The clinical value of adding immune checkpoint inhibitors to radiotherapy for cancer: a systematic review and meta-analysis.

While several randomized clinical trials (RCTs) have explored the addition of immune checkpoint inhibitor (ICI) treatment for patients undergoing radiotherapy, studies systematically assessing the clinical value of such interventions are lacking. PubMed, Embase, and Cochrane Library databases were searched for relevant RCTs of cancers that received ICIs plus radiotherapy or radiotherapy. Eligible studies were those published in English as of 14 April 2024. Two independent reviewers screened the included studies and extracted relevant data, then selected the random or fixed-effects model based on the I2 statistic. The main outcomes were hazard ratios (HRs) with 95% confidence intervals (CIs) for overall survival (OS) and progression-free survival (PFS); Odds ratios (ORs) with 95% CIs for objective response rate (ORR), disease control rate (DCR), and adverse events (AEs). Stratified analysis was performed based on cancer type, ICI type, and the timing of ICI addition. The study was registered on PROSPERO (CRD42024551008). 15 RCTs with 7947 patients were included. Pooled HRs were 0.865 (95% CI, 0.730-1.000; I2 = 72.1%) for OS and 0.799 (0.677-0.922; I2 = 82.0%) for PFS in cancer patients. In cancer types, adding immunotherapy to radiotherapy significantly improved patients with non-small-cell lung cancer (OS: 0.544 [0.371-0.717]; PFS: 0.527 [0.438-0.617]) and cervical cancer (OS: 0.722 [0.578-0.867] and PFS: 0.754 [95%CI, 0.621-0.887]). Regarding the ICIs schedule, adjuvant ICI therapy with pooled HRs was 0.742 (0.649-0.834) for OS and 0.638 (0.579-0.697) for PFS. In addition, the pooled ORs for the incidence of grade 3 or higher treatment-related and immune-related adverse events were 1.227 (1.059-1.421; I2 = 71.9%) and 2.217 (1.743-2.821; I2 = 74.0%), respectively. Adding immunotherapy to radiotherapy can provide significant clinical benefits for patients with NSCLC and cervical cancer, and the addition of these ICIs in the adjuvant stage is supported.