Presentation (CTI)

OBJECTIVES: Merkel cell carcinoma (MCC) is a rare, aggressive carcinoma of cutaneous neuroendocrine cells, associated with a high risk of local recurrence and distant metastases. The current systematic literature review aims to understand the epidemiology of MCC across the United States (US).
METHODS: Electronic databases such as Embase® and Medline® were searched to identify relevant MCC studies reporting epidemiological data. US-specific, English language articles were included from the last 10 years. The standard Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) compliant two independent review and quality control process was followed during data collection.
RESULTS: Overall, 21 studies providing US-specific MCC epidemiological data were included. As per the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) database, the age-adjusted incidence rate (AIR) of MCC ranged from 0.40 per 100,000 person-years (PY) (2004-2015) to 0.68 per 100,000 PY (2013-2021). Incidence rates were consistently higher among men, with a two-fold increase in AIR from 0.55 to 1.04 per 100,000 PY between 1997-2021, whereas a modest increase was observed among women (0.28 to 0.46 per 100,000 PY) between 1997-2016. Over the period from 1988 to 2018, MCC mortality rates were higher in men compared to women, ranging from 29.44%-68.50% and 21.08%-31.50%, respectively. Overall mortality increased steadily from 0.03 to 0.43 per 100,000 PY between 1986 and 2011. Common risk factors for MCC included male sex, age ≥65 years, organ transplant recipients, and ultraviolet radiation exposure, whereas a lower risk was observed among non-white individuals.
CONCLUSIONS: This review highlights the rising incidence of MCC in the US, particularly among older adults, men and immunocompromised individuals. These trends underscore the need for improved surveillance and further research to guide prevention and treatment strategies.