AACR 2025: What Role Do Potentially Modifiable Risk Factors Play in the Burden of MCC?

By: JNCCN 360 Staff
Posted: Thursday, May 29, 2025

In a recent study presented at the 2025 AACR Annual Meeting, Jacob T. Tribble, MD, of the National Cancer Institute, and colleagues looked at major potentially modifiable risk factors including immunosuppression, ultraviolet radiation (UVR) and infection with Merkel cell polyomavirus (MCV) to determine their estimated population attributable fractions for Merkel cell carcinoma (MCC) cases in the United States. Their findings highlighted that while immunosuppression caused only a small proportion of cases of MCC in the study’s patient population, UVR and MCV played a major role on MCC incidence.

The study authors calculated the population attributable fractions (PAFs) for patients from U.S. cancer registries in the HIV/AIDS Cancer Match Study, Transplant Cancer Match Study, and the Surveillance Epidemiology and End Results (SEER) Program data in order to determine the proportion of MCC cases tied to immunosuppression. SEER data was also used to calculate population quintiles of UVR exposure, while a meta-analysis of U.S. studies reporting on MCV was conducted to determine the viruses’ prevalence in MCC tissues. The study period was from 2001–2020; over 40,000 cases of MCC were included.

Compared to the general U.S. population, invesitgators found that organ transplant recipients had a 13 times higher risk MCC, and people with HIV had a 3 times higher risk. However, due to the rarity of exposure, only 0.2% and 1.7% of U.S. MCC cases were attributable to organ transplantation and HIV, respectively. The incidence risk rate for the various quintiles of UVR exposure were highest for the head and neck—between 4.24 and 5.03, with an overall PAF of 65.8%. Meanwhile, 66.1% of MCC cases were found to be attributable to MCV, according to the meta-analysis.

The study authors highlighted the need for future research to assess these risk factors’ combined impact, but concluded that UVR and MCV were the dominant contributors to disease burden.

Disclosures: The study authors reported no conflicts of interest.

AACR 2025