Toxicity in combination immune checkpoint inhibitor and radiation therapy: a systematic review and meta-analysis

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Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology


BACKGROUND AND PURPOSE: Immune checkpoint inhibitor with radiation therapy (ICI + RT) is under investigation for improved patient outcome, so we performed a systematic review/meta-analysis of toxicities for ICI + RT compared to immune checkpoint inhibitor (ICI) therapy alone.

MATERIALS AND METHODS: A PRISMA-compliant systematic review of studies in MEDLINE (PubMed) and in the National Comprehensive Cancer Network guidelines was conducted, with primary outcome grade 3+ toxicity. Criteria for ICI alone were: phase III/IV trials that compared immunotherapy to placebo, chemotherapy, or alternative immunotherapy; and for ICI + RT: prospective/retrospective studies with an arm treated with ICI + RT. Meta-analysis was performed by random effects models using the DerSimonian and Laird method. The I(2) statistic and Cochran's Q test were used to assess heterogeneity, while funnel plots and Egger's test assessed publication bias.

RESULTS: This meta-analysis included 51 studies (n=15,398), with 35 ICI alone (n=13,956) and 16 ICI + RT studies (n=1,442). Our models showed comparable grade 3-4 toxicities in ICI + RT (17.8%; 95% CI, 12.0-24.5%) and ICI alone (22.3%; 95% CI, 18.1-26.9%). Stratification by timing of radiation and irradiated site showed no significant differences, but anti-CTLA4 therapy and melanoma showed increased toxicity. The grade 5 toxicities were 1.1% and 1.9% for ICI alone and ICI + RT respectively. There was significant heterogeneity, but not publication bias.

CONCLUSIONS: The random effects model showed comparable grade 3-4 toxicity in using ICI + RT compared to ICI alone in CNS melanoma metastases, NSCLC, and prostate cancer. ICI + RT is safe for future clinical trials in these cancers.

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ePub ahead of print