Thirteen-year Retrospective Study of Radiation Toxicities Correlation with Dosimetry Factors V70 for Prostate Cancer in a Community Cancer Center

Summary: For prostate cancer radiation treatment, there are some contradictions between intense modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) in sparing the rectum and bladder. In this retrospective study, we explore these contradictions while evaluating radiation therapy's short and long-term side effects on prostate cancer patients and the correlation with dosimetry factors, especially at the rectum and bladder doses of 5000 cGy (V50) and 7000 cGy (V70). We compared V50 and V70 treated with VMAT vs. IMRT to a total dose of 75.6Gy, respectively, for whole pelvic radiotherapy (WPRT), which includes the prostate, seminal vesicles, and pelvic nodes, and for a total treatment in prostate-only radiotherapy (PORT) Patients with prostate cancer were treated in a clinical community setting between 2010 and 2023. PSA levels, GS scores, dose-volume histogram (DVH) results, consultations, and follow-up visits are all compared. Treatment plans were completed using Pinnacle Treatment Planning System (TPS, Philips Medical). A total of 123 prostate cancer patients were treated with radiation, with 36% experiencing adverse effects. 67% of those adverse effects were toxicity grades G>2. Comparing V70 dosimetry values presents valuable information for treatment planning, clinical outcomes, and toxicities. When focusing on PORT, the average V70 values for the bladder and rectum with VMAT were 20.75 and 10.5, respectively, compared to 22.74 and 12.97 for IMRT. For WPRT, VMAT had average V70 values of 25.5 and 16.2, respectively, compared to IMRT, which had average V70 values of 21.16 and 15.15, respectively. For patients with toxicity grades G>2, average V70 values for the bladder and rectum with PORT IMRT treatment were 22.6 and 11.5, respectively, as compared with 23.8 and 15.03 for WPRT IMRT treatment. Grade 2 toxicity has not been reported in VMAT treatment patients. Comparing V50 gives a pattern similar to that of V70 . When focusing on PORT, the average V50 values for the bladder and rectum with VMAT were 34.5 and 23.8, respectively, compared to 37.95 and 26.7 for IMRT. For WPRT, VMAT had average V70 values of 58.58 and 54.5, respectively, compared to IMRT, which had average V70 values of 46.57 and 43.61, respectively. According to our observations, VMAT and IMRT are compatible in the treatment of prostate cancer. When comparing the V50 and V70 values of VMAT and IMRT, VMAT presented better when it came to PORT, whereas IMRT presented better when it came to WPRT. In addition, VMAT presents with faster and smoother delivery compared to IMRT, which guarantees the intended planning dose. Considering the long- and short-term rectal and bladder toxicities, as well as the dose to organs at risk, VMAT may be the preferred treatment technique for prostate cancer patients. morteza dowlatshahi (he/him/his), MD DABR FACRO (Presenting Author) - Cancer Care Institute; Ly Do, MD (Co-Author) - Cancer Care Institute; Charlene Tan, PHD (Co-Author) - Cancer Care Institute; Hannah Garcia, BS (Co-Author) - Cancer Care Institute