Ultrahypofractionated Radiotherapy versus Conventional to Moderate Hypofractionated Radiotherapy for Clinically Localized Prostate Cancer

Simple Summary Recently, shortening treatment time is becoming more important. Ultrahypofractionated radiotherapy (UHF) for localized prostate cancer is a fascinating treatment strategy; however, the concept of a well-balanced, optimal dose during UHF radiotherapy remains a contentious strategy, with only a few studies on UHF already reported. We must wait for the results of randomized trials several years away. Therefore, we tried to reveal the acceptable schedule in comparison to conventional to moderate hypofractionated radiotherapy so far. We found that UHF using EQD2 <= 100 Gy(1.5) is a feasible UHF schedule with a good balance between toxicity and efficacy. The purpose of this study was to compare the toxicity (first endpoint) and efficacy (second endpoint) of ultrahypofractionated radiotherapy (UHF) and dose-escalated conventional to moderate hypofractionated radiotherapy (DeRT) for clinically localized prostate cancer. We compared 253 patients treated with UHF and 499 patients treated with DeRT using multi-institutional retrospective data. To analyze toxicity, we divided UHF into High-dose UHF (H-UHF; equivalent doses of 2 Gy per fraction: EQD2 > 100 Gy(1.5)) and low-dose UHF (L-UHF; EQD2 <= 100 Gy(1.5)). In toxicity, H-UHF elevated for 3 years accumulated late gastrointestinal and genitourinary toxicity grade >= 2 (11.1% and 9.3%) more than L-UHF (3% and 1.2%) and DeRT (3.1% and 4.8%, p = 0.00126 and p = 0.00549). With median follow-up periods of 32.0 and 61.7 months, the actuarial 3-year biochemical failure-free survival rates were 100% (100% and 100% in the L-UHF and H-UHF) and 96.3% in the low-risk group, 96.5% (97.1% and 95.6%) and 94.9% in the intermediate-risk group, and 93.7% (100% and 94.6%) and 91.7% in the high-risk group in the UHF and DeRT groups, respectively. UHF showed equivocal efficacy, although not conclusive but suggestive due to a short follow-up period of UHF. L-UHF using EQD2 <= 100 Gy(1.5) is a feasible UHF schedule with a good balance between toxicity and efficacy.