Kazuya Takeda - Department of Radiation Oncology, Tohoku University Graduate School of Medicine, Sendai, Japan
Yoshihide Kawasaki - Department of Urology, Tohoku University Graduate School of Medicine, Sendai, Japan
Toru Sakayauchi - Department of Radiation Oncology, Osaki Citizen Hospital, Osaki, Japan
Chiaki Takahashi - Department of Radiation Oncology, Iwate Prefectural Isawa Hospital, Oshu, Japan
Yu Katagiri - Department of Radiation Oncology, Japanese Red Cross Ishinomaki Hospital, Ishinomaki, Japan
Takaya Tanabe - Department of Radiation Oncology, Tohoku Rosai Hospital, Sendai, Japan
Yojiro Ishikawa - Department of Radiation Oncology, Tohoku Medical and Pharmaceutical University Hospital, Sendai, Japan
Keisuke Fujimoto - Department of Radiation Oncology, Iwaki City Medical Center, Iwaki, Japan
Masaki Kubozono - Department of Radiation Oncology, Miyagi Cancer Center, Natori, Japan
Maiko Kozumi - Department of Radiation Oncology, Miyagi Cancer Center, Natori, Japan
Keiko Abe - Department of Radiation Oncology, Iwate Prefectural Iwai Hospital, Ichinoseki, Japan
Kakutaro Narazaki - Department of Radiation Oncology, Sendai Medical Center, Sendai, Japan
Shun Tasaka - Department of Radiation Oncology, Sendai Medical Center, Sendai, Japan
Rei Umezawa - Department of Radiation Oncology, South Miyagi Medical Center, Ogawara , Japan
Takaya Yamamoto - Department of Radiation Oncology, South Miyagi Medical Center, Ogawara , Japan
Noriyoshi Takahashi - Department of Radiation Oncology, South Miyagi Medical Center, Ogawara , Japan
Yu Suzuki - Department of Radiation Oncology, South Miyagi Medical Center, Ogawara , Japan
Keita Kishida - Department of Radiation Oncology, South Miyagi Medical Center, Ogawara , Japan
So Omata - Department of Radiation Oncology, South Miyagi Medical Center, Ogawara , Japan
Akihiro Ito - Department of Urology, Tohoku University Graduate School of Medicine, Sendai, Japan
Keiichi Jingu - Department of Radiation Oncology, South Miyagi Medical Center, Ogawara , Japan

Objective(s): In the treatment of castration-resistant prostate cancer (CRPC) with bone metastases, radium-۲۲۳ dichloride (Ra-۲۲۳) is the only bone-targeted drug that shows survival benefits. Completing six courses of Ra-۲۲۳ treatment is thought to be associated with better patient survival, but this treatment has a relatively high rate of acute adverse events. Methods: This retrospective study included ۸۵ patients from ۱۲ institutions in Japan to investigate the clinical significance of the completion of Ra-۲۲۳ treatment and acute adverse events in CRPC patients. Results: Six courses of Ra-۲۲۳ treatment were completed in ۶۵.۹% of the patients. Grade ۳ or higher acute adverse events were observed in ۲۷.۱% of patients. The prostate specific antigen and alkaline phosphatase declined at ۲۶.۹% and ۸۷.۹%, respectively. The overall survival rates at ۱۲ and ۲۴ months were ۸۰.۷% and ۶۳.۲%, respectively. Both completion of six courses of Ra-۲۲۳ treatment and absence of grade ۳ or higher acute adverse events were associated with longer overall survival. In univariate analysis, factors related to the history of treatment (five or more hormone therapy agents and cytotoxic chemotherapy) and hematological parameters (Prostate specific antigen (PSA) doubling time, alkaline phosphatase, hemoglobin, albumin, and serum calcium) were associated with completing six courses of Ra-۲۲۳ treatment without experiencing grade ۳ or higher acute adverse events. Multivariate analysis showed that a history of chemotherapy, PSA doubling time, hemoglobin, and serum calcium showed statistical significance. We built a predictive score by these four factors. Patients with lower scores showed higher rates of treatment success (p<۰.۰۰۱) and longer overall survival (p<۰.۰۰۱) with statistical significance. Conclusions: Accomplishing six courses of Ra-۲۲۳ treatment without grade ۳ or higher acute adverse events was a prognostic factor in patients with mCRPC treated with Ra-۲۲۳. We built a predictive score of treatment success and need future external validation.

radium-۲۲۳ dichloride, Bone metastasis, castration-resistant prostate cancer, radioisotope therapy