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.

Matching-adjusted indirect comparison of PFS and OS comparing ribociclib plus letrozole versus palbociclib plus letrozole as first-line treatment of HR+/HER2- advanced breast cancer.

Background: Current standard-of-care first-line treatment of patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced breast cancer (ABC) is cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) + endocrine therapy. In the MONALEESA-2 trial, first-line ribociclib + letrozole demonstrated statistically significant overall survival (OS) benefit versus placebo + letrozole in postmenopausal patients with HR+/HER2- ABC. In the PALOMA-2 trial, first-line palbociclib + letrozole did not show OS benefit versus placebo + letrozole in a similar patient population. Understanding OS outcomes in the respective trials is critical for treatment decisions; however, there are no head-to-head clinical trial data comparing ribociclib and palbociclib. Objectives: To conduct a matching-adjusted indirect comparison (MAIC) to compare progression-free survival (PFS) and OS of first-line ribociclib + letrozole versus palbociclib + letrozole in postmenopausal patients with HR+/HER2- ABC. Design: Letrozole-anchored MAIC using individual patient data from MONALEESA-2 and published summary data from PALOMA-2. Methods: Using individual data, patients from MONALEESA-2 who matched inclusion criteria from PALOMA-2 were selected, and weighting was conducted to ensure baseline characteristics were similar to those in published aggregated data from PALOMA-2. The Bucher method was used to generate corresponding hazard ratios (HRs). Results: The final effective sample size compared n = 150 (ribociclib) and n = 112 (placebo) MONALEESA-2 patients with n = 444 (palbociclib) and n = 222 (placebo) PALOMA-2 patients. After matching and weighting, patient characteristics were well balanced. MAIC analysis showed a numerical PFS benefit [HR, 0.80; 95% confidence interval (CI), 0.58-1.11; p = 0.187] and significant OS benefit (HR, 0.68; 95% CI, 0.48-0.96; p = 0.031) with ribociclib + letrozole versus palbociclib + letrozole. Conclusion: Results of this cross-trial MAIC analysis showed a numerical PFS benefit and significantly greater OS benefit with first-line ribociclib + letrozole versus palbociclib + letrozole. These results support letrozole + ribociclib as the preferred first-line CDK4/6i for postmenopausal patients with HR+/HER2- ABC. Trial registration: NCT01958021; https://www.clinicaltrials.gov/study/NCT01958021 (MONALEESA-2) and NCT01740427; https://clinicaltrials.gov/study/NCT01740427 (PALOMA-2).

Matching-Adjusted Indirect Comparison of Ribociclib Plus Fulvestrant versus Palbociclib Plus Letrozole as First-Line Treatment of HR+/HER2- Advanced Breast Cancer.

PURPOSE: Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) plus endocrine therapy are recommended for first-line treatment of hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced breast cancer (ABC). However, not all CDK4/6i trials have reported significant overall survival (OS) benefit, and there have been no head-to-head trials. Two trials have reported OS outcomes in first-line patients: MONALEESA-3 reported significant OS benefit with first- or second-line ribociclib plus fulvestrant (RIB+FUL) versus placebo plus fulvestrant (PBO+FUL), while PALOMA-1 reported no significant OS benefit for palbociclib plus letrozole (PAL+LET) versus LET in first-line postmenopausal patients. Matched-adjusted indirect comparisons (MAICs) are an established method for comparing efficacy of treatments from different trials. We used an MAIC to compare first-line patients from MONALEESA-3 and PALOMA-1. PATIENTS AND METHODS: An unanchored MAIC of progression-free survival (PFS) and OS in first-line patients with HR+/HER2- ABC treated with RIB+FUL versus PAL+LET was conducted using individual patient data from MONALEESA-3 and aggregated data from PALOMA-1. To match patients in PALOMA-1, patients in MONALEESA-3 were limited to those with no prior endocrine therapy for ABC and no (neo) adjuvant LET ≤12 months before enrollment. PFS and OS were compared using Kaplan-Meier estimators and Cox regression. RESULTS: A total of 329 and 178 patients from RIB+FUL and PBO+FUL arms, respectively, of MONALEESA-3 were matched to 84 and 81 patients from PAL+LET and LET arms of PALOMA-1. After weighting, OS was significantly longer for RIB+FUL versus PAL+LET (hazard ratio [HR], 0.50; 95% CI, 0.32-0.77; p = 0.0020). PFS favored RIB+FUL versus PAL+LET, although the difference was not statistically significant (HR, 0.77; 95% CI, 0.54-1.10; p = 0.1553). CONCLUSION: Using MAIC to adjust for trial differences, OS comparisons favored RIB+FUL over PAL+LET as first-line treatment in postmenopausal patients with HR+/HER2- ABC. These exploratory results suggest a significant increase in OS benefit with RIB treatment compared with PAL.