Incidence of Merkel Cell Carcinoma Rising Sharply

During the last decade or more in the United States, there has been a sharp increase in the number of cases of Merkel cell carcinoma (MCC), a neuroendocrine skin cancer with high metastatic potential. Given that rates of MCC are strongly age-associated, an aging population may be driving this increase in incidence, according to the results of a study published in the Journal of the American Academy of Dermatology.

“The incidence of MCC is increasing and will likely continue to rise as the baby boomer population enters the higher-risk age groups for MCC,” wrote Kelly G. Paulson, MD, PhD, of Fred Hutchinson Cancer Research Center, and colleagues. “We estimate the rates will exceed 2,800 MCC cases/year in 2020 and 3,250 cases/year in 2025 in the United States.”

According to the study, the incidence of MCC has grown rapidly since the disease was first described in 1972, with incidence worldwide including in France, Sweden, Germany, China, and Australia.

“MCC particularly affects the elderly; MCC’s relationship with age is much more pronounced than melanoma or solid tumors’ relationship with age,” the researchers wrote. “This relationship is observed despite the fact that infection with Merkel cell polyomavirus often occurs before adulthood.”

Paulson and colleagues conducted this study to determine the incidence of MCC in the United States and to project the incidence through 2025. To do that, they used registry data from the SEER-18 Database, which contained 6,600 cases of MCC reported from 2000 to 2013.

While the standardized incidence rate of all solid cancers decreased from 2000 to 2013, the rate of aggressive skin cancer increased significantly. For all solid tumors, there was a 15.5% increase in the total number of cases reported to SEER-18. However, for melanoma there was a 56.5% increase and for MCC there was a 95.2% increase in reported cases. 

The researchers found that the incidence of MCC increased significantly with age. The incidence rate increased 10-fold between people 40 to 44 and 60 to 64 years of age, and then 10-fold again between people aged 60 to 64 years and those aged 85 and older.

The researchers combined this SEER data with US Census population data to estimate the total incidence of MCC in the US from 2000 to 2013, and to project the rates for 2015, 2020, and 2025. Assuming that incidence rates stay stable, the total incidence of MCC in 2020 is projected to be 2,835 cases per year, and is expected to increase to 3,284 cases per year by 2025.

“Because of its high propensity for spread, the need for adjuvant radiation in many cases, and the clear role for early immunotherapy in the metastatic setting, both early detection and optimal management will be critical for improved outcomes,” the researchers wrote. “These ongoing increases in MCC incidence strongly advocate for increased specialty appropriate MCC-specific education to the broad set of providers that care for MCC patients.”