Presentation Authors: Naoki Fujita*, Masaki Momota, Yuki Tobisawa, Tohru Yoneyama, Hayato Yamamoto, Atsushi Imai, Shingo Hatakeyama, Hirosaki, Japan, Hiroyuki Ito, Hachinohe, Japan, Takahiro Yoneyama, Yasuhiro Hashimoto, Hirosaki, Japan, Kazuaki Yoshikawa, Mutsu, Japan, Chikara Ohyama, Hirosaki, Japan
Introduction: Several studies reported the efficacy and feasibility of radiation therapy (RT) to the primary tumor in patients with metastatic prostate cancer. However, there is no study in patients with metastatic castration resistant prostate cancer (mCRPC). We hypothesized that RT to the prostate would improve overall survival (OS) in mCRPC patients. Therefore, the aim of the present study was to evaluate the efficacy and feasibility of RT to the primary tumor in patients with mCRPC.
Methods: A total of 87 patients with mCRPC were examined retrospectively. Patients were divided into two groups between patients with RT after CRPC diagnosis (RT group) and without RT (non-RT group). We compared oncological outcomes, including cancer-specific survival (CSS) and OS between two groups. We performed multivariate Cox regression analyses using inverse probability of treatment weighting (IPTW) method to evaluate the impact of RT on CSS and OS.
Results: Median age at CRPC diagnosis was 74 years, and median follow-up periods after CRPC diagnosis were 28 months in this cohort. Of the 87 patients, 28 (32%) were treated with RT to the primary tumor after CRPC diagnosis. Median time from CRPC diagnosis to RT initiation were 18 months. The rates of adverse events related with RT in any grade and â‰¥grade 3 were 60% and 20%, respectively. The median PSA decline rate for RT was 24%. Twelve (43%) patients experienced â‰¥30% PSA decline for RT. Although CSS tended to be higher in RT group, it was not significant (P = 0.089). OS was significantly higher in RT group (P = 0.015). In multivariate Cox regression analyses with IPTW model, although RT was not significantly associated with CSS (P = 0.076), it was significantly associated with OS (P = 0.011, HR 0.260).
Conclusions: RT might improve oncological outcomes even in patients with mCRPC. Our next study will identify the adequate candidates of RT in patients with mCRPC.