Abstract PO2-06-02: Characteristics and Treatment Patterns of de novo Oligometastatic Stage IV Breast Cancer: A Single-Center Retrospective Cohort Study

Abstract Background: Retrospective studies suggest that patients with oligometastatic breast cancer (≤ 5 metastatic lesions) have improved prognosis and may benefit from multimodality treatment. Randomized clinical trials, however, with mostly recurrent oligometastatic breast cancer have not shown improved prognosis with this approach. Real-world data on de novo oligometastatic stage IV (oligo-stage IV) disease are limited. We therefore investigated differences in 5-year mortality in patients with de novo oligo-stage IV vs de novo extensive-stage IV breast cancer who received curative vs palliative chemotherapy at our institution. Methods: In a retrospective cohort design, using the Yale tumor registry, we identified de novo stage IV breast cancer (metastatic to distant sites at diagnosis), diagnosed 2012-2016. Clinical characteristics and treatment patterns were compared between oligo-stage IV vs extensive-stage IV. Curative regimens were defined as TCHP or AC-THP for HER2+, ddAC- T or TC for ER+, and ddAC- T for TNBC. Palliative regimens were defined as THP for HER2+ or single agent chemotherapy. 5-year mortality rates were calculated from date of diagnosis to date of death, with living patients censored at date of last contact. Kaplan-Meier curves were estimated and compared using log-rank tests. Multivariable Cox proportional hazards models assessed the association between oligo-stage IV vs extensive-stage IV breast cancer, curative vs palliative regimen, and 5-year mortality. Models were adjusted for receptor status, age at diagnosis, receipt of surgery, and radiation. Models were then stratified by receptor status. Results: Of the 202 de novo stage IV cases, 140 (69.3%) were extensive-stage IV and 62 (30.4%) were oligo-stage IV. A larger proportion of oligo-stage IV vs extensive-stage IV was TNBC (19.4% vs 8.8%, p=0.03), lower proportion was ER+ (65.6% vs 81.5%, p=0.01), and no difference in HER2 (30.5% vs 29.0%, p=0.83). Higher proportion of oligo-stage IV vs extensive-stage IV received curative chemotherapy (24.2% vs 7.9%, p 0.001) and breast surgery (25.0% vs 13.6%, p 0.001). There was no difference in receipt of radiation to distant sites (25.0% vs 27.5%, p=0.70). Patients who received curative vs palliative chemotherapy were younger (55.3 vs 62.1yo, p=0.02). Oligo-stage IV had lower 5-year mortality (64.7%) vs extensive-stage IV (70.6%; HR=0.58, 95% CI 0.39-0.89), with no significant difference in 5-year mortality between curative vs palliative chemotherapy. When stratifying by receptor status, ER+ had the strongest association between oligo-stage IV and decreased 5-year mortality (HR=0.56, 95% CI 0.34 – 0.92). There was no significant association between surgery or radiation and 5-year mortality (HR = 0.62, 95% CI 0.38-0.99; HR= 1.33, 95% CI 0.91-1.95, respectively). Only a small number of patients received all 3 components; curative chemotherapy, surgery, and radiation (N=5; 18.5%). The dose of radiation (palliative vs ablative) is unknown. Conclusions: Patients with oligo-stage IV breast cancer had lower 5-year mortality vs extensive-stage IV breast cancer. Neither curative intent chemotherapy, breast surgery nor radiation were associated with lower 5-year mortality. However, very few patients received all 3 modalities with curative intent. These results are consistent with prior randomized clinical trials that showed no survival benefit to escalating therapy, but leave the question unanswered if combining all 3 modalities may improve overall survival in de novo oligometastatic stage IV breast cancer. Multivariable-Adjusted Association Between Disease Status and 5-Year Mortality Among Patients with De Novo Stage IV Breast Cancer, Stratified by Receptor Status. *Further adjusted for age at diagnosis; HR – hazard ratio, CI – confidence interval Citation Format: Deanna Blansky, Maryam Lustberg, Lajos Pusztai, Mariya Rozenblit. Characteristics and Treatment Patterns of de novo Oligometastatic Stage IV Breast Cancer: A Single-Center Retrospective Cohort Study 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 PO2-06-02.