Abstract PO2-10-07: Patterns of presentation, treatment and survival for older patients with metastatic breast cancer (MBC): results from a large prospective registry

Abstract Background: The median age of breast cancer diagnosis in the U.S. is 62 years; however, older pts with breast cancer are consistently underrepresented in clinical research. In population-based studies, older pts, particularly those aged 70+, do worse than their younger counterparts at every stage of disease, including stage IV. However, our understanding of patterns of recurrence, treatment patterns, and outcomes for older pts with MBC is limited by a lack of available data. Methods: We identified pts age 60 years seen at least once at a single, NCI-designated cancer center for a diagnosis of MBC between 1999-2022 with 1+ years of follow-up from the time of their metastatic diagnosis. We categorized pts into 5-year age groups (60-65; 66-70; 71-75; 76-80; 80) and two groups of 60-70 and 70. Clinicopathologic characteristics, treatment patterns, reason for treatment discontinuation, and the proportion enrolling on clinical trials were compared by tumor subtype and age group using Chi-Square testing. Median overall survival using Kaplan-Meier method was calculated from the date of initial MBC diagnosis to date of death or last follow-up, examined by tumor subtype and age. Results: The final analytic cohort included 1,115 patients diagnosed with MBC with median follow-up of 2.9 years (1.0-18.5). Median age at MBC diagnosis was 66.3 years (60.0-95.4) and 10% were non-White; disease subtype distribution was the following: 70.7% HR+HER2-, 11.9% HER2+, 17.4% TN. Overall, 22.2 presented with de novo MBC. Presentation of MBC did not vary by ages 60-70 vs. 70+, with no differences in disease characteristics such as grade and disease sites at MBC diagnosis (except for bone). However, the proportion of pts with HR+HER2- disease increased with age, from 69% of MBC in ages 60-70 and 76% in ages 70 (p=.02). In pts with this subtype receiving first-line (1L) therapy (n=783), use of endocrine therapy as 1L (with or without a CDK4/6 inhibitor) increased by age (77.8% in ages 60-65 v. 94.7% in ages 80); use of 1L chemotherapy also varied by age (22.2% in ages 60-65 v. 5.3% in 80). Among pts with HER2+ BC, 89% received a trastuzumab-containing regimen in the 1L setting; in pts with TN MBC, 94% received at least 1L line of chemotherapy. Overall, most pts discontinued 1L therapy for progression, not toxicity, and there was no variation in rates of discontinuation due to toxicity by age with 10.4% noted in both age groups, 60-70 and 70. The proportion of patients receiving 3+ lines of chemotherapy across disease subtype decreased with increasing age (e.g., 54% in ages 60-65 v. 25% in ages 80 among HR+HER2-; 69% in ages 60-65 and 33% in ages 80 among TN MBC). Overall, enrollment on a clinical trial in the MBC setting steadily decreased with older age from 40% in ages 60-65 to 13% in ages 80 (p=.0004). Overall median overall survival differed with increasing age from 4.4 yrs in ages 60-65 to 2.7 yrs in ages 80 (p 0.005). In descriptive analyses, the proportion of pts alive at 2 yrs was variable. For those ages 60-65, 37.8%, 17.1%, and 42.9% of pts with HR+HER2, TN, and HR-HER2+, respectively were alive at 2 yrs. For those ages 80, 23.7%, 0%, and 0% of pts with HR+HER2-, TN, and, HR-HER2+ disease were alive at 2 yrs. Median survival times were 2 years for pts with TN regardless of age. Conclusions. In a unique, large prospective cohort of older pts with MBC, we examined detailed information on disease presentation, treatments, and outcomes, lending new information on patterns of care and experiences for older pts with MBC in a modern real-world experience. Limitations include a single center experience and small numbers of older pts with HER2+ and TN disease. Although the oldest pts with MBC had similar disease characteristics as younger pts in our dataset, survival outcomes were poor, particularly for those ages 80+. Therapeutic approaches, likely including improved supportive care, are urgently needed to optimize outcomes in the oldest pts with MBC. Table 1. Outcomes for older pts with MBC Citation Format: Melissa Hughes, Alyssa Patterson, Alexandra Newman, Amanda Higgins, Gregory Kirkner, Janet Files, Molly Skeffington, McKenna Moore, Sarah Strauss, Nicole Kuhnly, Lindsey Crowley, Sara Tolaney, Nancy Lin, Rachel Freedman. Patterns of presentation, treatment and survival for older patients with metastatic breast cancer (MBC): results from a large prospective registry abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-10-07.