LATEBREAKER
Cancer
Characteristics of women with metastatic HR+/HER2+ breast cancer in a Kaiser Permanente observational cohort Sheila Weinmann* Sheila Weinmann Debra P. Ritzwoller Marilyn Kwan Reina Haque Stella Stergiopoulos Ashley Cha-Silva Eric Gauthier Daniel Sapp John Dickerson Weiming Hu Nikki Carroll Lie Hong Chen Valerie Lee Ravi Zalavadi Kathryn Richert-Boe Maureen O’Keeffe-Rosetti
Background: Approximately 10% of female breast cancer tumors express hormone-receptor positive/human epidermal growth factor receptor 2 positive (HR+/HER2+) molecular subtype. This study of the HR+/HER2+ metastatic breast cancer (mBC) patient population describes demographic/clinical characteristics, treatment patterns, and outcomes in a racially diverse, insured, population-based cohort, drawn from four regions of the Kaiser Permanente health system.
Methods: Eligible subjects were women age ≥18 years with HR+/HER2+ invasive breast cancer who were either initially diagnosed with Stage IV disease or were diagnosed at an earlier stage and experienced recurrence with distant metastasis from 2012-2021 with data collected through 2021. Information from electronic health records (EHR) was combined with manually abstracted data to create the analytic dataset.
Preliminary Results: We identified 473 racially and ethnically diverse women with HR+/HER2+ mBC, 46% with de novo Stage 4 breast cancer (D) at diagnosis and 54% with recurrent mBC (R). Median age at mBC diagnosis was 59 years for D cases and 62 years for R cases. Major sites of metastases, including bone, liver, lung, brain, and distant lymph nodes, were similar in D and R groups.
15% of patients received no systemic treatment for their mBC (9% D, 20% R), For those with systemic treatment, 75% received anti-HER2 agents (88% D, 62% R) and 75% received hormone therapy (83% D, 67% R). Of the R cases, 56% received anti-HER2 therapy in the adjuvant setting. Of women who initiated first-line treatment, 68% progressed or died (66% D, 74% R). Median first line progression-free survival was 16 months (23 D, 11 R).
Conclusion:
In this population-based study, 85% of women received systemic therapy, and the majority of those received anti-HER2 therapy per current treatment guidelines.