A rapid radiosensitivity assay, based on the flow cytometric assessment of radiation-induced CD8 T-lymphocyte apoptosis (RILA), has been developed [7,8,9], and a prospective study found that a high RILA value was associated with less grade ≥2 late radiation-induced toxicities [10] in patients with miscellaneous cancers. This evidence concerns the gene CD8A and cancer.