Impact of Radiotherapy on Prognosis in Patients Diagnosed with Metastatic Prostate Cancer: A Systematic Review and Meta-Analysis

Abstract

<b><i>Background:</i></b> It has been reported that compared with no local therapy (NLT), patients treated with local therapy (LT) using radiotherapy (RT) possess higher survival rate in metastatic prostate cancer (mPCa). The aim of this meta-analysis was to evaluate the impact of RT on prognosis in patients with mPCa. <b><i>Methods:</i></b> We retrieved the literature in PubMed, Embase, and Cochrane Library databases until June 2019 using structured search terms. Several studies were included, which evaluated patients with mPCa who received RT versus NLT. <b><i>Results:</i></b> A total of 14,542 patients were analyzed in 7 included papers (2 randomized controlled trials [RCTs] and 5 cohort retrospective studies [CRS]), and 2,232 mPCa patients were treated with RT and 12,310 with NLT. The data of RCTs and CRS were analyzed separately. In RCTs, RT was associated with no significant difference in overall survival (OS) (pooled hazard ratio [HR] = 0.96; 95% confidence interval [CI]: 0.85–1.09; <i>p</i> = 0.55; <i>I</i>² = 42%) relative to NLT, while survival benefit was observed in the low-metastatic burden group (pooled HR = 0.68; 95% CI: 0.54–0.86; <i>p</i> = 0.001; <i>I</i>² = 0%), and no survival benefit was observed in the high-metastatic burden group (pooled HR = 1.07; 95% CI: 0.92–1.24; <i>p</i> = 0.39; <i>I</i>² = 0%). In CRS, RT results in lower cancer-specific mortality (CSM) (pooled HR = 0.49; 95% CI: 0.34–0.75; <i>p</i> &#x3c; 0.00001; <i>I</i>² = 0%) and higher OS (pooled HR = 0.61; 95% CI: 0.55–0.68; <i>p</i> &#x3c; 0.00001; <i>I</i>² = 0%) relative to NLT. Subsequent analysis demonstrated that high level of M-stage or N-stage was associated with increased CSM (pooled HR = 2.08; 95% CI: 1.69–2.55; <i>p</i> &#x3c; 0.00001; <i>I</i>² = 0% and pooled HR = 1.16; 95% CI: 1.03–1.30; <i>p</i> &#x3c; 0.00001; <i>I</i>² = 0%; respectively). <b><i>Conclusions:</i></b> Our observations in aggregate indicated that RT at least does not appear to be harmful and may be beneficial for low-metastatic burden patients and better condition patients. More prospective and randomized studies evaluating RT for mPCa are warranted.