Cancer risk in association with Parkinson disease : a population-based study

PURPOSE: Data from large population-based studies on the association between Parkinson disease (PD) and the risk of developing cancer are scarce. We compared the risk of developing incident cancer between patients with or without PD. METHODS: We conducted a population-based follow-up study and a nested case-control analysis using data from the UK-based General Practice Research Database. We included PD patients aged </=40 years with a first PD diagnosis between 1994 and 2005, and a matched comparison group free of PD. We assessed cancer incidence rates and relative risk estimates (odds ratios [ORs] with 95% confidence intervals [CI]). RESULTS: The risk of developing cancer overall was lower in PD patients as compared to patients without PD (crude incidence rate ratio 0.77, 95% CI 0.64-0.92). In the nested case-control analysis (adj. OR for all cancers 0.72, 95% CI 0.59-0.87) the risk reduction was strongest for smoking-related cancers (adj. OR 0.47, 95% CI 0.31-0.72). The adjusted OR for hematological malignancies was 0.32 (95% CI 0.14-0.74). Due to small numbers, ORs for other cancer entities did not reach statistical significance. CONCLUSIONS: With the exception of melanoma, PD patients were less likely to develop cancer than individuals without PD in this large observational study.