology review including sTILs was performed. Patients were categorized according to sTILs (< 30%, 30%-75%, and ≥ 75%). Multivariable Cox regression was performed for overall survival, with or without sTILs as a covariate. Cumulative incidence of distant metastasis or death was analyzed in a competing risk model, with second primary tumors as competing risk.

RESULTS

sTILs were scored for 441 patients. High sTILs (≥ 75%; 21%) translated into an excellent prognosis with a 15-year cumulative incidence of a distant metastasis or death of only 2.1% (95% CI, 0 to 5.0), whereas low sTILs (< 30%; 52%) had an unfavorable prognosis with a 15-year cumulative incidence of a distant metastasis or death of 38.4% (32.1 to 44.6). In addition, every 10% increment of sTILs decreased the risk of death by 19% (adjusted hazard ratio: 0.81; 95% CI, 0.76 to 0.87), which are an independent predictor adding prognostic information to standard clinicopathologic variables (χ² = 46.7, P < .001).

CONCLUSION

Chemotherapy-naïve, young patients with N0 TNBC with high sTILs (≥ 75%) have an excellent long-term prognosis. Therefore, sTILs should be considered for prospective clinical trials investigating (neo)adjuvant chemotherapy de-escalation strategies.

Young cancer patients with TNBC and high sTILs have an excellent outcome, even without systemic treatment

PTPN2 elicits cell autonomous and non-cell autonomous effects on antitumor immunity in triple-negative breast cancer

The tumor-suppressor PTPN2 is diminished in a subset of triple-negative breast cancers (TNBCs). Paradoxically, PTPN2-deficiency in tumors or T cells in mice can facilitate T cell recruitment and/or activation to promote antitumor immunity. Here, we explored the therapeutic potential of targeting PTPN2 in tumor cells and T cells. PTPN2-deficiency in TNBC associated with T cell infiltrates and PD-L1 expression, whereas low PTPN2 associated with improved survival. PTPN2 deletion in murine mammary epithelial cells TNBC models, did not promote tumorigenicity but increased STAT-1-dependent T cell recruitment and PD-L1 expression to repress tumor growth and enhance the efficacy of anti-PD-1. Furthermore, the combined deletion of PTPN2 in tumors and T cells facilitated T cell recruitment and activation and further repressed tumor growth or ablated tumors already predominated by exhausted T cells. Thus, PTPN2-targeting in tumors and/or T cells facilitates T cell recruitment and/or alleviates inhibitory constraints on T cells to combat TNBC.

Abstract GS2-05: Randomized comparison of adjuvant aromatase inhibitor exemestane (E) plus ovarian function suppression (OFS) vs tamoxifen (T) plus OFS in premenopausal women with hormone receptor-positive (HR+) early breast cancer (BC): update of the combined TEXT and SOFT trials

Background The updated combined SOFT+TEXT analysis, after 9 years median follow-up (MFU), revealed that adjuvant E+OFS vs T+OFS significantly improved disease-free survival (DFS) and distant recurrence-free interval (DRFI) but not overall survival (OS) in premenopausal women with HR+ early BC (Francis et al NEJM 2018). Given the high rate of OS in both arms and the long-term risk of relapse in HR+ BC, continued follow-up is key to assessing treatment benefit. We report a planned update analysis including OS with database lock of May 2021, after 13 years MFU.. Methods TEXT and SOFT enrolled premenopausal women with HR+ early BC from November 2003 to April 2011 (2660 in TEXT, 3047 in SOFT intention-to-treat (ITT) populations). TEXT randomized women within 12 weeks of surgery to 5 years E+OFS vs T+OFS; chemotherapy (CT) was optional and concurrent with OFS. SOFT randomized women to 5 years E+OFS vs T+OFS vs T alone, within 12 weeks of surgery if no CT planned, or within 8 months of completing (neo)adjuvant CT. Both trials were stratified by CT use. For the combined analysis of E+OFS vs T+OFS, the primary endpoint was DFS defined as invasive local, regional, distant recurrence, contralateral BC, second malignancy, death. Secondary endpoints included invasive breast cancer-free interval (BCFI), DRFI and OS.. Results: At database lock there were 953 DFS events and 473 deaths among 4690 pts assigned to T+OFS or E+OFS. In the ITT population, DFS, BCFI and DRFI outcomes for pts assigned E+OFS (n=2346) continued to be significantly improved over T+OFS (n=2344). 12-yr DFS was 80.5% vs. 75.9% (4.6% absolute improvement; HR 0.79 95% CI 0.70-0.90), 12-yr BCFI was improved by 4.1% and 12-yr DRFI by 1.8%. At 12 years OS was excellent in both groups, 90.1% in pts assigned E+OFS vs 89.1% in pts assigned T+OFS (HR 0.93; 95% CI, 0.78-1.11). There was heterogeneity of relative treatment effect according to HER2 status. When enrollment commenced, anti-HER2 adjuvant therapy was not standard; 53% of 583 pts with HER2+ tumors received HER2-targeted therapy. Below are Kaplan-Meier 12-yr estimates for patients with HER2 negative tumors by trial and chemotherapy stratum and for those with high-grade tumours, as an example of high-risk feature (Table). There is an emerging OS benefit for E+OFS vs T+OFS in pts with HER2 negative tumors who received chemotherapy in both trials.In pts with HER2-negative tumors, clinically-relevant outcome benefits were also seen in other high-risk subgroups: 12-yr DFS and OS were improved by 7.4% and 2.7%, respectively, in pts with pN1a disease, and by 10.6% and 4.5%, respectively, in those with tumors &gt;2cm.

Conclusions After 13 years MFU, adjuvant E+OFS, as compared with T+OFS, shows a sustained reduction in the risk of recurrence, more consistent in HER2 negative patients and in those with high-risk disease features, e.g., indication for adjuvant chemotherapy and G3 tumors. Oncologists may use this information to discuss potential benefits of E+OFS with individual patients. Follow-up continues for 5 additional years.

