Analysis of Hip Joint Dose in Prostate Cancer Radiation Therapy: A Dosimetric Comparison of Treatment Plans

Background and purpose: Radiation therapy as a part of cancer treatment is used in almost 50-60% of involved cases. In prostate cancer radiation therapy, a large volume of pelvis is irradiated, so, it is necessary to preserve sensitive organs around the treatment area, especially rectum and bladder. In this study, some dosimetric parameters such as minimum dose (Dmin), maximum dose (Dmax), mean dose (Dmean) to target (PTV) and organs at risk (OAR), Integral dose, Homogeneity Index and Conformity Index were compared between two techniques. Materials and methods: In this analytical study, computed tomography scans of 50 patients (mean age: 52 years) attending Sari Imam Khomeini Hospital were acquired and transferred to the 3D treatment planning system (TPS). For each patient, a conventional plan (Box Fields) and modified oblique four-field (MOFF) plan were prepared using TPS for 15 MV photon energy. A total dose of 7200 cGy was prescribed for each patient. Data analysis was carried out in SPSS applying paired-t-test. Results: In current study, 15-MV energies for radiation of pelvis and bladder using box radiation fields (routine plan) lead to maximum uniformity and homogeneity of dose in irradiated tumor tissue. The results also showed that 15-MV energies for radiation of pelvis and bladder and the new plan could decrease the average integrated dose in femur heads. Conclusion: We observed a significant effect of the geometrics of radiation fields on distribution of dose in tumor tissue and also the amount of dose received by organs at risk in radiotherapy of patients with prostate cancer.