A NEW study has found that 65.1% of Merkel cell carcinoma (MCC) cases in the US are attributable to ambient ultraviolet (UV) radiation exposure, 63.8% to Merkel cell polyomavirus (MCPyV), and only 2.5% to immunosuppressive conditions, such as HIV, solid organ transplants, and chronic lymphocytic leukaemia (CLL).
MCC is a rare but aggressive form of skin cancer, and understanding its risk factors is essential to inform preventative strategies. This study aimed to quantify the proportion of MCC cases attributable to modifiable risk factors, including UV radiation exposure and MCPyV prevalence, as well as immunosuppressive conditions, by analysing data from population-based cancer registries and case series.
Researchers analysed 38,020 MCC cases diagnosed between 2001 and 2019 in the US. MCC incidence was significantly higher among individuals with immunosuppressive conditions, with standardised incidence ratios of 2.78 for people with HIV, 13.1 for organ transplant recipients, and 5.75 for CLL patients. However, these conditions accounted for only 2.5% of MCC cases (0.2% due to HIV, 1.5% to organ transplant, and 0.8% to CLL). Conversely, 65.1% of MCC cases were attributed to UV radiation exposure based on geographic UV exposure data, with incidence rates particularly elevated among non-Hispanic White individuals in high and low UV exposure regions. A meta-analysis of 19 case series estimated that MCPyV accounted for 63.8% of MCC cases.
The findings underscore the dominant role of UV radiation and MCPyV in MCC development, with immunosuppressive conditions playing a minor role. In clinical practice, these results suggest that prevention efforts should prioritise reducing UV exposure through sun-protective behaviours, as MCPyV is widespread, and developing a vaccine for it is currently impractical. Future research should explore innovative prevention strategies, particularly for populations at high risk of UV-induced cancers.
Reference
Tribble JT et al. Merkel Cell carcinoma and immunosuppression, U radiation, and merkel cell polyomavirus. JAMA Dermatol. 2024;DOI:10.1001/jamadermatol.2024.4607.
