Immunotherapy is developing as a therapeutic option for Merkel cell carcinoma; however, the long-term consequences on response, survival, and safety remain unknown. High-quality evidence is required to quantify this treatment’s efficacy and review the features of individuals and tumors that may enhance outcomes. For a study, researchers sought to provide an overview of the effectiveness and safety of immunotherapy in patients with Merkel cell cancer.

A systematic review of papers published in MEDLINE, Web of Science, Scopus, and EMBASE was conducted. Two reviewers independently assessed the literature and data extraction. The proportions for objective responses, progression-free survival, overall survival, and treatment-related adverse events were calculated. The relationships between objective response rate and immunobiologic markers were investigated.

About 6 clinical studies, including 201 immunotherapy patients, were included. The objective response rate was 51% (95% CI, 0.40-0.62; I2=37.1%), while grade ≥3 treatment-related adverse events occurred in 18% (95% CI, 0.11-0.29; I2=49.5%) of patients. There was no substantial difference in response rates and immunobiologic features.

Immunotherapy results in considerably decreased tumor dimensions, long-term response rates, and a safe profile. The fact that similar response rates were obtained on either subgroup of viral status or programmed death-ligand 1 expression implies that it may operate on several undiscovered mechanisms.