Breast cancer in neurofibromatosis 1: survival and risk of contralateral breast cancer in a five country cohort study

PURPOSE: Neurofibromatosis 1 (NF1) is an autosomal dominant condition caused by pathogenic variants of the NF1 gene. A markedly increased risk of breast cancer is associated with NF1. We have determined the breast cancer survival and risk of contralateral breast cancer in NF1. METHODS: We included 142 women with NF1 and breast cancer from five cohorts in Europe and 335 women without NF1 screened for other familial breast cancers. Risk of contralateral breast cancer and death were assessed by Kaplan–Meier analysis with delayed entry. RESULTS: One hundred forty-two women with NF1 were diagnosed for breast cancer at a median age of 46.9 years (range 27.0–84.3 years) and then followed up for 1235 person-years (mean = 8.70 years). Twelve women had contralateral breast cancer with a rate of 10.5 per 1000 years. Cumulative risk for contralateral breast cancer was 26.5% in 20 years. Five and 10-year all-cause survival was 64.9% (95% confidence interval [CI] = 54.8–76.8) and 49.8% (95%CI = 39.3–63.0). Breast cancer–specific 10-year survival was 64.2% (95% CI = 53.5–77.0%) compared with 91.2% (95% CI = 87.3–95.2%) in the non-NF1 age-matched population at increased risk of breast cancer. CONCLUSION: Women with NF1 have a substantial contralateral breast cancer incidence and poor survival. Early start of breast cancer screening may be a way to improve the survival.