Population differences in Merkel cell carcinoma by virus status and anatomic site: A multi-cohort analysis including institutional, SEER, and NCDB data

Merkelcell.org Summary

Merkel cell carcinoma (MCC) is a rare but serious skin cancer that can be caused either by ultraviolet radiation (UVR) from the sun and/or by a common virus called the Merkel cell polyomavirus (MCPyV). When MCC is caused by the virus, it is called “virus-positive.”

MCC is seen most often in White patients, so not much is known about how it affects people of different races and ethnicities.

This study explored whether the following three things are connected: where MCC first appears on the body, what causes MCC of particular body part (MCPyV or UVR), and a patient’s race or ethnicity. Using data from 695 MCC patients at the University of Washington, the researchers found that virus-positive MCC is linked to better survival, which matches what past studies have shown. Using data from 2,039 MCC patients at different institutions, they also found that Black and Hispanic patients were more likely to have MCC tumors in parts of the body that are not usually exposed to the sun. These tumors are often virus-positive, which is therefore linked to better outcomes.

Overall, this study helps us better understand how race, ethnicity, tumor location, and viral status may all relate to outcomes in MCC. It also helps us understand why Hispanic patients in the US with MCC have the highest survival rates. However, larger studies are needed using more patients across diverse racial groups.

Abstract

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

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

Methods: 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.

Results: 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.

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