Increased incidence of Merkel cell carcinoma among younger statin users

Statins (HMG-CoA-reductase inhibitors) are suggested to act as a predisposing factor for autoimmune diseases, have immunomodulatory effects, and possibly prevent some cancer types - the sum of these effects is unknown in cancers of viral aetiology, such as Merkel cell carcinoma (MCC). Aim of our study was to find out whether statin users in Finland have an increased incidence of MCC.

A cohort of 224715 male and 230220 female statin users during 1994-2007 was identified from the Prescription Register of the National Social Insurance Institution. This cohort was followed up through the Finnish Cancer Registry for MCC up to 2009.

There were altogether 50 cases of MCCs, while the expected number of cases, calculated on the basis of the MCC incidence in comparable Finnish population, was 39.9 (SIR 1.25, 95% CI 0.93-1.65). The standardized incidence ratio (SIR) for MCC in ages <60 years was 3.16 (95% CI 0.65-9.23), in ages 60-74 years 1.94 (95% CI 1.23-2.90) and in ages ≥75 years 0.89 (95% CI 0.57-1.31). The relative risk of MCC decreased significantly, 0.79 fold (95% CI 0.67-0.92), at each 5 year step when moving towards older age groups. There was no significant variation in SIR related to years since starting the statin use, or between the genders.

MCC is the first neuroendocrine cancer linked to statin use. The association is statistically significant and biologically plausible through immunomodulatory effects of statins. The excess of MCCs was observed in atypically young patients, a similar phenomenon as noted earlier in patients with immunocompromising states.