Secondary cancer risk assessment after high-risk and intermediate-risk prostate cancer radiotherapy in Senegal

Abstract

Purpose: This study aims at evaluating the excess absolute risk (EAR) of cancer in thirty patients with high and intermediate risks of prostate cancer based on the Amico’s classification, who received a three-dimensional conformal radiotherapy (3DCRT) or a modulated volumetric arc therapy (VMAT) with 6 MV photons energy. Materials and Methods: VMAT plans were performed in simultaneous integrated boost, with 76 Gy to prostate and 56 Gy to pelvic lymph node and seminal vesicle. 3DCRT planning was realized in two stages with prostate, seminal vesicles, and pelvic lymph node receiving 46 Gy, in the first stage, and in the second stage, prostate prescribed at 28 Gy. The EAR was assessed using the Schneider concept based on the equivalent dose for a given organ (OED). Thus, the EAR of the rectum, bladder, pelvic bone and healthy pelvic tissues were calculated and compared on the basis of the Mechanistic, Exponential Linear, Plateau and Sarcoma specific Mechanistic models. Results: The EAR in the rectum were found to be higher in 3DCRT than in VMAT. The EAR values ranged from 3.98-5.37 for the rectum, and from 1.05-3.76 for the bladder depending on the model used. Conclusion: The overall EARs analysis for both radiation modalities indicated that the risk of induction of carcinoma in the rectum was higher with 3DCRT, compared with VMAT. However, it would be necessary for validation of predicted models, to conduct prospective clinal trials with a larger patient cohort