Chemotherapy HER2-negativeSOFTT+OFS (n=424)E+OFS (n=411)Absolute difference12-yr DFS67.4%74.1%6.7%12-yr OS81.1%84.4%3.3%TEXTT+OFS (n=656)E+OFS (n=661)Absolute difference12-yr DFS71.0%78.4%7.4%12-yr OS83.5%86.8%3.3%No chemotherapy HER2-negativeSOFTT+OFS (n=445)E+OFS (n=447)Absolute difference12-yr DFS82.9%88.2%5.3%12-yr OS96.1%96.9%0.9%TEXTT+OFS (n=499)E+OFS (n=492)Absolute difference12-yr DFS80.2%86.7%6.5%12-yr OS95.9%96.2%0.2%G3 HER2-negativeT+OFS (n=423)E+OFS (n=405)Absolute difference12-yr DFS62.7%73.0%10.3%12-yr OS78.1%83.6%5.5%

Citation Format: Meredith M Regan, Barbara A Walley, Gini F Fleming, Prudence A Francis, Marco A Colleoni, István Láng, Henry L Gómez, Carlo A Tondini, Harold J Burstein, Matthew P Goetz, Eva M Ciruelos, Vered Stearns, Hervé R Bonnefoi, Silvana Martino, Charles E Geyer, Jr, Claudio Chini, Alessandro M Minisini, Simon Spazzapan, Thomas Ruhstaller, Eric P Winer, Barbara Ruepp, Sherene Loi, Alan S Coates, Aron Goldhirsch, Richard D Gelber, Olivia Pagani. Randomized comparison of adjuvant aromatase inhibitor exemestane (E) plus ovarian function suppression (OFS) vs tamoxifen (T) plus OFS in premenopausal women with hormone receptor-positive (HR+) early breast cancer (BC): update of the combined TEXT and SOFT trials [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 GS2-05.

Abstract P1-18-14: Alpelisib monotherapy for PI3K-altered, pre-treated advanced breast cancer: A phase II study

Background: The PI3Kα subunit specific inhibitor alpelisib in combination with fulvestrant is approved in advanced breast cancer harbouring PIK3CA mutations, but predictive biomarkers are lacking. We performed a phase II single arm study of alpelisib monotherapy in previously treated advanced hormone receptor-positive HER2-negative (HR+HER2-) and triple negative breast cancer (TNBC) cohorts. Methods: Eligible patients with genomic aberrations in the PI3K pathway determined via tumour sequencing or ctDNA were given alpelisib 350mg oral daily as monotherapy. The primary endpoint was RECIST objective response rate (ORR) by central review. Secondary endpoints were clinical benefit rate (CBR), defined as complete or partial response or stable disease for ≥24 weeks, and progression free survival (PFS). Positron emission tomography (FDG-PET) was performed at baseline and 8 weeks. Efficacy was analysed according to baseline tumour alterations and serial ctDNA assays. Analyses were conducted separately for the HR+HER2- and TNBC cohorts. Stated p values are nominal without multiplicity adjustment. Results: 43 patients were recruited in total (33 in ER+HER2-, 10 in TNBC). Median follow-up was 44.6 months. In the TNBC cohort ORR and CBR were 0%, hence the cohort was stopped early. Data will be presented here for the HR+HER2- cohort. Of 33 ER+HER2- patients recruited, 28 (85%) were evaluable and 26 (79%) were evaluable for ORR after central review. PI3K pathway aberrations at study entry were mutations in PIK3CA (26/28; 93%) and PTEN (2/28; 7%). The median age was 60 (41 - 77yrs) and 27/28 of patients were female. 85.7% of cases had visceral disease, and 57% had &gt;3 metastatic sites. 100% of patients had received prior endocrine therapy and 78.6% prior chemotherapy, with a median of 3 prior lines (range 1 - 9). All patients were endocrine refractory. The ORR was 38% and CBR 43%. Median PFS was 4.6 months (95% CI, 3.7 - 7.3) and median OS 16.0 months (95% CI, 8.5 - 34.4). In patients with PET scans at baseline and 8 weeks, 67% (17/25) achieved a partial metabolic response but this was not associated with clinical benefit. In patients with partial response by RECIST, serial ctDNA levels at week 8 declined from baseline (p = 0.008) compared to patients with stable or progressive disease (p = 0.17), with similar results seen for patients with clinical benefit. Decline in ctDNA at week 8 was also associated with improved PFS (HR 0.24 [95% CI 0.08-0.67], p = 0.0065; 5.6 v 3.6 months). Multiple PIK3CA mutations were detected in plasma in 31% (8/26) of patients but had no impact on ORR/CBR. 39% (11/28) of patients had mutations in ESR1 detected in plasma at baseline, and this was associated with clinical benefit (p = 0.019) and improved PFS (HR=0.22 [95% CI 0.078-0.60], P=0.0032, 8.21 v 4.53 months). ctDNA assays detected 11 cases with ESR1 mutations compared to tumour sequencing which detected 5 cases only. No other baseline alterations were significantly associated with outcomes, although no patients (0/4) with PTEN alterations achieved clinical benefit. End of treatment ctDNA analysis identified multiple new alterations including MAP3K1 in 39% (11/28), TP53 in 32% (9/28) and PTEN in 25% (7/28). Adverse events included 20.9% grade ≥3 hyperglycaemia and 25.6% ≥grade 3 rash consistent with reported data. Permanent discontinuation of alpelisib for toxicity occurred in 15.2% (5/33) of patients. Conclusions: Alpelisib monotherapy in pre-treated ER+HER2- disease showed evidence of clinical efficacy. Decline in the levels of PIK3CA mutations detected with ctDNA on therapy are significantly associated with clinical benefit, as are the presence of ESR1 mutations at baseline. ctDNA improves the yield of ESR1 mutation detection and warrants further study as a biomarker of alpelisib monotherapy benefit in endocrine-refractory populations.

Citation Format: Peter Savas, Louisa Lisa Lo, Stephen James Luen, Elizabeth Fay Blackley, Courtney Templeton van Geelen, Yi-An Ko, Kate Moodie, Jason William Callahan, Chen-Fang Weng, Andjelija Zivanovic Bujak, Miriam Manning Yeung, Sarah Ftouni, Prudence Anne Francis, Sarah-Jane Dawson, Sherene Loi. Alpelisib monotherapy for PI3K-altered, pre-treated advanced breast cancer: A phase II study [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 P1-18-14.

Abstract ES6-3: Immunotherapy vs Capecitabine for Triple Negative Breast Cancer

Immunotherapy vs capecitabine for triple negative breast cancer. Educational session. Sherene Loi, MD, PhDPeter MacCallum Cancer Centre, Melbourne, Australia. Neoadjuvant treatment is now standard of care for the majority of early stage triple negative breast cancer (TNBC), with the achievement of non-pathological complete response (pCR) the main indicator to escalate treatment. Until recently only capecitabine was used in this setting. 2021 has seen reporting of the OlympiA adjuvant study, which reports major benefits for olaparib in germline BRCA positive TNBC patients, though a minority. KEYNOTE522 has now set the scene for incorporating neoadjuvant pembrolizumab with chemotherapy in early stage TNBC, with significantly improved event free survival, particularly those that do not achieve pCR. In this talk I will examine how we can rationally think about treating these patients with the available options.

Citation Format: S Loi. Immunotherapy vs Capecitabine for Triple Negative 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 ES6-3.

