Prognosis of Breast Cancer in Carriers of BRCA1 and BRCA2 Mutations

To the Editor: Rennert et al. (July 12 issue)¹ report that a BRCA1 or BRCA2 mutation was not a significant predictor of mortality from breast cancer in an Israeli population-based cohort. However, 43% of potential cases were not included because tumor samples or medical records could not be retrieved, and excluded cases were more likely than included cases to be fatal. If BRCA1 carriers have more aggressive tumors,² leading to earlier death, this could result in a spuriously improved prognosis (Neyman bias). In addition, the investigators did not study tumor grade (associated with mutation status),³ nor did they identify prognostic . . .