[en] Heterozygous mutations in BRCA1 or BRCA2 (breast cancer)have been found to be associated with enhanced cellular radiosensitivity with impaired proliferative capacity after irradiation and could predispose increased risk of radiation-induced mutagenesis and carcinogenesis (1,2). Deficient repair mechanism exhibited by lymphocytes from breast cancer patients provides associated vulnerability to genotoxicity of ionizing radiation. Other genes ay also play a role in terms o clinical radiation hypersensitivity needed in predicting response to radiotherapy. However, relaxation of cell cycle checkpoints, production of micronuclei, and loss of proliferative capacity which have been exhibited by impairment of irradiated cells lacking functional BRCA1 and BRCA2, accentuate the notion that heterozygous women may respond differently to radiation. The radioactive protein truncation test (PTT), utilized as screening procedures to detect frameshift mutations, can be employed to clarify radiosensitivity of individuals carrying a mutated BRCA1 gene. It can therefore, be incorporated in the series of clinical assays used in standard screening protocols for prospective nuclear facility workers. (author)