Abstract PD13-07: Activity and biomarker analyses from a phase Ia/b study of giredestrant (GDC-9545; G) with or without palbociclib (palbo) in patients with estrogen receptor-positive, HER2-negative locally advanced/metastatic breast cancer (ER+/HER2- LA/mBC)

Background A mainstay of ER+ BC treatment is to target ER activity and/or estrogen synthesis; however, during or after endocrine therapy (ET), many patients either relapse or develop resistance to such treatments due to several mechanisms, including ESR1 mutations which can be drivers of estrogen-independent transcription and proliferation. The majority of tumors remain dependent on ER signaling, and it is possible that patients will be responsive to second- or third-line ET after they have progressed on previous therapies. The highly potent, nonsteroidal oral selective ER antagonist and degrader G achieves robust ER occupancy and is active in patients with either ESR1-wildtype or -mutant tumors and in patients who had previously been treated with ET. G was well tolerated as a single agent and in combination with palbo, with antitumor activity shown in the nonrandomized, open-label, dose-escalation and -expansion, phase Ia/b GO39932 study (NCT03332797). We present updated activity and biomarker analyses in patients treated with 30 mg G monotherapy and those treated with 100 mg G + 125 mg palbo ± luteinizing hormone-releasing hormone (LHRH) agonists (clinical cutoff: Apr 16, 2021); 30 mg has since been selected as the dose in both the single agent and combination settings. Methods Eligible patients had ≤2 prior therapies for LA/mBC, disease recurrence, or progression while on adjuvant ET for ≥24 months and/or ET for LA/mBC, and tumor response or stable disease ≥6 months. All were postmenopausal (premenopausal women were allowed co-administered LHRH agonists with 100 mg G). Oral G was given daily on Days (D)1-28 of each 28-day cycle (C); 125 mg palbo, on a 21-day on/7-day off schedule. Modulation of ER signaling and proliferation of paired pre- and on-treatment (C2D8) tumor biopsies were assessed with immunohistochemistry for ER, progesterone receptor (PgR), and the proliferation marker Ki67, as well as with gene expression analysis of a predefined set of 38 ER target genes using the Illumina TruSeq RNA Access method. Plasma samples collected pre- and on-treatment (C1D15 and/or C2D1) were assessed for circulating tumor (ct)DNA using a digital PCR BEAMing assay detecting a total of 22 mutations across ESR1, AKT1, and PIK3CA. Results Objective response rates in patients with measurable disease at baseline were 20.0% in the 30 mg G group (6/30 patients) and 47.7% in the 100 mg G + palbo ± LHRH (combination) group (21/44). Clinical benefit rates were 55.0% (22/40 patients) and 81.3% (39/48), respectively. Overall, 21 pre- and on-treatment-paired tumor biopsies were collected in the 30 mg (n=13) and combination (n=8) groups. Consistent downregulation of ER, PgR, Ki67, and ER pathway activity was observed at C2D8, regardless of clinical benefit or baseline ESR1 mutation, demonstrating consistent on-target activity of G. Stronger Ki67, ER, and PgR suppression was seen with the addition of palbo to G. Of the 36 patients across both cohorts with a detectable ctDNA baseline ESR1 mutation, 16 had &gt;1 baseline ESR1 mutation. Of the eight unique ESR1 mutations detected, none showed an association with response. At C2D1, 34 patients had a decrease in ESR1 ctDNA levels from baseline, of which 27 became undetectable for ESR1 ctDNA. Early changes in PIK3CA and AKT1 ctDNA levels, but not ESR1, trended with response. Conclusions Encouraging clinical activity was observed with single agent G at 30 mg and with G at 100 mg in combination with palbo. Biomarker analyses demonstrated consistent biologic activity of G, and largely consistent decreases of ESR1 ctDNA levels. Further updated activity and biomarker data, including PAM50 subtype classifications, will be presented.

Citation Format: Nicolas C Turner, Sherene Loi, Heather M Moore, Ching-Wei Chang, Jennifer Eng-Wong, Aditya Bardia, Valentina Boni, Joohyuk Sohn, Komal L Jhaveri, Elgene Lim. Activity and biomarker analyses from a phase Ia/b study of giredestrant (GDC-9545; G) with or without palbociclib (palbo) in patients with estrogen receptor-positive, HER2-negative locally advanced/metastatic breast cancer (ER+/HER2- LA/mBC) [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 PD13-07.

Abstract P5-19-03: What are the barriers to assessment of ovarian toxicity in breast cancer clinical trials?

Background Toxicity data are routinely collected in phase 3 (neo)adjuvant breast cancer (BC) clinical trials, but ovarian toxicity is infrequently assessed, despite its impact on fertility and long-term health. Thus, little is known about the ovarian effects of newer BC therapies. This results in an information gap for women when making treatment decisions. We explored the barriers to collecting ovarian toxicity data and/or including ovarian function as an endpoint in BC trials of anti-cancer drugs. Methods Semi structured interviews were conducted with key stakeholders involved in BC clinical trials (clinicians, consumers, pharmaceutical companies, drug regulatory advisors). Participants were asked detailed questions about how trial endpoints are selected, whether effects on the ovary are assessed, and barriers to and benefits of collecting ovarian function data to assess ovarian toxicity. Interviews were transcribed verbatim, coded in NVivo software and analysed using inductive thematic analysis. Results Saturation was reached after 25 interviews (9 clinicians, 7 consumers, 5 drug regulatory advisors, 4 pharmaceutical company advisors); half were female. Participants were from North America (20%), Europe (52%), Australia (24%), Asia (4%). Median age was 50 years and median time in breast cancer research or drug regulation was 16 years. The main reported barrier to the collection of ovarian toxicity data in clinical trials was that this issue was rarely considered. Reasons included that these data are considered less important than survival data and are not required for regulatory approval. Other barriers included limited resources, lack of knowledge regarding how to assess ovarian side effects and lack of relevance in certain settings (further detail in Table 1). Most participants believed assessing ovarian toxicity in trials would be beneficial to clinicians and to patients (eg. assisting treatment and family planning decisions). Strategies to increase ovarian toxicity assessment included its inclusion in clinical trial design guidelines, improving familiarity with ovarian function markers among trial design decision makers, and increased stakeholder interest. A stronger consumer voice and regulatory and clinician advocacy were regarded as important. Regarding trial endpoint selection, pharmaceutical companies were almost always identified as the main decision maker, but clinicians including cooperative trial group researchers, consumers, regulators, and statisticians were also important contributors. While most consumers and pharmaceutical company advisors felt clinicians and consumers influenced trial design, in contrast, some clinicians and regulators reported consumers and clinicians had little influence. Factors identified as important considerations in determining trial endpoints included the main goal of the trial (eg. regulatory approval), established standardised endpoints, resources, and the investigational agent studied. All pharmaceutical advisors reported that meeting the requirements for regulatory approval was the major factor considered during endpoint selection. Conclusion This qualitative analysis evaluates the barriers to including measures of ovarian function in BC clinical trials. Increased awareness, stronger advocacy and guidelines might lead to more frequent inclusion of this important endpoint in future trials that include premenopausal women with early BC.

