Comparing Cancer Risk Management between Females with Truncating 1100delC versus Missense I157T Variants.

Breast cancer (BC) risks imparted by c.1100delC ("1100delC") germline pathogenic/likely pathogenic variant (GPV) are 20-30%, compared to c.470T>C ("I157T") GPV with <20%, leading to different breast screening recommendations through MRI. We compared cancer risk management (CRM) across these two GPVs. Study participants were adult females with an 1100delC or I157T GPV drawn from the Inherited Cancer Registry (ICARE) across the United States. Cancer history, clinical characteristics, and CRM were compared using chi-squared tests, t-tests, and logistic regression. Of 150 carriers, 40.7% had BC, with a mean age of 50. Comparing 1100delC and I157T GPVs, there were no differences in rates of (1) breast MRI among those with (65.2% versus 55.6% of 23 and 9; = 0.612) and without (44.0% versus 44.8% of 50 and 29; = 0.943) BC; (2) risk-reducing mastectomy among those with (50% versus 38.9% of 46 and 15; = 0.501) and without (13.8% versus 6.5% of 58 and 31; = 0.296) BC; and (3) risk-reducing salpingo-oophorectomy among those with (24.2% versus 22.2% of 45 and 18; = 0.852) and without (17.5% versus 16.7% of 57 and 30; = 0.918) BC. The results suggest over-screening with breast MRI among I157T GPV carriers and possible overuse of risk-reducing surgeries among carriers.