Postirradiation Apoptosis of Peripheral Blood Lymphocytes as a Marker of Individual Radiosensitivity: a Mini-Review
Radiotherapy is a commonly used modality for cancer treatment. Despite its effectiveness, radiation therapy has been associated with complications due to the undesirable radiation exposure of surrounding normal organs and tissues. The optimal way to minimize this problem is to identify patients who are prone to late radiation injury. Over the years, a variety of techniques has been designed to measure individual radiosensitivity, including cell-based assays. One such promising approach exploits the radiation sensitivity of human periphe-ral blood lymphocytes (PBLs), in particular, postirradiation apoptotic changes in these cells. An increasing number of reports demonstrates a significant inverse correlation between the radiation-induced apoptosis rate in specific subpopulations of PBLs and the risk and severity of radiotherapy late toxicity in patients with different cancers. Although little is known about the mechanism(s) underlying such relationship, a recent prospective multicenter study has confirmed a powerful negative-predictive value of high apoptotic rate in <i>ex vivo</i> irradiated CD8<sup>+</sup> T lymphocytes for late fibrosis occurrence following radiotherapy. The review discloses the methodology for flow cytometric assessment of the radiation-induced apoptosis in PBLs of cancer patients focusing on the modifications of this functional assay used in different laboratories. The prospects for clinical application of this technique aimed at the individualization of radiotherapy are discussed.