Table 1.Emergent themes regarding ovarian toxicity assessment in BC trialsThemeDomainCategory 1: Barriers to assessment of ovarian function Not prioritisedNot discussed or thought about;Not the primary question studied by clinical trial;Less important than other endpoints/data;Not required for regulatory approval;Data not related to survival is infrequently published;More appropriate for a follow up/registry studyToo resource intensive A burden on investigators and patients;Difficult to collect good quality data;Assessment not considered feasible;Time to obtaining results too long;Too costlyLack of knowledgeLack of clinician knowledge regarding ovarian function side effects;Lack of consensus regarding which markers to assess;Lack of preclinical data suggestive of ovarian toxicityData not relevant in certain settingsConcurrent use of gonadotoxic chemotherapy;Trials mandate contraception use;Want to suppress ovarian function in some breast cancer phenotypes;Low numbers of premenopausal women enrolled;Investigational agent already known to cause ovarian toxicity/suppressionCategory 2: Perceived benefits of assessing ovarian function Data important to patientsImproved ability to make informed cancer treatment decisions;Improved ability to make fertility and ovarian preservation decisions;Infertility and early menopause are relevant and important to patients;Preservation of ovarian function is important for quality of life;To avoid potential harm to patientsData important to cliniciansImproved ability to counsel patients;Improved understanding of the investigational agent;Improved understanding of the impact of ovarian function on disease outcomes;Holistic understanding of a patient’s experience on treatment;Prospective information is more robust than retrospective dataCategory 3: Strategies to improve inclusionIncreased stakeholder interestIncreased clinician advocacy;Increased consumer voice;Increased regulatory buy in;Increased cooperative trial group interest;Increased reproductive specialist involvement;Increased pharmaceutical company interestIncreased awareness regarding ovarian function and onco-fertilityTrial design guidelines and recommendations;Increased discussion and education;Improved familiarity with ovarian markers and ease of incorporation/collection;Use of social media and internet resources

Citation Format: Wanyuan Cui, Kelly-Anne Phillips, Prudence A Francis, Sherene Loi, Richard A Anderson, Ann H Partridge, Louise A Keogh. What are the barriers to assessment of ovarian toxicity in breast cancer clinical trials? [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 P5-19-03.

Abstract PD10-04: Phase Ib/II open-label, randomized trial of atezolizumab (atezo) with ipatasertib (ipat) and fulvestrant (fulv) vs control in MORPHEUS-HR+ breast cancer (M-HR+ BC) and atezo with ipat vs control in MORPHEUS triple negative breast cancer (M-TNBC)

Background: The MORPHEUS platform consists of multiple, global, open-label, randomized Phase Ib/II trials designed to gauge safety and identify early efficacy signals in treatment (tx) combinations across cancers. Within MORPHEUS, atezo (anti-PD-L1) was evaluated with ipat, an oral AKT inhibitor, with (M-HR+ BC) and without (M-TNBC) fulv. Methods: In 2 separate randomized trials, eligible immune checkpoint inhibitor naive pts with either 2L/3L HR+ chemotherapy-naive BC who had prior CDK4/6 inhibitor treatment or 2L TNBC, received atezo (840 mg D1, 15) with ipat (400 mg D1-21); pts with HR+ BC also received fulv monthly. Control tx for M-HR+ BC (NCT03280563) was fulv and for M-TNBC (NCT03424005) was capecitabine; given the adaptive nature of the MORPHEUS platform only some of the control arm pts were enrolled concurrently with pts in the ipat arms for M-HR+ BC. Primary endpoints were ORR (overall response rate; investigator-assessed RECIST 1.1) and safety. Progression-free survival (PFS) and overall survival (OS) were secondary endpoints. Results: Median duration of survival follow-up was 7.6 months for M-HR+ BC (data cutoff: Aug 2020) and 10.8 for M-TNBC (data cutoff: Mar 2021). In M-HR+ BC, none of whom received prior fulvestrant, 26 pts received atezo + ipat + fulv and 15 received fulv. Confirmed ORRs were 23.1% (95% CI: 9.0, 43.7) and 0% (95% CI: 0, 21.8), respectively. Median PFS was 4.4 mo (95% CI: 1.6, not evaluable) and 1.9 mo (95% CI: 1.6, 3.9), respectively. Updated survival data will be presented. Respectively, 61.5% and 20.0% of pts had Gr 3-4 AEs; no G5 AEs were observed; serious AEs (SAEs) occurred in 38.5% and 13.3% of pts; 7.7% and 0% of pts had tx-related AEs leading to tx withdrawal. The most common tx-related AEs were rash (73.0%), diarrhea (53.8%), nausea (42.3%), fatigue (26.9%), vomiting (23.1%), decreased appetite (19.2%), headache (15.4%), pyrexia (11.5%), hyperglycemia (11.5%), and aspartate aminotransferase (AST) increase (11.5%), in the combination arm; of these, rash (38.4%), diarrhea (7.7%), and AST increase (7.7%) included Grade 3-4 tx-related AEs. In M-TNBC, 29 pts received atezo + ipat and 24 received capecitabine. Confirmed ORRs were 3.4% (95% CI: 0.1, 17.8) and 20.8% (95% CI: 7.1, 42.2), respectively. Median PFS was 1.7 mo (95% CI: 1.5, 2.8) and 4.1 mo (95% CI: 2.3, 5.7), respectively. Median OS was 10.8 mo (95% CI: 7.0, 18.1) and 15.2 mo (95% CI: 14.4, 20.8). Gr 3-4 AEs were seen in 51.7% and 37.5% of pts, respectively; Gr 5 AEs were seen in 1 pt in the combination arm (encephalitis due to atezo). SAEs occurred in 51.7% and 16.7% of pts, respectively; 6.9% and 4.2% of pts had tx-related AEs leading to tx withdrawal. The most common tx-related AEs were rash (55.2%), diarrhea (48.3%), nausea (37.9%), pyrexia (31.0%), and fatigue (24.1%) in the combination arm; of these, rash (24.1%), fatigue (3.4%), and pyrexia (3.4%) included Gr 3-4 tx-related AEs. Biomarker data, including PI3K pathway status, PD-L1 and CD8-panCK expression, will also be presented. Conclusion: Atezo + ipat + fulv was tolerable with a preliminary efficacy signal in HR+ BC. Atezo + ipat had limited efficacy in biomarker unselected TNBC.

