1475 - Alpelisib (ALP) + Fulvestrant (FUL) in Hormone-Receptor Positive (HR+), Human Epidermal Growth Factor Receptor-2–Negative (HER2–) Advanced Breast Cancer (ABC): Subgroup Analysis by Presence of Visceral Metastasis (VM) in the SOLAR-1 Trial

Background

Approximately 40% of patients (pts) with HR+, HER2– BC have mutations (mut) in PIK3CA with hyperactivation of the PI3K pathway and relative endocrine resistance. In the phase 3 SOLAR-1 trial, treatment with the α-selective PI3K inhibitor ALP with FUL significantly prolonged progression-free survival (PFS) vs placebo [PBO] + FUL in the PIK3CA-mut cohort (median PFS [mPFS], 11.0 vs 5.7 mo; HR 0.65; P < 0.001). Here, we report data for pts with and without VM in the PIK3CA-mut cohort of SOLAR-1.

Methods

Pts with HR+, HER2– ABC with progression on/after aromatase inhibitor received ALP 300 mg QD (or PBO) + FUL 500 mg. Efficacy, including PFS and response, and safety were assessed. Pts were stratified according to presence of lung and/or liver metastases and prior CDK4/6 inhibitor treatment.

Results

Of 341 pts with PIK3CA mut, 193 (56.6%) had VM. Tumor responses were improved with ALP vs PBO in pts with or without VM (Table). The majority (n = 170; 88.1%) of pts with VM had lung and/or liver metastases and mPFS was 9.0 vs 3.7 mo in the ALP (n = 84) vs PBO (n = 86) arms (HR 0.62; 95% CI, 0.44-0.89). PFS HRs (95% CI) for ALP vs PBO in pts with presence of liver metastases (ALP, n = 49; PBO, n = 54) or lung involvement (ALP, n = 57; PBO, n = 68) were 0.58 (0.37-0.90) and 0.65 (0.42-1.01), respectively. PFS HRs (95% CI) for ALP vs PBO in pts without lung and/or liver metastases (ALP, n = 85; PBO, n = 86) and in pts with bone-only metastases (ALP, n = 42; PBO, n = 35) were 0.69 (0.47-1.01) and 0.62 (0.33-1.18), respectively. mPFS for pts with bone-only metastases in the ALP vs PBO arms was 19.1 vs 13.0 mo.Table:

342P

Conclusions

Treatment benefit from ALP + FUL was maintained across pt subgroups analyzed, including pts with VM and bone-only metastases, and was consistent with the benefit observed in the PIK3CA-mut cohort in SOLAR-1.

Clinical trial identification

NCT02437318.

Editorial acknowledgement

Medical editorial assistance was provided by Joe Hodgson and Amanda Vreeland, PhD, of Healthcare Consultancy Group, LLC, and funded by Novartis Pharmaceuticals Corporation.

Legal entity responsible for the study

Novartis Pharmaceutical Corporation.

Funding

Novartis Pharmaceutical Corporation.

Disclosure

M. Campone: Research grant / Funding (self), Grant: Novartis; Research grant / Funding (self), Personal fee: Roche; Research grant / Funding (self), Personal fee: AstraZeneca; Research grant / Funding (self), Personal fee: Pfzier; Advisory / Consultancy, Advisory board fees to the institution: Servier; Advisory / Consultancy, NA: Lilly; Advisory / Consultancy, Advisory board fees to the institution: Sanofi; Advisory / Consultancy, Advisory board fees to the institution: Accord; Research grant / Funding (self), Grant: Tessaro. H.S. Rugo: Research grant / Funding (self), Research: Pfizer, Merck, Novartis, Lilly, Genentech, OBI, Odonate, Daiichi, Eisai, Seattle Genetics and Macrogenics; Travel / Accommodation / Expenses, Travel: Lilly, Mylan, Pfizer, Amgen, Merck and Puma. G. Rubovszky: Advisory / Consultancy, Conduct of clinical trials as investigator: Novartis. F. André: Research grant / Funding (institution), Research: Novartis, AstraZeneca, Pfizer, Lilly, Roche. S. Loibl: Honoraria (institution), honorario: Novartis; Honoraria (institution), honorario: Pfzier; Honoraria (institution), honorario: Amgen; Honoraria (institution), honorario: Celgene; Honoraria (institution), honorario: Roche; Honoraria (institution), honorario: AstraZeneca; Honoraria (institution), honorario: Abbvie; Honoraria (institution), honorario: Lilly; Honoraria (institution), honorario: Daichi; Honoraria (institution), honorario: Eirgenix. H. Iwata: Honoraria (institution), Advisory / Consultancy, Support of parent study and funding of editorial support, honoraria and consulting: Novartis; Honoraria (institution), Advisory / Consultancy, Consulting: F. Hoffmann-La Roche via Chugai; Honoraria (institution), Advisory / Consultancy, Consulting: AstraZeneca; Honoraria (institution), Advisory / Consultancy, Consulting: Lilly; Honoraria (institution), Advisory / Consultancy, Consulting: Pfzier; Honoraria (institution), Advisory / Consultancy, Consulting: Daiichi-Sankyo. P.F. Conte: Speaker Bureau / Expert testimony, Speakers Bureau: Roche/Genentech; Novartis; AstraZeneca; Research grant / Funding (institution), Research: Roche Relationship (Institution); Novartis (Institution); Merck Serono (Institution); Travel / Accommodation / Expenses, Travel: Novartis; Celgene;AstraZeneca. I. Mayer: Research grant / Funding (institution), Institutional research funding and Ad board: Novartis; Research grant / Funding (institution), Institutional research funding and Ad board: Genentech; Research grant / Funding (institution), Institutional research funding: Pfzier; Advisory / Consultancy, Ad board: Eli-Lilly; Advisory / Consultancy, Ad board: AstraZeneca; Advisory / Consultancy, Ad board: GSK; Advisory / Consultancy, Ad board: Macrogenics; Advisory / Consultancy, Ad board: Seattle Genetics; Advisory / Consultancy, Ad board: Immunomedic. D. Juric: Advisory / Consultancy, Scientific Advisory Board: Novartis; Speaker Bureau / Expert testimony, Scientific Advisory Board: Genentech; Advisory / Consultancy, Scientific Advisory Board: Eisai; Advisory / Consultancy, Scientific Advisory Board: Ipsen; Advisory / Consultancy, Scientific Advisory Board: EMD Serono. T. Yamashita: Honoraria (self), Research grant / Funding (self): Chugai; Honoraria (self), Research grant / Funding (self): Nippon Kayaku; Honoraria (self), Research grant / Funding (self): Kyowa Kirin; Honoraria (self): Eisai, Novartis, Taiho, AstraZeneca, Pfzier Japan. I. Lorenzo: Full / Part-time employment, Employee: Novartis. A. Ridolfi: Full / Part-time employment, Employee: Novartis. E.M. Ciruelos: Honoraria (self), honorario: Consultancy for Novartis, Lilly, Roche, Pfizer; Advisory / Consultancy, Consulting: Novartis, Pfizer, Lilly, Roche; Speaker Bureau / Expert testimony, Speakers Bureau: Novartis, Pfizer, Lilly, Roche; Travel / Accommodation / Expenses, Travel: Roche, Pfizer.