Goyal RK, Zhang J, Davis KL, Kaufman PA. Real-world treatment patterns and clinical outcomes in patients treated with eribulin after prior PI3K inhibitor therapy for metastatic breast cancer. Poster presented at the 2022 San Antonio Breast Cancer Symposium (SABCS); December 6, 2022. San Antonio, TX.

BACKGROUND: Eribulin has been used in the treatment of metastatic breast cancer (MBC) following approval in 2010 in the United States (US). Recently, several new therapeutic classes have been approved for patients with MBC, including the phosphoinositide 3-kinase (PI3K) inhibitor alpelisib. This study aimed to assess the treatment patterns and clinical outcomes in patients with MBC treated with eribulin following alpelisib in US clinical practice.

METHODS: A retrospective, noninterventional medical chart review study was performed to obtain de-identified patient data via participating oncologists. Study population included adult female patients with a diagnosis of MBC who initiated eribulin therapy between March 1, 2019, and September 30, 2020, following prior therapy with alpelisib. Eribulin treatment parameters and patient characteristics were captured. Progression-free survival (PFS) and overall survival (OS) since eribulin initiation was assessed using Kaplan-Meier methods.

RESULTS: This interim analysis included 47 eligible patients (median age 62 years at eribulin initiation; 77% Caucasian). The majority (91.5%) of this cohort had HR+/HER2– MBC; 72.3% had a known PIK3CA mutation. Eribulin was classified as 2nd line, 3rd line, and 4th line or later in 34%, 47%, and 19% of patients, respectively, in regard to the line of therapy in the metastatic setting. At last follow-up, eribulin treatment was ongoing for 34% of patients. The median treatment duration was 5.2 months (q1, q3: 3.9, 7.1) among those who had discontinued eribulin, and 11.3 months (q1, q3: 10.0, 13.7) among those who were still on treatment. At last follow-up, 72.3% of patients were alive. The estimated PFS rate at 12 months was 57.1% (95% CI: 40.0-70.9). Median was not reached for OS after initiation of eribulin; the estimated OS rates at 12 and 24 months were 80.2% (95% CI: 65.3-89.2) and 61.8% (95% CI: 37.2-79.2), respectively.

CONCLUSION: Among patients with MBC who initiated eribulin following prior treatment with a PI3K inhibitor, over 60% were estimated to survive for at least 2 years. Future studies to confirm these results are warranted.

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