Citation Format: Sara A. Hurvitz, Valentina Boni, Elizabeth Comen, Seock-Ah Im, Kyung Hae Jung, Sung-Bae Kim, Keun Seok Lee, Sherene Loi, Hope S. Rugo, Amir Sonnenblick, Melinda L. Telli, Kelly DuPree, Marcella Fasso, Ya-Chen Lin, Mina Nikanjam, Frauke Schimmoller, Xiaosong Zhang, Jing Zhu, Peter Schmid. Phase Ib/II open-label, randomized trial of atezolizumab (atezo) with ipatasertib (ipat) and fulvestrant (fulv) vs control in MORPHEUS-HR+ breast cancer (M-HR+ BC) and atezo with ipat vs control in MORPHEUS triple negative breast cancer (M-TNBC) [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 PD10-04.

Abstract PD4-04: Updated results of tucatinib vs placebo added to trastuzumab and capecitabine for patients with previously treated HER2-positive metastatic breast cancer with brain metastases (HER2CLIMB)

Background: Tucatinib is an oral tyrosine kinase inhibitor highly specific for HER2 that is approved for use in combination with trastuzumab and capecitabine in adults with advanced or metastatic HER2+ breast cancer, including patients with brain metastases, who have received one or more prior anti-HER2-based regimens in the metastatic setting. In the HER2CLIMB trial, the tucatinib regimen significantly prolonged progression-free survival (PFS) and overall survival (OS) in patients with HER2+ metastatic breast cancer (Murthy, NEJM 2020), including in patients with untreated, treated stable, and treated progressing brain metastases (Lin, J Clin Oncol, 2020). With an additional 15.6 months of follow-up, addition of tucatinib continued to show clinically meaningful prolongation of PFS and OS in the total study population (Curigliano, ASCO Meeting, 2021). We report updated results of exploratory efficacy analyses in patients with brain metastases. Methods: All patients in HER2CLIMB had a baseline brain MRI. Patients with brain metastases were eligible and classified as untreated, treated stable, or treated progressing. Patients were randomized 2:1 to receive tucatinib 300 mg twice daily or placebo, in combination with trastuzumab and capecitabine. Following the primary analysis, the protocol was amended to unblind sites to treatment assignment and allowed crossover from the placebo regimen to the tucatinib regimen. Efficacy analyses in patients with brain metastases at baseline were performed at approximately 2 years from the last patient randomized by applying RECIST 1.1 to the brain based on investigator evaluation. OS and CNS-PFS (progression in the brain or death) were evaluated in all patients with brain metastases. Patients without CNS-PFS events were censored at the last brain MRI. Confirmed intracranial (IC) objective response rate (ORR-IC) was evaluated in patients with measurable IC disease. Results: At a median follow-up of 29.6 months, median OS was 21.6 months vs 12.5 months in all patients with brain metastases (HR: 0.60; 95% CI: 0.44, 0.81), 21.4 months vs 11.8 months in patients with untreated/treated progressing brain metastases (HR: 0.52; 95% CI: 0.36, 0.77), and 21.6 months vs 16.4 months in patients with treated stable brain metastases (HR: 0.70; 95% CI: 0.42, 1.16). Median CNS-PFS was 9.9 months vs 4.2 months in all patients with brain metastases (HR: 0.39; 95% CI: 0.27, 0.56), 9.6 months vs 4.0 months in patients with untreated/treated progressing brain metastases (HR: 0.34; 95% CI: 0.22, 0.54), and 13.9 months vs 5.6 months in patients with treated stable brain metastases (HR: 0.41; 95% CI: 0.19, 0.85). ORR-IC was higher in the tucatinib arm (47.3%; 95% CI: 33.7, 61.2) vs the placebo arm (20.0%; 95% CI: 5.7, 43.7) for patients with brain metastases, and median duration of response (DOR) was 8.6 months (95% CI: 5.5, 10.3) vs 3.0 months (95% CI: 3.0, 10.3). Conclusions: With 15.6 months of additional follow-up, the tucatinib-trastuzumab-capecitabine regimen resulted in a robust and durable prolongation of OS for all patients with HER2+ metastatic breast cancer and brain metastases. Additionally, this benefit was maintained in patients with untreated/treated progressing and treated stable brain metastases. Treatment with tucatinib continued to show clinically meaningful benefit in CNS-PFS consistent with the primary analysis.

Citation Format: Nancy U Lin, Rashmi K Murthy, Vandana Abramson, Carey Anders, Thomas Bachelot, Philippe Bedard, Virginia Borges, David Cameron, David Cameron, Lisa Carey, A Jo Chien, Giuseppe Curigliano, Michael DiGiovanna, Karen Gelmon, Gabriel Hortobagyi, Sara Hurvitz, Ian Krop, Sherene Loi, Sibylle Loibl, Volkmar Mueller, Mafalda Oliveira, Elisavet Paplomata, Mark Pegram, Dennis Slamon, Amelia Zelnak, Jorge Ramos, Wentao Feng, Eric Winer. Updated results of tucatinib vs placebo added to trastuzumab and capecitabine for patients with previously treated HER2-positive metastatic breast cancer with brain metastases (HER2CLIMB) [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 PD4-04.

Abstract OT2-11-09: Lidera breast cancer: A phase III adjuvant study of giredestrant (GDC-9545) vs physician’s choice of endocrine therapy (ET) in patients (pts) with estrogen receptor-positive, HER2-negative early breast cancer (ER+/HER2- EBC)

