Efficacy of immune checkpoint inhibition in metastatic uveal melanoma: a systematic review and meta-analysis.

Metastatic uveal melanoma (mUM) has historically been associated with short survival and limited effective treatments. Immune checkpoint inhibitors (ICIs) have been trialed in mUM; however, robust conclusions regarding their efficacy are difficult to draw given small study sizes and heterogeneous patient populations. Five databases were searched using a combination of 'ICI' and 'mUM' headings, and data on patient demographics, objective response rate (ORR), overall survival (OS) and progression-free survival (PFS) were extracted. Pooled ORR was calculated using a random effects model and the inverse variance method. Available Kaplan-Meier OS and PFS curves were used to construct summary OS and PFS plots, from which median values were derived. Pooled ORR was 9.2% overall (95% CI 7.2-11.8) [4.1% for anti-CTLA4 (95% CI 2.1-7.7), 7.1% for anti-PD(L)1 (95% CI 4.5-10.9) and 13.5% for anti-CTLA4 plus anti-PD1 (95% CI 10.0-18.0)]. Median OS was 11.5 months overall (95% CI 9.5-13.8) [8.0 months for anti-CTLA4 (95% CI 5.5-9.9), 11.7 months for anti-PD(L)1 (95% CI 9.0-14.0) and 16.0 months for ipilimumab plus anti-PD1 (95% CI 11.5-17.7) ( P < 0.001)]. Median PFS was 3.0 months overall (95% CI 2.9-3.1). ICIs have limited efficacy in mUM and a recommendation for their use must consider the balance of benefit and risk for individual patients if no other options are available. Further biomarker profiling studies may be helpful in assessing which patients will benefit from ICIs, in particular the addition of ipilimumab to anti-PD1 therapy.