Abstract PO5-22-08: Comparison of long-term oncological outcomes in young women with breast cancer between BRCA-mutation carriers versus non-carriers: How genetic risk factors and tumor characteristics influence the prognosis

Abstract Objectives and rationale: Breast cancer (BC) arising at a young age is relatively uncommon; however, approximately 6 to 10% of women diagnosed with BC are younger than the age 40. This subgroup of young women presents different risk factors, tumor biology, and clinical outcomes. Moreover, the interpretation of the effects of inherited genetic factors on the prognosis of young patients with BC remains a subject of debate. The primary aim of this study was to evaluate the characteristics of young patients with BC and to compare the long-term oncological results between BRCA-mutation carriers and non-carriers. We retrospectively reviewed all the consecutive young (≤ 40 years old) BC patients treated at the Breast Unit of IRCCS Humanitas Research Hospital (Milan, Italy). All young patients underwent BRCA-mutation analysis. For further analysis young BC patients were divided into two groups: BRCA-mutation carriers versus non-carriers. Tumor, surgical treatment, and post-operative data were compared between the two groups. Primary end-points were: disease-free survival (DFS), distant disease-free survival (DDFS), and overall survival (OS). The Kaplan-Meier method was used to generate the recurrence and survival curves. Multivariate analyses were performed using the Cox proportional hazards model to identify independent risk and protective factors for DFS, DDFS, and OS. Results: The characteristics of 63 young BC patients with BRCA-mutation were compared with 339 young BC patients without BRCA-mutation. BRCA-mutation carriers tend to be younger (60.3% versus 34.8% if age ≤ 35 years, odds ratio (OR) = 17.699, 95% confidence interval (95%CI) = 33.871-35.568, p = 0.001) and present more aggressive tumors (66.7% versus 40.7% if G3, OR = 17.119, 95%CI = 2.549-2.828, p = 0.001; 57.2% versus 12.4% if biological subtype triple negative, OR = 52.727, 95%CI = 2.042-2.417, p = 0.001; 73.0% versus 39.2% if Ki67 ≥ 25%, OR = 58.981, 95%CI = 47.135-58.505, p = 0.001). Young BC patients without BRCA-mutation presented significantly better long-term oncological results in terms of DFS, DDFS, and OS compared with young BRCA-mutation carriers (10-years DFS rate 91.1% versus 58.1%, p 0.001; 10-year DDFS rate 91.2% versus 76.1%, p = 0.003; 10-year OS rate 98.0% versus 87.8%, p = 0.002, respectively). Neo-adjuvant chemotherapy was found to be an independent protective factor for OS in young BRCA-mutated BC patients (hazard radio = 14.885, 95%CI = 2.343-94.566, p = 0.004). Conclusions: Breast cancer is more likely to present at a younger age (≤ 35 years) and with more aggressive characteristics (G3, triple negative, Ki67 ≥ 25%) in patients with BRCA-mutation compared with their non-mutated counterpart. Young BRCA-mutation carriers show a poorer prognosis in terms of recurrence and survival compared with non-carriers. The implementation of neo-adjuvant chemotherapy may improve survival in young BC patients with BRCA-mutation. Citation Format: Damiano Gentile, Simone Di Maria Grimaldi, Andrea Sagona, Erika Barbieri, Alberto Bottini, Giuseppe Canavese, Giulia Caraceni, Shadya Darwish, Corrado Tinterri. Comparison of long-term oncological outcomes in young women with breast cancer between BRCA-mutation carriers versus non-carriers: How genetic risk factors and tumor characteristics influence the prognosis 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 PO5-22-08.