Immune Checkpoint Inhibitor with or without Radiotherapy in Melanoma Patients with Brain Metastases: A Systematic Review and Meta-Analysis

Abstract

Objective: Immune checkpoint inhibitor (ICI) therapy has shown activity against melanoma brain metastases. Recently, promising results have also been reported for ICI combination therapy and ICI combined with radiotherapy. We aimed to evaluate radiologic response and adverse event rates of these therapeutic options by a systematic review and meta-analysis.

Materials and methods: A systematic literature search of Ovid-MEDLINE and EMBASE was performed up to October 12, 2019 and included studies evaluating the intracranial objective response rates (ORRs) and/or disease control rates (DCRs) of ICI with or without radiotherapy for treating melanoma brain metastases. We also evaluated safety-associated outcomes.

Results: Eleven studies with 14 cohorts (3 with ICI combination therapy; 5 with ICI combined with radiotherapy; 6 with ICI monotherapy) were included. ICI combination therapy {pooled ORR, 53% (95% confidence interval [CI], 44-61%); DCR, 57% (95% CI, 49-66%)} and ICI combined with radiotherapy (pooled ORR, 42% [95% CI, 31-54%]; DCR, 85% [95% CI, 63-95%]) showed higher local efficacy compared to ICI monotherapy (pooled ORR, 15% [95% CI, 11-20%]; DCR, 26% [95% CI, 21-32%]). The grade 3 or 4 adverse event rate was significantly higher with ICI combination therapy (60%; 95% CI, 52-67%) compared to ICI monotherapy (11%; 95% CI, 8-17%) and ICI combined with radiotherapy (4%; 95% CI, 1-19%). Grade 3 or 4 central nervous system (CNS)-related adverse event rates were not different (9% in ICI combination therapy; 8% in ICI combined with radiotherapy; 5% in ICI monotherapy).

Conclusion: ICI combination therapy or ICI combined with radiotherapy showed better local efficacy than ICI monotherapy for treating melanoma brain metastasis. The grade 3 or 4 adverse event rate was highest with ICI combination therapy, and the CNS-related grade 3 or 4 event rate was similar. Prospective trials will be necessary to compare the efficacy of ICI combination therapy and ICI combined with radiotherapy.

Keywords: Immune checkpoint inhibitor; Immunotherapy; Meta-analysis; Radiation; Radiotherapy.

Fig. 1. Flow chart of the study selection process.

ICI = immune checkpoint inhibitor

Fig. 2. Forest plot of the intracranial (A) objective response rates and (B) disease control rates excluding symptomatic cohorts.

Intracranial objective response rate was significantly higher when using ICI combined with radiotherapy (42%; 95% CI, 31–54%) and ICI combination therapy (53%; 95% CI, 44–61%) compared to ICI monotherapy (15%; 95% CI, 11–20%). Intracranial disease control rate was also significantly higher when using ICI combined with radiotherapy (85%; 95% CI, 63–95%) and ICI combination therapy (57%; 95% CI, 49–66%) compared to ICI monotherapy (26%; 95% CI, 21–32%). CI = confidence interval