Clinical Impact of Immunotherapy in Merkel Cell Carcinoma patients: a Systematic Review and Meta-Analysis
Background: Merkel cell carcinoma (MCC) is an aggressive tumor with high mortality and increasing incidence rates, especially in the aging population. Current evidence regarding the immunotherapy’s effect on clinical response and safety is controversial. Objective: To summarize immunotherapy’s effect on the confirmed overall response, as well as its safety in patients with MCC. Methods: A generalized linear-mixed model analyzed objective responses, progression free survival, overall survival, and treatment-related adverse events (TRAE) for meta-analysis of proportions. We calculated the mean reduction and standard deviation for each individual tumor diameter. Objective responses comparing Merkel cell polyomavirus serology status were analyzed using odds ratio through a fixed-effects model. Results: Six clinical trials involving 201 patients treated with immunotherapy were included. Confirmed objective response rate was 51% (95%CI, 0.40-0.62; I2=37.1%). Although TRAE of any grade were observed in 84% (95%CI, 0.64-0.94; I2=79.4%), grade ≥ 3 was observed in 18% (95%CI, 0.11-0.29; I2=49.5%). Conclusions: The included agents offer good response rates with significant reduced tumor diameter. They were well tolerated, offering an alternative for patients who are refractory to conventional treatment. Agents studied here may be considered ahead of those recommended by the NCCN guidelines and drugs approved by the FDA.