Abstract 234P
Background
While the referral criteria are established in suspicion of genetic predisposition to invasive breast cancer (IBC), there are currently no guidelines on genetic testing for breast ductal carcinoma in situ (DCIS). A few papers described a 3.2 to 29.2% BRCA1 and BRCA2 pathogenic variants (PV) yield in DCIS. Moreover, little is known about the subsequent IBC risk in PV carriers.
Methods
Since 2000, DCIS has been considered equivalent to IBC as a referral criterium for genetic testing in our center. Women with pure DCIS who have been referred to our genetic clinic between 01/01/2000 and 31/12/2019 and who underwent germline testing for breast cancer genes as an index case (including at least BRCA1 and BRCA2) were included in the present analysis. Exclusion criteria included personal history of other malignancy. We collected clinical characteristics and outcomes from medical files.
Results
Out of 9736 female index cases who underwent germline breast cancer predisposing genes testing over the period, 178 had pure DCIS. Of them, 5 (2,8%) and 11 (6,2%) had a PV in BRCA1 or BRCA2, respectively. TP53 and PALB2 VP rates were 5,2% (4/59) and 2,5% of tested women (2/79). Medium age at diagnosis was significantly lower in patients with a PV than those without (41,9 versus 47 years (p=0,042). Family history of ovarian cancer, but not of breast cancer, in first or second degree relatives, was associated with identification of a PV (p<0,01 and p=0,16, respectively). Pathological characteristics of DCIS were not associated with the probability of PV. Prophylactic contralateral mastectomy was performed in 43% of the PV carriers and only in 3,2% of cases in the WT group.
Conclusions
In our study, applying IBC genetic testing criteria to DCIS was effective with a 12% VP yield, but, interestingly, family history of breast cancer did not seem predictive of VP identification. No histological feature was associated with identification of a PV.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Gustave Roussy.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.