Immunotherapy in patients with metastatic castration-resistant prostate cancer: a meta-analysis of data from 7 phase III studies and 3 phase II studies.

ABSTRACT

BACKGROUND: Immunotherapies have emerged as potential treatments for metastatic castration-resistant prostate cancer (mCRPC). However, it is still unclear to identify the efficacy and safety of immunotherapy in large-scale samples. We performed a meta-analysis of 7 phase III randomized trials and 3 phase II trials comparing immunotherapy to placebo in mCRPC. METHODS: Searching the PubMed, ClinicalTrials and Cochrane Library, completed III/IV phase trials were identified. Data extraction was conducted according to the PRISMA statement. The measured outcomes were OS, PFS, ORR and AE. Based on the results of phase III randomized trials, 3 II phase trials with results were identified. RESULTS: A total of 4185 patients were available for evaluation of OS, and 3320 for PFS. Compared to placebo, immunotherapies were not able to improve OS (HR = 0.90; 95%CI 0.79-1.03; p = 0.13). However, immunotherapies, especially ICBs were able to decrease the risk of progression over placebo by 18% (HR = 0.82; 95%CI 0.68-1.00; p = 0.04). Significant ORR improvement was found in patients treated in ICBs (RR = 1.90; 95%CI 1.30-2.78; p < 0.001). Immunotherapies (OR = 1.01, 95% CI = 0.40-2.56; OR = 1.27, 95% CI = 0.72-2.25) were not associated with significant any grade TRAEs and 3-4 grade TRAEs. However, in subgroup analysis, ICBs (OR = 2.85, 95% CI = 2.27-3.57) and vaccines (OR = 0.78, 95% CI = 0.64-0.53) were associated with significant 3-4 grade TRAEs respectively. Moreover, ICBs alone induced positive PSA response [OR = 2.43(1.09-5.43), P = 0.03(I2 = 0%, P = 0.83)] and was effective in advanced PC even without classical therapies based on three phase II clinical trials about ICBs. CONCLUSIONS: Immunotherapies are not able to improve OS, but significantly improve PFS and ORR especially in ICBs treatment. Immunotherapies were not associated with significant TRAEs. However, in subgroup analysis, ICBs and vaccines were associated with significant 3-4 grade TRAEs.