RADIOBIOLOGICAL ANALYSIS OF DIFFERENT RADIATION REGIMENS IN PREOPERATIVE RADIATION THERAPY FOR COLON CANCER
This study presents the results of the analysis of relationships between time-dose-fractionation (TDF) factor values and parameters of tumor cell survival (TCS) and intestinal cell survival (ICS) for different dose-fractionation regimens in preoperative radiation therapy for colon cancer. The obtained data sug- gest that the hypothesis about the presence of a linear correlation between TDF values and decimal lo- garithm (DL) of TCS and ICS parameters cannot be rejected (p<0.05). Besides, significant linear regression (over 95 % significance) enables to approximate DL of TCS and ICS parameters depending on TDF values. The control regimen consisted of 2 Gy per daily fraction to a total tumor dose of 30 Gy. Furthermore, two variants of preoperative irradiation to a total tumor dose of 25 Gy and 18 Gy were compared. The TCS and ICS values obtained indicated that intensive preoperative irradiation to 25 Gy was superior to 18 Gy because radiation therapy given once a day to a total tumor dose of 25 Gy increa- sed tumor cells depletion by 130 times and radiation therapy given two times a day to a total tumor dose of 25 Gy increased tumor cells depletion by 18 times compared with the control regimen, whereas 18Gy radiation therapy increased tumor cells depletion only by 2.4 times.