Merkel cell carcinoma (MCC) is a rare and highly aggressive neuroendocrine skin cancer, which in some people is associated with a virus Merkel cell polyomavirus (MCV). The presence of high levels of antibodies against MCV virus have been reported to be associated with better clinical outcomes, however, despite the antibodies, MCC usually spreads or metastasizes. The prevalence of antibodies to MCV is around 85% in the general population, meaning that the vast majority of people with MCV never get MCC.  Thus, only a slight percentage of those infected with MCV develop MCC, suggesting that other factors govern its development.

If you have MCC, but it has not metastasized yet, you have an expected 80% chance of five year survival.  However, with metastasized MCC included, there is an overall 5-year survival rate of about 60% for all MCC combined. One problem is that up to half of patients who have been seemingly treated successfully subsequently suffer a recurrence of their disease.

There are roughly 1,500 new cases of MCC diagnosed each year in the United States, compared to around 60,000 new cases of melanoma. Immune suppression can profoundly increase the odds of developing Merkel cell carcinoma. For example, Markel cell carcinoma occurs 12 times more often in people with advanced HIV as compared to the general population. The incidence of MCC in the US is increasing rapidly for unknown reasons.

Lesions usually appear purple-red in color and there is little else to distinguish this variant of skin cancer from other types. Its identity usually comes as a surprise after dermatological excisional surgery and pathologic examination. Surgery is usually the first treatment that a patient undergoes for Merkel cell cancer. Radiotherapy is also commonly used to treat Merkel cell cancers.

Dr M. Samimi and colleagues of Tours France decided to see if vitamin D deficiency was associated with tumor characteristics and prognosis in MCC.

Samimi M et al. Vitamin D deficiency is associated with greater tumor size and poorer outcome in Merkel cell carcinoma patients. J Eur Acad Dermatol Venereol. 2013 Feb 1.

Here is what they found:

• 25(OH)D Levels of less than 20 ng/ml were noted in 65% of the 89 patients studied and was independently associated with greater tumor size at diagnosis (P = 0.006) and with metastasis recurrence (P = 0.043).
• 25(OH)D was not associated with death from MCC, although there was a trend (P = 0.093) in favor of fewer deaths in vitamin D sufficient patients.
• The vitamin D receptor (VDR) was detected in all MCC samples, indicating the MCC tumors had not destroyed the VDR as some other cancers do.

The authors wrote,

“In conclusion, this study suggests poorer prognosis in MCC patients with vitamin D deficiency, with increased tumor size at presentation and poorer clinical outcome. The VDR is expressed in MCC tumors and the active metabolite of vitamin D, 1,25 di-hydroxy-vitamin D, might influence MCC biology. Larger prospective studies are necessary to confirm a link between vitamin D status and MCC characteristics and prognosis.”