BRCA1 and BRCA2 Mutations in Polish Women with Ductal Carcinoma In Situ.

Background/Objectives: Ductal carcinoma in situ (DCIS) is the most common non-invasive form of breast cancer. It is not clear to what extent DCIS is a part of the hereditary breast/ovarian cancer syndrome caused by BRCA1/2 mutations. Therefore, we investigated the association of BRCA1/2 mutations in patients with DCIS and assessed their impact on survival. Methods: We studied 564 Polish women with DCIS for six alleles in BRCA1 (c.181T>G, c.5266dupC, c.4035delA, c.3700_3704del5, c.68_69del and c.5251C>T) and four in BRCA2 (c.658_659del, c.3847_3848del, c.5946del and c.7913_7917del). To investigate the association of BRCA1/2 founder mutations with DCIS risk, we tested 4702 controls as a reference. To analyze survival, mutation carriers were followed for an average of 110 months. Results: A BRCA1 mutation was present in seven (1.24%) cases and in twenty-two (0.47%) controls (OR = 3.27, 95%CI 1.36 to 7.87, p = 0.01). A BRCA2 mutation was present in eight (1.42%) cases versus six (0.13%) controls (OR = 11.3, 95%CI 3.9 to 32.6, p < 0.0001). Three of the fifteen cases with BRCA1/2 mutations developed invasive ipsilateral or contralateral breast cancer, on average 6 years from the diagnosis of DCIS. There were no deaths reported among the 15 mutation carriers with DCIS. Conclusions: DCIS is a part of the hereditary breast/ovarian cancer syndrome caused by BRCA1/2 mutations. Women with DCIS should receive genetic counseling and testing for BRCA1/2 mutations. BRCA1/2 mutations may predispose women to a better DCIS prognosis, but further studies are needed.