BACKGROUND ETs that target ER activity and/or estrogen synthesis are the mainstay of ER+ BC treatment. Despite best management, up to 20% of pts with ER+/HER2- eBC develop resistance (in some cases due to the acquisition of tumor mutations in ESR1 that can drive estrogen-independent transcription and proliferation) and still have high recurrence rates on standard ETs. New treatment alternatives for ER+/HER2- eBC are needed to reduce risk of recurrence and improve survival, tolerability, quality of life, and adherence. Giredestrant is a highly potent, nonsteroidal oral selective ER antagonist and degrader (SERD). It achieves robust ER occupancy and is active against tumors that retain ER-sensitivity or have ESR1 mutation(s). Giredestrant has been demonstrated to be more potent in vitro and achieves higher ER occupancy in vivo than fulvestrant, the only currently approved SERD. Early phase clinical studies have demonstrated that single-agent giredestrant (30 mg daily) has promising clinical and pharmacodynamic activity, and is well-tolerated in the ER+/HER2- eBC and metastatic BC settings. TRIAL DESIGN This is a phase III, global, randomized, open-label, multicenter study evaluating the efficacy and safety of adjuvant giredestrant vs physician’s choice of adjuvant ET in pts with medium- and high-risk stage I-III histologically confirmed ER+/HER2- eBC. Pts are randomized 1:1 to oral 30 mg daily giredestrant or physician’s choice of standard ET (tamoxifen, anastrozole, letrozole, or exemestane, given according to prescribing information). Stratification factors are risk (medium vs high, based on anatomic [tumor size, nodal status] and biologic features [grade, Ki67, gene signatures if available]); geographic region (US/Canada/Western Europe vs Asia-Pacific vs rest of the world); prior chemotherapy (no vs yes); and menopausal status (pre-/perimenopausal vs postmenopausal). Beginning on Day 1 of Cycle 1, pts will be treated with giredestrant or physician’s choice of standard ET for at least 5 years. Continuing physician’s choice of standard ET after 5 years is at discretion of the investigator and per local standard of care. ELIGIBILITY Female/male pts with medium-/high-risk stage I-III ER+/HER2- eBC; prior curative surgery; completion of (neo)adjuvant chemotherapy (if administered) and/or surgery &lt;12 months prior to enrolment; no prior ET (up to 4 weeks of [neo]adjuvant ET is allowed). For men and pre-/perimenopausal women, a luteinizing hormone-releasing hormone agonist will be given per local prescribing information (mandatory for pts in the giredestrant arm). AIMS Primary endpoint: Invasive disease-free survival (IDFS). Secondary endpoints: Overall survival; IDFS (STEEP definition, including second non-primary BC); disease-free survival; distant recurrence-free survival; locoregional recurrence-free interval; safety; pharmacokinetics; pt-reported outcomes. In addition, this study aims to improve health equity in research and expand clinical trial access. The study will also use/develop digital healthcare solutions, which will enable better understanding of patients’ needs and their adherence to ET. STATISTICAL METHODS The primary endpoint analysis will use a stratified log-rank test at an overall 0.05 significance level (two-sided). An interim analysis and a futility analysis are planned, and an independent data monitoring committee will be in place. ACCRUAL Target enrollment is 4100 pts globally once the study is open for enrollment. CONTACT INFORMATION For more information or to refer a patient, email global.rochegenentechtrials@roche.com or call 1-888-662-6728 (USA only). Clinicaltrials.gov number NCT04961996.

Citation Format: Aditya Bardia, Peter Schmid, Nadia Harbeck, Mothaffar F Rimawi, Sara A Hurvitz, Sherene Loi, Shigehira Saji, Kyung Hae Jung, Gustavo Werutsky, Daniil Stroyakovskii, Vanesa López-Valverde, David Tesarowski, Chenglin Ye, Michael Davis, Tanja Badovinac Crnjevic, Pablo Diego Perez-Moreno, Charles E Geyer, Jr. Lidera breast cancer: A phase III adjuvant study of giredestrant (GDC-9545) vs physician’s choice of endocrine therapy (ET) in patients (pts) with estrogen receptor-positive, HER2-negative early breast cancer (ER+/HER2- EBC) [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 OT2-11-09.

Abstract GS1-02: Final results of KEYNOTE-355: Randomized, double-blind, phase 3 study of pembrolizumab + chemotherapy vs placebo + chemotherapy for previously untreated locally recurrent inoperable or metastatic triple-negative breast cancer

Background: In the phase 3 KEYNOTE-355 trial (NCT02819518), pembrolizumab (pembro) combined with chemotherapy (chemo) showed statistically significant improvements in OS and PFS compared to placebo + chemo in patients with previously untreated locally recurrent inoperable or metastatic TNBC whose tumors expressed PD-L1 with a combined positive score (CPS) ≥10. There were no statistically significant differences between treatment groups in the CPS ≥1 population, and statistical significance was not tested in the ITT population due to the prespecified testing strategy. Here, we compare outcomes in subgroups of patients by additional CPS cut-offs to the primary results of KEYNOTE-355. Methods: 847 patients with measurable disease per RECIST v1.1, ECOG PS 0-1, and ≥6 month disease-free interval were randomized 2:1 to pembro + chemo (nab-paclitaxel 100 mg/m2 days 1, 8, and 15 every 28 days; paclitaxel 90 mg/m2 days 1, 8, and 15 every 28 days; or gemcitabine 1000 mg/m2 + carboplatin AUC 2 days 1 and 8 every 21 days) or placebo + chemo for up to 35 administrations of pembro/placebo or until progression/intolerable toxicity. Patients were stratified by chemo type (taxane or gemcitabine-carboplatin), PD-L1 status (CPS ≥1 or &lt;1), and prior neoadjuvant/adjuvant treatment with same-class chemo (yes or no). Dual primary endpoints were OS and PFS (RECIST v1.1, blinded independent central review) in patients with PD-L1-positive tumors (CPS ≥10 and ≥1) and in the ITT population. Hazard ratios (HRs) and 95% CIs in the additional CPS subgroups were based on an unstratified Cox model. Results: At the time of the final analysis (data cutoff, June 15, 2021), the median time from randomization to data cutoff was 44 months. Baseline characteristics of the CPS 1-9, 10-19, and ≥20 subgroups were generally similar to those of the ITT population. In the primary analyses, the HRs (95% CI) for OS were 0.73 (0.55-0.95) in the CPS ≥10 subgroup, 0.86 (0.72-1.04) in the CPS ≥1 subgroup, and 0.89 (0.76-1.05) in the ITT population; HRs (95% CI) for PFS were 0.66 (0.50-0.88), 0.75 (0.62-0.91), and 0.82 (0.70-0.98), respectively. Efficacy data are presented for the additional CPS subgroups in the Table. For OS, results in the CPS 1-9 subgroup showed comparable efficacy for pembro + chemo and placebo + chemo; however, results in the CPS 10-19 and CPS ≥20 subgroups showed a similar treatment benefit with the addition of pembro. Results for PFS were generally consistent with those observed for OS.

Conclusions: These results provide support that CPS ≥10 is a reasonable cut-off to define the population of patients with metastatic TNBC expected to derive treatment benefit from pembro + chemo.

Table. Efficacy in additional subgroups of patients by PD-L1 CPSCPS subgroupTreatmentMedian OS, mo (95% CI)OS HR (95% CI)*Median PFS, mo (95% CI)PFS HR (95% CI)*1-9†Pembro + Chemo. n = 20513.9. (12.2-16.6)1.09 (0.85-1.40)5.7. (5.4-7.4)0.85 (0.65-1.11)Placebo + Chemo n = 10815.5. (12.4-17.6)5.6. (5.3-7.6)10-19†Pembro + Chemo. n = 8020.3. (15.2-29.0)0.71 (0.46-1.09)9.9. (7.4-11.8)0.70 (0.44-1.09)Placebo + Chemo n = 3917.6. (10.3-25.8)7.6. (5.3-9.7)≥20‡Pembro + Chemo. n = 14024.0 (19.0-28.3)0.72 (0.51-1.01)9.2 (7.6-11.8)0.62 (0.44-0.88)Placebo + Chemo n = 6415.6. (12.3-20.8)5.4 (3.9-7.2)*Analyses based on an unstratified Cox model. †Post-hoc analyses. ‡Prespecified exploratory analyses.

