Optimizing the schedules of fractionated irradiation in subclinical tumors of malignant glioma / 中华放射肿瘤学杂志

ABSTRACT

Objective To study dose-response relationship and screen the optimized fractionated irradiation schedules in subclinical tumors of malignant glioma.Methods Balb/c-nude mice bearing human malignant glioma xenograft were assigned randomly into control group,fractionated irradiation schedules group and nimotuzumab-conventional fraction group.The fractionated schedules were 200 cGy x 5f/w,300 cGy ×5f/w,160 cGy ×2f/d x5 d and 400 cGy ×3f/w with total dose of 40 Gy and 60 Gy,respectively.Measurement indexes were tumor-forming rate,average recurrence time and maximum diameter of the tumor bottom.The observation lasted 24 weeks.Results With the total dose of 40 Gy,none of the significant long-term tumor regression were detected in any fractionated irradiation schedules; 400 cGy x 3f/w with complete tumor response at the end of treatment showed a better short-term curative effect.With the total dose of 60 Gy,long-term control rate of each fractionated irradiation schedule group was improved with prolonged average recurrence time of varable degrees,except 200 cGy x 5f/w fractionated schedule (tumor formation rate was 100％ at the end of treatment and average recurrence time was the poorest of 108 d).160 cGy × 2f/d × 5 d fractionated schedule showed the best curative effect with no tumor formation in 2 of 8 mice and longest recurrence time of 143 d.300 cGy x 5f/w fractionated schedule ranked second with no tumor formation in 1 of 8 mice and average recurrence time was 137 d.400 cGy x 3f/w fractionated schedule produced the poorest outcome with no case cured.There were no significant changes in the tumor-forming rate or average recurrence time when nimotuzumab was concurrently used for subclinical tumors of malignant glioma with total dose of 60 Gy.Conclusions Conventional fractionated irradiation is not the best option to control the sustained growth.160 cGy ×2f/d ×5 d and 300 cGy × 5f/w might be the optimized fractionated irradiation schedules for subclinical tumors of malignant glioma.