Optimal Androgen Deprivation Therapy Combined with Proton Beam Therapy for Prostate Cancer: Results from a Multi-Institutional Study of the Japanese Radiation Oncology Study Group.

Androgen deprivation therapy (ADT) combined with radiation therapy benefits intermediate- and high-risk prostate cancer (PC) patients. The optimal ADT duration in combination with high-dose proton beam therapy (PBT) remains unknown.

Intermediate- and high-risk PC patients treated with PBT combined with ADT for various durations were analyzed retrospectively. To assess the relationship between ADT and biochemical relapse-free (bRF) rate, Cox proportional hazards models including T stage, prostate specific antigen (PSA) level, Gleason score (GS), and total radiation dose were used.

In the intermediate-risk PC patients (n = 520), ADT use improved bRF (HR 0.49, 95% CI 0.26-0.93; p = 0.029), especially in those with multiple intermediate-risk factors (T2b-2c, PSA 10-20 ng/mL, and GS 7). In the high-risk PC patients (n = 555), a longer ADT duration (>6 months) conferred a benefit for bRF (HR 0.54, 95% CI 0.32-0.90; p = 0.018), which was most apparent in patients with multiple high-risk factors (T3a-4, PSA > 20 ng/mL, and GS ≥ 8) treated with ADT for ≥21 months.

Short-term (≤6 months) ADT is beneficial for intermediate-risk PC patients, but likely unnecessary for those with a single risk factor, whereas ADT for >6 months is necessary for high-risk PC patients and ADT for ≥21 months might be optimal for those with multiple risk factors in combination of high-dose PBT.

Cancers. 2020 Jun 25*** epublish ***

Motohiro Murakami, Hitoshi Ishikawa, Shosei Shimizu, Hiromitsu Iwata, Tomoaki Okimoto, Masaru Takagi, Shigeyuki Murayama, Tetsuo Akimoto, Hitoshi Wada, Takeshi Arimura, Yoshitaka Sato, Masahiko Gosho, Katsumasa Nakamura, Hideyuki Sakurai

Department of Radiation Oncology, University of Tsukuba, Faculty of Medicine, Tsukuba, Ibaraki 305-8576, Japan., Department of Radiation Oncology, Nagoya Proton Therapy Center, Nagoya City West Medical Center, Nagoya, Aichi 462-8508, Japan., Department of Radiology, Hyogo Ion Beam Medical Center, Tatsuno, Hyogo 679-5165, Japan., Proton Therapy Division, Shizuoka Cancer Center Hospital, Nagaizumi, Shizuoka 411-8777, Japan., Division of Radiation Oncology and Particle Therapy, National Cancer Center Hospital East, Kashiwa, Chiba 277-0882, Japan., Department of Radiation Oncology, Southern TOHOKU Proton Therapy Center, Koriyama, Fukushima 963-8052, Japan., Medipolis Proton Therapy and Research Center, Ibusuki, Kagoshima 891-0304, Japan., Proton Therapy Center, Fukui Prefectural Hospital, Fukui, Fukui 910-8526, Japan., Department of Biostatistics, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8576, Japan., Department of Radiation Oncology, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka 431-3192, Japan.