Dosimetric comparison of plans with and without flattening filter using volumetric modulated arc therapy technique using two different photon energies in prostate cancer patients undergoing early stage curative radiotherapy

Background and Aim: As with many types of cancer, radiotherapy is one of the most commonly used methods in the treatment of prostate cancer. With advances in technology, significant progress has been made in the radiotherapy techniques used in the treatment of prostate cancer. The aim of this study is to compare plans created using 6 and 10 MV photon beams with and without flattening filters (FF and FFF), respectively, using the Volumetric Modulated Arc Therapy (VMAT) technique, one of the latest technological advancements. Material and Methods: Twenty patients diagnosed with localised prostate cancer were included in our study. For each patient, VMAT treatment techniques were applied using the Varian Eclipse TPS system with the same contouring and optimisation values, and four different plans were created for each patient. Thus, dose data were obtained from a total of 80 plans. The plans were compared in terms of target volume (PTV) coverage, plan quality indices, doses delivered to organs at risk (OAR), and treatment application parameters. Results: Four different treatment plans were generated using 6 MV FF, 6 MV FFF, 10 MV FF, and 10 MV FFF energies with the VMAT technique. Based on the analysis results, the treatment plan created with 10 MV FFF energy was found to be statistically significantly superior compared to all other plans. According to the findings, the 10 MV FFF plan provided adequate dosimetric coverage of the target volume and offered more effective dose sparing for surrounding healthy tissues such as the bladder, rectum, urethra, and the right and left femoral heads. Conclusion: In a study conducted on patients with prostate cancer, it was concluded that the treatment plan created using 10 MV FFF energy with the VMAT technique could be an optimal option in terms of both tumor control and healthy tissue sparing.