Quantitative estimation of recovery parameters after combined action of ionizing radiation and chemical agents

The combined action of ionizing radiation with various chemical agents is often used to enhance the inactivation effect of tumor cells in cancer treatment. The enhancing effect seems to be accountable by direct chemical toxicity, cell recovery inhibition or the higher probability to produce primary radiation damage without changing the recovery process (1–4). Repair of DNA, as re lected in rejoining of strand breaks, may be of relevance to the cell recovery from sub lethal and potentially lethal damage (2, 5). Preferential impairment of DNA repair in malignant cells would be of great relevance in improving cancer treatment. The inhibition of cell recovery (2, 3, 6, 7) and DNA single and double strand breaks repair (8–11) by chemicals is expressed both as a deceleration of recovery rate and a lesser extent of recovery. It is obvious that the inhibition of cell recovery may be caused by the following reasons: (i) the damage or impairment of the recovery process itself, (ii) the increase in the portion of irreversible damage, and (iii) both these reasons may took place simultaneously. V.G. Petin1, J.K. Kim2*, E.S. Evstratova1, L.N. Komarova1