Study of robust of dose distribution of prostate cancer before carbon ion treatment based on in-room CT / 中华放射肿瘤学杂志

ABSTRACT

Objective:To analyze the robustness of the dose of clinical target volume (CTV) and tolerance dose of normal tissues after applying in-room CT before carbon ion radiotherapy for prostate cancer.Methods:Thirty prostate cancer patients treated with carbon ion in Shanghai Proton and Heavy Ion Center from January 2020 to June 2021 were enrolled in this study. Five in-room CT images of each patient were selected randomly before treatment. Dose distributions were recalculated using the original plan on in-room CT images and dose volume histogram (DVH) parameters were obtained, including V 95% and V 90% of CTV and V 80% of rectum. The values were compared with the dosimetric parameters of the original plan. Statistical analysis was performed by paired or two independent samples t-tests. Results:The dose distribution was recalculated by applying in-room CT. The mean values of V 95% and V 90% of CTV and V 80% of rectum were 98.1%±1.2% ( P<0.001), 99.9%±0.2% ( P=0.001) and (5.8±1.6) ml ( P<0.001), respectively. The differences were statistically significant compared with those of the original plan. The frequency of V 95%≥95%, V 90%≥98% of CTV, and V 80%<10 ml of rectum was 148 (98.7%), 150 (100.0%) and 147 (98.0%), respectively. Conclusion:Based on in-room CT analysis and the patient management and positioning methods of our research center, the uncertainty of target dose and normal tissue dose in the entire process of prostate cancer carbon ion therapy is small, and the robustness is good.