ABSTRACT

Radiobiological effects depend greatly on the nature of the tissue in question and how the physical dose is received which is defined by the treatment time (T), dose rate (D), and fractionation scheme (F). Time dose fractionation (TDF) determines the radio biological effective dose (BED). The BED should be in the optimum range for better disease-free survival (DFS). In this study, 100 patients were treated with conventional fractionation regime in arm 1 and equal number of patients treated with the hyperfractionation regime in arm 2. With the patient’s regular follow-up, the 5-year DFS were studied by analyzing the BED values of each patient. In arm 1, the patients were treated with parallel opposing fields in the head & neck region. In each field 90 or 100 cGy 102doses were given so that 180 or 200 cGy doses were delivered at the center of the tumor. All patients were treated 5 days per week for 6 weeks continuously. In arm 2, the doses delivered were 110 cGy in the morning and after a gap of 6 h again the same scheduled is followed. The treatment went on 5 days per week and a total of 33 treatment days. Chemotherapy agent cisplatin was administered to these patients once weekly to sensitize the tumor to radiation therapy. In both the regimes, BED was calculated for tumor (BEDta), normal cell early reactions (BEDne), and normal cell late reactions (BEDnl). The patients 5-year DFS were studied for both the regimes against the BEDta, BEDne and BEDnl. Five-year DFS in arm 1 was 9% whereas in arm 2 it was 24%. In both the regimes, 33% patients had more than 5-year DFS. The optimum BED can give better DFS, which can be achieved by the hyperfractionation regime.