Comet assay is not useful to predict normal tissue response after radiochemotherapy in cervical and larynx cancer patients

Normal tissues reactions after radiotherapy vary considerably even between patients receiving the same treatment. The ability to predict the differences in radiosensitivity before radiotherapy would have important implication.

Patients with squamous cell carcinoma of the: (i) cervix (38 patients) and (ii) larynx (19 patients) were studied. Control group consisted of 9 healthy women. To assess individual radiosensitivity/chemoradiosensitivity alkaline version of comet assay was performed using isolated peripheral blood lymphocytes from cancer patients and healthy donors. The level of endogenous (0Gy), initial (immediately after 6Gy irradiation) and residual (after irradiation and 1h of repair) DNA damage was investigated.

The mean value of endogenous damage was similar in control and cervical cancer (CCU) groups and significantly lower than in larynx cancer patients. Cancer patients showed slower DNA repair. For CCU and larynx patients, comet assay parameters were not helpful for unequivocal prediction of appearance of acute and late radiation reaction effects.

Comet assay seems to be unable to predict normal tissue reaction after radiochemotherapy. Therefore, there is still need for developing predictive assays, however, due to complicated mechanism of chemoradiosensitivity, only assays assessing not one but many molecular pathways might gives us reliable score.