Abstract
Simple SummaryRecently, 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 Gy1.5 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 Gy1.5) and low-dose UHF (L-UHF; EQD2 ≤ 100 Gy1.5). 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 Gy1.5 is a feasible UHF schedule with a good balance between toxicity and efficacy.
Highlights
Prostate cancer became a major malignancy in developed countries [1]
We retrospectively examined 253 patients treated with ultrahypofractionation radiotherapy (UHF) [6] and 499 patients treated with dose-escalated radiotherapy (DeRT) [270 Uji-Takeda
The patient eligibility criteria were (1) patients treated with UHF or DeRT, (2) the clinical stage T1–T4 and N0M0 with histology-proven adenocarcinoma; the availability and accessibility of pretreatment data level, T classification, and the Gleason score sum (GS) to determine the stage according to the NCCN 2015 risk classification as follows: low (T1–T2a, GS 2–6, and iPSA < 10 ng/mL), intermediate (T2b–T2c, GS 7, or PSA 10–20 ng/mL), and high (T3–T4, GS 8–10, or PSA > 20 ng/mL) [1]
Summary
Prostate cancer became a major malignancy in developed countries [1]. As many curative treatment options exist, surgery, external beam radiotherapy, and brachytherapy, it is difficult to choose the best treatment option [2]. Recent advancements in radiotherapy for localized prostate cancer have enabled us to shorten the treatment period using hypofractionations and provide cost effectiveness and patient convenience. In the place of conventional 1.8–2-Gy fractionation, 2.3–3.4-Gy moderate hypofractionation has already become the standard of care [3]. The biological features of prostate cancer with a low α/β ratio encouraged the adoption of these hypofractionations and UHF worldwide [2,3]
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