Abstract PO4-08-03: Prognostic Effect of Ductal Carcinoma in Situ in Breast Cancer with BRCA1/2 Mutations

Abstract Abstract Background: Although Breast Cancer Susceptibility Gene (BRCA)-associated invasive breast cancer has been extensively studied, there are few reports on ductal carcinoma in situ (DCIS) in patients with BRCA1/2 mutations. This study aims to evaluate the prognostic effect of DCIS in breast cancer patients with pathologic variants of BRCA1/2 genes. Methods: Retrospective analysis was performed on a prospective cohort of 157 patients who were found positive for BRCA1/2 mutations through genetic testing from August 2003 to January 2022 at Seoul National University Bundang Hospital. Survival outcomes were compared between patients who had both invasive ductal carcinoma (IDC) and DCIS components (IDC-DCIS group, n = 121) and patients who had IDC only (IDC group, n = 36). Cox regression analysis was performed for evaluation of predictive factors for recurrence. Results: Among the 157 patients, 65 (41.4%) patients showed BRCA1 mutations, 90 (57.3%) patients had pathological variants of BRCA2, and 2 (1.3%) patients tested positive for both BRCA1/2 mutations. There was no difference in baseline clinical characteristics between the IDC-DCIS and IDC groups. When pathological features were compared, the IDC-DCIS group was more likely to express positivity in both estrogen receptor (IDC 5 (13.9%) vs. IDC-DCIS 74 (61.2%), P 0.001) and progesterone receptor status (IDC 5 (13.9%) vs. IDC-DCIS 67 (55.4%), P 0.001). Tumors in the IDC group were associated with a higher histologic grade (P = 0.004). There was no statistically significant difference in 5-year disease-free survival between the two groups (IDC 83.6% vs. IDC-DCIS 89.3%, P = 0.989). In univariate Cox regression analysis, younger age at diagnosis was a significant predictor for recurrence (hazard ratio (HR) 2.236, P = 0.049); salpingo-oophorectomy showed a risk-reducing effect (HR 0.106, P 0.001). Further multivariate analysis found only the effect of salpingo-oophorectomy to be prognostic (HR 0.112, P 0.001). Presence of DCIS was not a risk factor for recurrence in patients with BRCA1/2 mutations (HR 1.006, P = 0.989). Conclusion: BRCA1/2-positive breast cancer with DCIS components is more likely to be hormone receptor-positive and of lower grade compared to patients with IDC only. A tailored approach might be necessary in establishing treatment options for breast cancer patients with BRCA1/2 mutations according to the presence of DCIS. Citation Format: Kyung-Hwak Yoon, Eun-Kyu Kim, Hee-Chul Shin. Prognostic Effect of Ductal Carcinoma in Situ in Breast Cancer with BRCA1/2 Mutations 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 PO4-08-03.