The risk of melanoma with rasagiline compared with other antiparkinsonian medications: A retrospective cohort study in the United States medicare database

PURPOSE: Compare the risk of melanoma between initiators of rasagiline or other antiparkinsonian drugs (APDs) in a Parkinson's disease (PD) population. METHODS: A retrospective cohort study was conducted in the US Medicare claims research database (2006–2015) in adults aged ≥65 years with PD claims. Other APD initiators were randomly matched (4:1) to rasagiline initiators on age, sex, and cohort entry year. Cutaneous melanoma events were identified by a validated claims algorithm. Incidence rates (IRs), incidence rate ratios (IRRs), and Cox‐adjusted hazard ratios (HRs) for melanoma comparing rasagiline with other APD initiators were calculated and analyzed by duration of study medication use and cumulative dose of rasagiline. Potential indicators of surveillance bias were explored. RESULTS: Among 23 708 rasagiline initiators and 96 552 matched APD initiators, the crude IR of melanoma/100 000 person‐years was 334.3 (95% confidence interval [CI], 291.5–381.6) and 208.2 (95% CI, 190.1–227.5), respectively (crude IRR 1.61; 95% CI, 1.36–1.89). The adjusted HR was 1.37 (95% CI, 1.14–1.65) and increased with longer rasagiline exposure and higher cumulative rasagiline doses. Rasagiline initiators more frequently had dermatologist visits or skin biopsies before cohort entry than APD initiators and had a higher incidence of nonmelanoma skin cancer during follow‐up (crude IRR, 1.44; 95% CI, 1.35–1.54). CONCLUSIONS: A small increased incidence of melanoma with exposure to rasagiline compared with other APDs was observed. Although the pattern with dose and duration is consistent with a hypothesized biologic effect, the increased skin cancer surveillance among rasagiline users suggests surveillance bias as a contributing explanation for the observed results.