Long-term Tumor Control and Late Toxicity in Patients with Prostate Cancer Receiving Hypofractionated (2.2 Gy) Soft-tissue-matched Image-guided Intensity-modulated Radiotherapy

Aim: We report the long-term tumor control and toxicity outcomes of patients undergoing hypofractionated (2.2 Gy) image-guided intensity-modulated radiotherapy (IGIMRT) using tomotherapy for clinically localized prostate cancer. Patients and Methods: We examined the cases of 138 consecutive patients with stage T1-T3 prostate cancer that were treated with IG-IMRT from June 2007 to July 2009. The median follow-up time was 79 months (range=31-96 months). The planning target volume received a dose of 72.6-74.8 Gy in 33-34 fractions (2.2 Gy/fraction). Megavoltage computed tomographic (CT) scans were performed before each treatment and corrected to the registered positions on the planning CT scans using prostate soft-tissue matching. Results: The 5-year biochemical and clinical relapse-free survival rates were 95% for the low-risk group, 92% for the intermediate-risk group, and 77% for the high-risk group. The 5-year incidence rates of grade 2 and 3 late gastrointestinal toxicities were 6.3% and 3.1%, respectively, and those of grade 2 and 3 late genitourinary toxicities were 7.9% and 0%, respectively. Multivariate analysis indicated that T-stage is a prognostic factor for biochemical relapse-free survival rates. Conclusion: This report involved the longest followed-up cohort of patients to have received hypofractionated (2.2 Gy) soft tissue-matched IG-IMRT using tomotherapy. The findings of this study indicate that hypofractionated IMRT is well tolerated and is associated with good long-term tumor-control outcomes in patients with localized prostate cancer.