Modeled Risk Of Radiation Induced Cancers After Prostate Cancer Radiation Treatment

Abstract

This study investigates into the second cancer risks to the bladder and rectum during Three-Dimensional Conformal Radiotherapy Treatment (3D-CRT) of prostate cancer compared to the baseline cancer risks in literature. The risk of induced-radiation cancer related with radiation treatment for patients with prostate cancer is of great importance in clinical radiation oncology. Therefore, the dose response relationship to predict radiation-induced secondary cancers was modeled for localised prostate cancer patients treated at Sweden Ghana Medical Centre (SGMC) over the past 5 years. Data of thirty patients’ who received a total dose of 78 Gy with 39 fractions during treatment were selected. Dose-volume histograms from pelvic planning CT scans were used to determine organ equivalent doses (OEDs) for bladder and rectum using linear dose response, linear-plateau and competition models. From BEIR VII risk models, the age-dependent lifetime attributable risks to organs inside the primary beam with a known tendency for cancer was estimated using organ equivalent doses obtained. The estimated risks of radiation-induced cancer for bladder and rectum were in the ranges of 1.17 %-4.4 %, 0.14 % - 0.28 % and 3.4E-06 % - 1.6 %, and 0.38 % - 2.17 %, 0.19 % - 0.63 % and 2.05E-09 % - 0.11 % for linear dose response, linear plateau and competition models respectively. The risk estimations by these models were observed to be similar as compared to the range of risks available in literature except for the linear dose response model. Results confirm that patients who are younger, are at higher risk of developing secondary cancer later in their life time compared to older patients. The ideal models were found to be linear-plateau and competition model at high doses.