Multicenter Retrospective Observational Research on the Outcome of Radical Radiation Therapy for Prostate Cancer with Metastases

Abstract

Hormonal therapy is the standard treatment for prostate cancer with metastases, but the disease usually becomes castration-resistant several years later. Before prostate cancer becomes castration-resistant, irradiating both the prostate and metastases may increase the local control rate and decrease the distant metastasis rate. In this multi-center study, we investigated clinical outcome and toxicities of patients with prostate cancer with metastases in patients irradiated as the first-line treatment (group A) in comparison with those irradiated after acquiring resistance to hormonal therapy (group B). Between January 2005 and June 2018, 91 patients with prostate cancer with 1-10 bone and/or 1-10 lymph node metastases were treated by IMRT. The prescription doses were 30-74.8 Gy to metastatic lesions and 60-78 Gy to the prostate. Among them, 13 patients were irradiated with IMRT and proton. Seventy-two patients only had lymph nodes, 11 had only bone metastases, and 8 had both metastases. Median age was 68 years (range, 54–85 years) and median follow-up was 32 months (range, 3-138 months). Seventy patients were in group A and 21 patients were in group B. Overall survival (OS) and progression free survival (PFS) at 3 years were 92% and 81%, respectively. At 3 years distant metastasis-free (DMF) rate were 82% in 73 patients and the local control rate of irradiated lymph nodes and bone metastases were 96% in 61 patients. Late Grade 2 or higher radiation genitourinary toxicities were seen in 2/91 and radiation gastrointestinal bleedings were observed in 4/91. No other Grade 2 or higher toxicities were seen. All genitourinary toxicities were Grade 2. At 3 years, OS was 95% versus 81%, PFS was 90% versus 51%, DMF rate was 90% versus 55% and the local control rate of irradiated lymph nodes and bone metastases was 100% versus 81% in groups A and B, respectively (log-rank P= 0.1, 0.00003, 0.002 and 0.009, respectively). The median of PSA doubling time (DT), which was calculated between the day of PSA nadir and the last follow-up date, was 5 months in 37 evaluable patients. The PSA failure was more frequently seen in the group with PSA DT < 10 months (n=20) than in the groups with stable PSA group (n=8) and with PSA DT ≥ 10 months (n=9) (P = 0.0017). To irradiate both the prostate and metastases before prostate cancer becomes castration-resistant may increase PFS, DMF, and the local control rate of irradiated lymph nodes and bone metastases from prostate cancer and decrease distant metastases rate.