A Phase I/II Study of Ultra-Hypofractionated Carbon-ion Radiation therapy for Low- and Intermediate-Risk Localized Prostate Cancer

• Published in: Advances in radiation oncology 2025-03, Vol.10 (3), p.101705-101705, Article 101705
• Main Authors: Okonogi, Noriyuki, MD, PhD, Tsuji, Hiroshi, MD, PhD, Kobayashi, Kana, MD, PhD, Nakajima, Mio, MD, PhD, Aoki, Shuri, MD, PhD, Utsumi, Takanobu, MD, PhD, Suzuki, Hiroyoshi, MD, PhD, Akakura, Koichiro, MD, PhD, Ichikawa, Tomohiko, MD, PhD, Ishikawa, Hitoshi, MD, PhD
• Format: Article
• Language: English
• Subjects: Hematology, Oncology, and Palliative Medicine; Scientific
• ISSN: 2452-1094; 2452-1094
• DOI: 10.1016/j.adro.2024.101705

PurposeWe report herein the 3-year results of a phase I/II prospective study of 4-fraction course of carbon-ion radiation therapy (CIRT) in patients with localized prostate cancer. Methods and MaterialsThe present was a single-institution, phase I/II prospective study including patients with low- or intermediate-risk prostate cancer, as defined by the National Comprehensive Cancer Network criteria. Eligible patients were randomly assigned (1:1) to a 1- or 2-week schedule. Dose-limiting toxicities (DLTs) were defined as any genitourinary (GU) or gastrointestinal (GI) toxicity grade 3 or higher within 90 days of beginning CIRT. Ten patients were enrolled in each group, and the CIRT dose was increased in a stepwise manner if there were fewer than 4 cases of DLT. The initial CIRT dose was 36 Gy, followed by 40 Gy or 44 Gy. Low-risk patients did not receive androgen deprivation therapy (ADT), whereas intermediate-risk patients received 4 to 8 months of neoadjuvant ADT. ResultsBetween October 2018 and October 2020, 60 patients were enrolled in the present study and completed the treatment regimen. The median post-CIRT follow-up period was 42 months (range, 27-59 months). Of the 60 patients enrolled, 10 were in the low-risk group, and 50 were in the intermediate-risk group. Neither group experienced grade 3 or higher GI or GU adverse events; therefore, no dose-limiting toxicities were observed. The incidence of grade 2 GU toxicity within 90 days post CIRT was significantly higher in the 44 Gy group than in the 36 to 40 Gy group ( P < .01, chi-square test with Yates correction). Biochemical failure was observed in 3 cases by 3 years post CIRT. No clinical recurrence or death because of prostate cancer occurred. ConclusionsForty Gy in 4 fractions of CIRT may be appropriate for balancing the therapeutic effects and toxicity. Our findings support further investigations into the efficacy of this strategy.