Planning study to optimize the dose for low-risk prostate cancer with two IMRT techniques

Abstract

Author(s): Moulay Ali Youssoufi, Mohammed Bougtib, Youssef Bouzekraoui*, Mohamed Ait Erraisee, Fatima Zahra Abboud, Souad Oubelkacem, Khalid Hassouni, Dissi Lalla btissam and Farida Bentayeb

Purpose: The aim of this work is a comparison study of the plan quality betwe en two techniques of a common Intensity Modulated Radiation Therapy (IMRT) was performed to optimize the dose for low risk prostate cancer. Materials and methods: Based on CT datasets of ten patients with prostate cancer treated at our institution were randomly selected for this study. To optimize the IMRT technique, Two IMRTs configurations, differing for gantry angle direction, were tested for each patient. The first technique (IMRT-S) was used as reference plan utilized a five beams configuration, standard for prostate cancer treatment in our institution, and the second technique (IMRT-OP) combining five plans with five beams for each (25 beams in total), changing beam directions every 7 sessions level (70Gy in 35 fractions) to be irradiated. Plan quality was evaluated by comparing Homogeneity Index (HI), Conformity Index (CI), monitor units (MUs) especially dose volume statistics of the Organs at Risk (OAR) from each technique. Results: For the same Planning Target Volume (PTV) coverage, the IMRT-OP plans show superior dose homogeneity and conformity in PTV compared to IMRT-S technique. Target coverage was almost similar for both techniques. The sparing of Rectum in terms of 70Gy dose was better in the IMRT-OP technique by 4.9% when compared to the IMRT-S technique. A considerable reduction in 65Gy dose to the Bladder by 3.4% was observed with the IMRT-OP. At the end Remarkable reduction of the dose received at the femoral heads between 36.31% and 53.30% always in favour of the IMRT-OP technique. Conclusion: Considering the superior quality of the IMRT-OP plan compared to IMRT-S, IMRT-OP may be the preferred modality for centres that don’t have VMAT technique for the treatment of prostate cancer, taking into account significant improvements in OAR.

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