UV Radiation and MCPyV Account for Most Merkel Cell Cases

TOPLINE:

Merkel cell polyomavirus (MCPyV) and ambient ultraviolet radiation (UVR) exposure account for most Merkel cell carcinoma (MCC) cases in the United States.

METHODOLOGY:

• Researchers evaluated 38,020 MCC cases (38% women; 93% non-Hispanic White, 4% Hispanic, 1% non-Hispanic Black) diagnosed in the United States from 2001 to 2019 to estimate the contribution of potentially modifiable risk factors to the burden of MCC.
• Population-based cancer registries and linkages with HIV and transplant registries were utilized to identify MCC cases in patients with HIV, solid organ transplant recipients, and patients with chronic lymphocytic leukemia (CLL).
• Data on cloud-adjusted daily ambient UVR irradiance were merged with cancer registry information on the county of residence at diagnosis to assess UVR exposure. Studies reporting the prevalence of MCPyV in MCC specimens collected in the United States were combined via a meta-analysis.
• The study assessed population attributable fractions of MCC cases that were attributable to major immunosuppressive conditions (HIV, solid organ transplant, and chronic CLL), ambient UVR exposure, and MCPyV.

TAKEAWAY:

• The incidence of MCC was higher in people with HIV (standardized incidence ratio [SIR], 2.78), organ transplant recipients (SIR, 13.1), and patients with CLL (SIR, 5.75) than in the general US population. However, only 2.5% of MCC cases were attributable to these immunosuppressive conditions.
• Non-Hispanic White individuals showed elevated MCC incidence at both lower and higher ambient UVR exposure levels, with incidence rate ratios of 4.05 and 4.91, respectively, for MCC on the head and neck.
• A meta-analysis of 19 case series revealed that 63.8% of MCC cases were attributable to MCPyV, with a similar prevalence observed between immunocompromised and immunocompetent patients.
• Overall, 65.1% of MCC cases were attributable to ambient UVR exposure, with higher attribution for cases diagnosed on the head and neck than those diagnosed on other sites (72.1% vs 60.2%).

IN PRACTICE:

“The results of this study suggest that most MCC cases in the US are attributable to MCPyV and/or ambient UVR [UV radiation] exposure, with a smaller fraction attributable to three major immunosuppressive conditions,” the authors wrote. “Future studies should investigate UVR mutational signature, TMB [tumor mutational burden], and MCPyV prevalence according to race and ethnicity and patient immune status to help clarify the overlap between MCC risk factors,” they added.

SOURCE:

The study was led by Jacob T. Tribble, BA, Division of Cancer Epidemiology and Genetics, National Cancer Institute (NCI), Rockville, Maryland. It was published online on November 27, 2024, in JAMA Dermatology.

LIMITATIONS:

Incidences of MCC may have been inflated because of increased medical surveillance in immunosuppressed populations. The analysis assumed that only cases among non-Hispanic White individuals were associated with UVR. Additionally, the meta-analysis of MCPyV prevalence primarily included studies from large academic institutions, which may not be representative of the entire US population.

DISCLOSURES:

This study was supported in part by the Intramural Research Program of the NCI and the National Institutes of Health Medical Research Scholars Program. Additional funding was provided through a public-private partnership with contributions from the American Association for Dental Research and the Colgate-Palmolive Company to the Foundation for the National Institutes of Health. The authors reported no relevant conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.