According to new research presented at the American Academy of Dermatology annual meeting last week, the incidence of Merkel cell carcinoma is rising[i]. Merkel cell cancers are a rare type of skin cancer that develops in Merkel cells, which are in the top layer of the skin[ii]. Though it is rare, Merkel cell carcinoma (MCC) is highly aggressive and often fatal[iii].
The researchers used data from the Surveillance, Epidemiology, and End Results Program (SEER-18) database, which contained 6,600 cases of MCC, to determine patterns of incidence of MCC between 2000 and 2013. They also made projections for future numbers of cases by combining this data with United States census data. During 2000-2013, the number of MCC cases increased by 95 %. For comparison, the number of solid cancer cases increased 15 % and the number of melanoma cases increased 57 %. In 2013, the incidence rate of MCC was 0.7 cases per 100,000 people per year, corresponding to 2,488 cases per year in the USA.
The incidence of MCC in the USA increases dramatically with age, increasing 10-fold from 0.1 to 1.0 cases per 100,000 per year between the 40-44 years and 60-64 years age groups, and then again to 9.8 cases per 100,000 per year in the 85 years and over age group. Due to the increasing numbers of older people, total incidence rates are predicted to increase to 3,284 cases per year by 2025.
According to Dr Paul Nghiem, one of the senior researchers, ‘Compared to melanoma, MCC is much more likely to be fatal, so it’s important for people to be aware of it’[iv]. Like other skin cancers, MCC is associated with cumulative exposure to ultraviolet radiation from the sun. It is also associated with a virus, known as the Merkel cell polyomavirus, which is common, though the vast majority of people exposed to the virus do not develop MCC. Those most likely to be affected by MCC are people with a prior history of skin cancer, men, Caucasians, and those aged over 50. Age is a particularly significant risk factor, and the ageing population is the main reason for the recent increases and predicted future increases in numbers of cases reported in this study.
[i] Paulson, K. G. et al. Merkel cell carcinoma: Current US incidence and projected increases based on changing demographics. Journal of the American Academy of Dermatology 78, 457–463.e2 (2018). http://www.jaad.org/article/S0190-9622(17)32585-9/fulltext (Accessed 22 February 2018)
[ii] Merkel cell skin cancer. Cancer Research UK. http://www.cancerresearchuk.org/about-cancer/neuroendocrine-tumours-nets/merkel-cell-skin-cancer (Accessed 22 February 2018)
[iii] American Academy of Dermatology. "Increasing incidence of rare skin cancer." ScienceDaily. ScienceDaily, 16 February 2018. www.sciencedaily.com/releases/2018/02/180216174658.htm. (Accessed 22 February 2018)