Radiobiological effect of different irradiation fractionated regimens in human brain glioma / 中华放射肿瘤学杂志

ABSTRACT

Objective To evaluate the radiobiological effect of different irradiation fractionated regimens in human glioma cells ( BT 325 cell line). Methods The xenografts in Balb/c-nude mice were irradiated with different single and fractionated regimens. The single fraction dose was 10, 20, 30, 40 and 60 Gy, respectively. The fractionated regimens were 2 Gy × 5 fractions ( irradiated every day), and 3 Gy ×3 fractions (irradiated every other day), 3 Gy × 5 fractions (irradiated every day) and 4 Gy × 3 fractions (irradiated every other day), with total doses of 125 Gy, 114 Gy, 126 Gy and 112 Gy, respectively. The growth curve was used to evaluate the tumor doubling time. clonogenic assays was performed to draw the cell survival curve and analyze the radiobiological parameters with doses of 1, 2, 4, 6, 8 and 10 Gy. T1/2 was measured by comet assay. Results Tumor regression were not observed by single fraction irradiation, 2 Gy × 5 fractons and 3 Gy × 3 fractions irradiation regimens. The tumor regress was more significant with the increas of fraction dose. The 4 Gy × 3 fractionrs inhibited tumor more though not curing tumor. The cell doubling time of the BT 325 cell was 30. 16 h and the tumor doubling time of the xenograft was 43 days.When fitted with L-Q model ,α was 0. 36 Gy -1 and β was 0. 057 Gy -2. When fitted with the single-hit multitarget model, D0 was 1. 394 Gy, Dq was 2. 127 Gy and SF2 was 0. 714, respectively. The T1/2 was 9. 999min. Conclusions Glioma is a radioresistant tumor. Increase of the fraction dose improves recent effect.Further study is needed to control the tumor stem cells.