Prognostic implications of ductal carcinoma in situ components in BRCA1/2-positive breast cancer: a retrospective cohort study.

Purpose: Although the breast cancer susceptibility gene (BRCA)-associated invasive breast cancer is well studied, there are limited reports on ductal carcinoma in situ (DCIS) in patients with BRCA1/2 mutations. This study aims to evaluate the differential prognostic effect of DCIS in breast cancer patients with pathologic variants of BRCA1/2 genes.

Methods: Breast cancer patients who tested positive for BRCA1/2 mutations between August 2003 and January 2022 at a single tertiary referral center were retrospectively analyzed. Survival outcomes were compared between patients with both invasive ductal carcinoma (IDC) and DCIS (IDC-DCIS group, n = 121) and those with IDC alone (IDC group, n = 36).

Results: Of the 157 patients, 65 (41.4%) exhibited mutations in BRCA1, 90 (57.3%) in BRCA2, and 2 (1.3%) in both BRCA1/2. DCIS components were more frequently found in BRCA2 pathological variants (BRCA1, 46 [38.0%] vs. BRCA2, 76 [62.4%]; P = 0.030). No statistically significant difference was found in 10-year recurrence-free survival (IDC-DCIS, 89.3% vs. IDC, 83.6%; P = 0.989). Subgroup analysis indicated that the DCIS component correlated with improved survival outcomes in the BRCA1 subgroup (BRCA1 IDC-DCIS, 85.5% vs. BRCA1 IDC, 51.0%; P = 0.024). Conversely, in the BRCA2 subgroup, IDC-DCIS patients exhibited a worse prognosis (BRCA1 IDC-DCIS, 85.5% vs. BRCA2 IDC-DCIS, 65.8%; P = 0.045).

Conclusion: The presence of a DCIS component carries varied prognostic significance in BRCA1 and BRCA2 mutations. A tailored approach may be necessary when determining treatment options for breast cancer patients with BRCA1/2 mutations based on the presence of DCIS.