Immunotherapy is emerging as an alternative for Merkel cell carcinoma (MCC), but its long-term effects on response, survival, and safety are not well established. High-quality evidence is needed to estimate efficacy of this treatment and to review the characteristics of patients and tumor that might improve these outcomes.To summarize immunotherapy's efficacy and safety in MCC patients.A systematic review was performed for studies published in MEDLINE, Web of Science, Scopus, and EMBASE. Two reviewers reviewed the literature and data extraction in duplicate. We estimated the proportions for objective responses, progression free survival, overall survival, and treatment-related adverse events (TRAE). Associations between objective response rate (ORR) and immunobiological markers were analyzed.Six clinical trials of 201 patients treated with immunotherapy were included. The ORR was 51% (95% CI, 0.40-0.62; I2=37.1%), and grade ≥ 3 TRAE were observed in 18% (95% CI, 0.11-0.29; I2=49.5%) of patients. We observed no significant difference between response rates and immunobiological characteristics.A significantly reduced tumor diameter with durable response rates and a safe profile are obtained with immunotherapy. Similar response rates achieved on either subgroup of viral status or PDL-1 expression suggests that it might act on multiple, unexplored pathways.
Valeria F Garza-Davila, J Valdespino-Valdes, Francisco J Barrera, J Ocampo-Candiani, V Garza-Rodríguez