Citation Format: Javier Cortes, David W. Cescon, Hope S. Rugo, Zbigniew Nowecki, Seock-Ah Im, Mastura Md Yusof, Carlos Gallardo, Oleg Lipatov, Carlos Henrique Barrios, Jose Perez-Garcia, Hiroji Iwata, Norikazu Masuda, Marco Torregroza Otero, Erhan Gokmen, Sherene Loi, Zifang Guo, Xuan Zhou, Vassiliki Karantza, Wilbur Pan, Peter Schmid. Final results of KEYNOTE-355: Randomized, double-blind, phase 3 study of pembrolizumab + chemotherapy vs placebo + chemotherapy for previously untreated locally recurrent inoperable or metastatic triple-negative 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 GS1-02.

Abstract PD10-02: A randomised phase II trial of single fraction or multi-fraction SABR (stereotactic ablative body radiotherapy) with atezolizumab in patients with advanced triple negative breast cancer (AZTEC trial)

A randomised phase II trial of single fraction or multi-fraction SABR (stereotactic ablative body radiotherapy) with atezolizumab in patients with advanced triple negative breast cancer (AZTEC trial) Abstract: BACKGROUND: In patients with advanced triple negative breast cancer (TNBC), immunotherapy has shown acceptable safety and efficacy in a PD-L1 (programmed death-ligand 1) positive population. Pre-clinical evidence has demonstrated that SABR can prime a more effective systemic anti-tumor response in combination with checkpoint inhibition. It is currently unknown if single or multi-fraction SABR scheduling synergises best with atezolizumab therapy. METHODS: This was a multi-centre, open label, phase 2 randomised trial of patients with advanced TNBC, unselected for (PD-L1) status, who had recurred at least 6 months post completion of (neo) adjuvant chemotherapy and received less than 2 lines of treatment in the metastatic setting. Participants were randomised to 20Gy SABR in 1 fraction or 24Gy SABR in 3 fractions to 1-4 sites of disease, with at least one metastasis left unirradiated. Within 5 days following the final fraction of radiotherapy atezolizumab was commenced at a dose of 1200 mg every 21 days and continued for up to 24 months, or until progression or intolerable toxicity. The primary endpoint is progression- free survival (PFS). Secondary endpoints include efficacy according to PD-L1 IHC status (positive: SP142 ≥1%) and TIL (tumour infiltrating lymphocyte) quantity, response assessment, overall survival and safety. Results presented are from interim analysis performed 18 weeks after the last patient commenced treatment. RESULTS: Fifty evaluable patients were recruited and randomised between 20th November 2018 and 12thApril 2021 with a median age of 57 [35 - 79] yrs. Thirty (60%) and 20 (40%) patients had received none or one previous line of chemotherapy in the metastatic setting, respectively. 14/40 (35%) patients were PD-L1 positive at baseline and 26/42 (62%) had TIL≥5%. Median follow-up was 17 months. The median PFS for the 20 Gy arm was 2.5 (90% CI: 1.7-4.5) months, 3.1 (90% CI: 1.8-3.9) months for the 24 Gy arm. For both arms combined, the PFS was 3.1 (90% CI: 1.8-3.9) months, with no difference between the arms, HR 1.2 (95% CI: 0.6-2.1), p=0.64. PFS by PD-L1 IHC status and TIL&lt;5% vs ≥5% was similar. There were 11 (22%) patients with clinical benefit (no PD within 24 weeks of C1D1), these were not significantly different by arm (p=0.74), nor by PD-L1 status (p=0.44) or TIL quantity (p=0.92) (Table 1). Overall survival is immature: estimated 12 months was 78% (95% CI:54-90) for the 20 Gy arm and 57% (95% CI: 33-75) for the 24 Gy arm.. In patients who were PD-L1 positive the ORR was 1/12 (8%) and DC was 3/14 (21%) compared with ORR of 1/14 (7%) and DC of 3/26 (12%) in patients who were PD-L1 negative.

CONCLUSIONS: The efficacy between single and multi-fraction SABR in combination with Atezolizumab was similar and toxicity was acceptable. Efficacy was seen in PD-L1 positive and negative patients. Longer follow-up is required to assess the effect on OS.. (Research support and funding provided by the imCORE Network on behalf of F. Hoffmann-La Roche; AZTEC ClinicalTrials.gov Identifier: NCT03464942)

Table 1.Response AssessmentResponse, n (%)All patients (n = 50)Patients with measurable disease (n = 32)Best objective response (non-SABR lesion)CR3 (6)2 (6)PR2 (4)2(6)NCR/NPD8 (16)0SD13 (26)13 (41)PD24 (48)15 (47)ORR (CR + PR)5 (10); 95% CI: 3-224 (12%); 95% CI: 4-29DCR (CR + PR + SD + non-CR/non-PD ≥24 weeks)a11 (22%); 95% CI: 12-377 (23%); 95% CI: 10-41aOne patient withdrew at 8 weeks and was not assessable for DCR.

Citation Format: Steven David, Peter Savas, Shankar Siva, Michelle White, Michael W Neeson, Shane White, Gavin Marx, Robyn Cheuk, Michelle Grogan, Maria Farrell, Jessica Foudoulis, Annette Dempsey, Paul J Neeson, Mathias Bressel, Sherene Loi. A randomised phase II trial of single fraction or multi-fraction SABR (stereotactic ablative body radiotherapy) with atezolizumab in patients with advanced triple negative breast cancer (AZTEC 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 PD10-02.

Stereotactic Radiotherapy and Short-course Pembrolizumab for Oligometastatic Renal Cell Carcinoma-The RAPPORT Trial

BACKGROUND

Stereotactic ablative body radiotherapy (SABR) is an option for oligometastatic clear cell renal cell carcinoma (ccRCC) but is limited by a lack of prospective clinical trial data.

OBJECTIVE

The RAPPORT trial evaluated the safety and efficacy of total metastatic irradiation followed by short-course anti-programmed death receptor-1 immunotherapy in patients with oligometastatic ccRCC.

DESIGN SETTING, AND PARTICIPANTS

RAPPORT was a single-arm multi-institutional phase I/II trial (NCT02855203). Patients with two or fewer lines of prior systemic therapy and one to five oligometastases from ccRCC were eligible.

INTERVENTION

A single fraction of 20 Gy SABR (or if not feasible, ten fractions of 3 Gy) was given to all metastatic sites, followed by pembrolizumab 200 mg administered Q3W for eight cycles.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The endpoints were adverse events (AEs), disease control rate (DCR) for at least 6 mo, objective response rate (ORR), progression-free survival (PFS), and overall survival (OS). The Kaplan-Meier method was used for time-to-event endpoints. Freedom from local progression (FFLP) was assessed per lesion adding patient as a cluster effect.

