Population differences in Merkel cell carcinoma by virus status and anatomic site: A multi-cohort analysis including...

The impact of race/ethnicity on Merkel cell carcinoma (MCC) outcomes remains inconclusive.

To examine associations between MCC primary site, virus status, environmental ultraviolet radiation (UVR), and race/ethnicity.

Patients diagnosed with MCC at the University of Washington (UW), in Surveillance, Epidemiology, and End Results (SEER-17), in National Cancer Database (NCDB), and global incidence and virus status data were included in this retrospective multi-cohort study. We estimated the prognostic effect of virus status using a Cox proportional hazards model, conducted a pooled analysis of tumor site and virus status, and investigated racial/ethnic differences in site using SEER and NCDB. We also estimated global MCC viral subtype incidences and assessed their association with geographic UV indices.

Virus-positive MCC (VP-MCC) showed improved survival compared to virus-negative MCC (VN-MCC) (P < .001) and was more likely to develop on UV-protected skin (P < .001). Black and Hispanic patient tumors were more likely to present on UV-protected sites (P < .001). Globally, UVR had a bigger effect on VN-MCC incidence than VP-MCC.

Nonstandardized virus assays, unknown patient migration histories, incomplete global data, and registry selection bias.

Black and Hispanic patients more often develop MCC on UV-protected sites, which are more likely VP-MCC and associated with improved outcomes.