The article summarizes the main mechanisms  underlying the radiosensitizing effect of photosensitizers.

According to literature data many authors  consider the formation of reactive oxygen species to be the key element  in the implementation of the antitumor  effect of ionizing radiation, which transfers the photosensitizer molecule from the ground  state to the excited state. Their formation leads to the development of oxidative stress. The consequence of the realization of the oxidative stress induced by ionizing radiation is apoptosis of tumor cells.

The first photosensitizers, which radiosensitizing  activity was confirmed, were hematoprofyrin and photophryn II. A detailed  analysis of the results of experimental  studies of radiosensitizing effect of photosensitizers on cell culture and laboratory animals with transplanted lines of malignant gliomas (glioma C6, gliosarcoma 9L, glioblastoma U87-MG) was made.

The method of tumor radiosensitizing by administration of photosensitizers has been tested in patients with recurrent gliomas grade III-IV in a number of oncological centers. The obtained results show its good tolerability and antitumor  efficacy.

We have not found publications  on the study of the radiosensitizing effect of chlorine-based photosensitizers in the available literature, that makes following studies in this field relevant.