RESULTS AND LIMITATIONS

Thirty evaluable patients, with a median age of 62 yr, were enrolled. The median follow-up was 28 mo. There were 44% of patients with intermediate-risk and 56% with favorable-risk disease. Eighty-three oligometastases were irradiated (median three per patient): eight adrenal, 11 bone, 43 lung, 12 lymph node, and nine soft tissue. Four patients (13%) had grade 3 treatment-related AEs: pneumonitis (n = 2), dyspnea (n = 1), and elevated alkaline phosphatase/alanine transaminase (n = 1). There were no grade 4 or 5 AEs. FFLP at 2 yr was 92%. ORR was 63% and DCR was 83%. Estimated 1- and 2-yr OS was 90% and 74%, respectively, and PFS was 60% and 45%, respectively. Limitations include a single-arm design and selected patient population.

CONCLUSIONS

SABR and short-course pembrolizumab in oligometastatic ccRCC is well tolerated, with excellent local control. Durable responses and encouraging PFS were observed, warranting further investigation.

PATIENT SUMMARY

The RAPPORT trial investigated the combination of high-dose precision radiotherapy and a short course of immunotherapy in patients with low-volume metastatic kidney cancer. We found that this treatment regimen was well tolerated, with excellent cancer control in sites of known disease. A proportion of patients were free from cancer relapse in the longer term, and these encouraging findings warrant further investigation.

The tale of TILs in breast cancer: A report from The International Immuno-Oncology Biomarker Working Group

The advent of immune-checkpoint inhibitors (ICI) in modern oncology has significantly improved survival in several cancer settings. A subgroup of women with breast cancer (BC) has immunogenic infiltration of lymphocytes with expression of programmed death-ligand 1 (PD-L1). These patients may potentially benefit from ICI targeting the programmed death 1 (PD-1)/PD-L1 signaling axis. The use of tumor-infiltrating lymphocytes (TILs) as predictive and prognostic biomarkers has been under intense examination. Emerging data suggest that TILs are associated with response to both cytotoxic treatments and immunotherapy, particularly for patients with triple-negative BC. In this review from The International Immuno-Oncology Biomarker Working Group, we discuss (a) the biological understanding of TILs, (b) their analytical and clinical validity and efforts toward the clinical utility in BC, and (c) the current status of PD-L1 and TIL testing across different continents, including experiences from low-to-middle-income countries, incorporating also the view of a patient advocate. This information will help set the stage for future approaches to optimize the understanding and clinical utilization of TIL analysis in patients with BC.

PD-L1 Immunohistochemistry Assay Comparison in Atezolizumab Plus nab-Paclitaxel-Treated Advanced Triple-Negative Breast Cancer

BACKGROUND

In the phase III IMpassion130 study, atezolizumab plus nab-paclitaxel (A+nP) showed clinical benefit in advanced or metastatic triple-negative breast cancer patients who were programmed death-ligand 1 (PD-L1)+ (tumor-infiltrating immune cells [IC] ≥1%) using the SP142 immunohistochemistry assay. Here we evaluate 2 other PD-L1 assays for analytical concordance with SP142 and patient-associated clinical outcomes.

METHODS

Samples from 614 patients (68.1% of intention-to-treat population) were centrally evaluated by immunohistochemistry for PD-L1 status on IC (VENTANA SP142, SP263, Dako 22C3) or as a combined positive score (CPS; 22C3).

RESULTS

Using SP142, SP263, and 22C3 assays, PD-L1 IC ≥1% prevalence was 46.4% (95% confidence interval [CI] = 42.5% to 50.4%), 74.9% (95% CI = 71.5% to 78.3%), and 73.1% (95% CI = 69.6% to 76.6%), respectively; 80.9% were 22C3 CPS ≥1. At IC ≥1% (+), the analytical concordance between SP142 and SP263 and 22C3 was 69.2% and 68.7%, respectively. Almost all SP142+ cases were captured by other assays (double positive), but several SP263+ (29.6%) or 22C3+ (29.0%) cases were SP142- (single positive). A+nP clinical activity vs placebo+nP in SP263+ and 22C3+ patients (progression-free survival [PFS] hazard ratios [HRs] = 0.64 to 0.68; overall survival [OS] HRs = 0.75 to 0.79) was driven by double-positive cases (PFS HRs = 0.60 to 0.61; OS HRs = 0.71 to 0.75) rather than single-positive cases (PFS HRs = 0.68 to 0.81; OS HRs = 0.87 to 0.95). Concordance for harmonized cutoffs for SP263 (IC ≥4%) and 22C3 (CPS ≥10) to SP142 (IC ≥1%) was subpar (approximately 75%).

CONCLUSIONS

22C3 and SP263 assays identified more patients as PD-L1+ (IC ≥1%) than SP142. No inter-assay analytical equivalency was observed. Consistent improved A+nP efficacy was captured by the SP142 PD-L1 IC ≥1% subgroup nested within 22C3 and SP263 PD-L1+ (IC ≥1%) populations.

Genomic and Transcriptomic Analyses of Breast Cancer Primaries and Matched Metastases in AURORA, the Breast International Group (BIG) Molecular Screening Initiative

AURORA aims to study the processes of relapse in metastatic breast cancer (MBC) by performing multi-omics profiling on paired primary tumors and early-course metastases. Among 381 patients (primary tumor and metastasis pairs: 252 targeted gene sequencing, 152 RNA sequencing, 67 single nucleotide polymorphism arrays), we found a driver role for GATA1 and MEN1 somatic mutations. Metastases were enriched in ESR1, PTEN, CDH1, PIK3CA, and RB1 mutations; MDM4 and MYC amplifications; and ARID1A deletions. An increase in clonality was observed in driver genes such as ERBB2 and RB1. Intrinsic subtype switching occurred in 36% of cases. Luminal A/B to HER2-enriched switching was associated with TP53 and/or PIK3CA mutations. Metastases had lower immune score and increased immune-permissive cells. High tumor mutational burden correlated to shorter time to relapse in HR+/HER2- cancers. ESCAT tier I/II alterations were detected in 51% of patients and matched therapy was used in 7%. Integration of multi-omics analyses in clinical practice could affect treatment strategies in MBC. SIGNIFICANCE: The AURORA program, through the genomic and transcriptomic analyses of matched primary and metastatic samples from 381 patients with breast cancer, coupled with prospectively collected clinical data, identified genomic alterations enriched in metastases and prognostic biomarkers. ESCAT tier I/II alterations were detected in more than half of the patients.This article is highlighted in the In This Issue feature, p. 2659.