INTRODUCTION We examined the prevalence of cancer in patients with Parkinson’s disease (PD) and controls evaluated at the Mayo Clinic Florida between 2003 and 2014. METHODS We retrospectively collected information regarding cancer diagnoses and diagnosis of PD in a total of 971 unrelated PD patients and 478 controls, and all were white. For PD patients, we examined cancers diagnosed before and after PD diagnosis separately in addition to considering all cancer diagnoses. RESULTS Twenty different cancers were identified. In PD patients, the most common types of cancer were skin cancer (17.3% overall; 10.6% before PD), followed by nonmelanoma skin cancer (16.0% overall; 9.7% before PD), prostate cancer in men (12.8% overall; 9.2% before PD), breast cancer in women (10.6% overall; 6.3% before PD), and melanoma (2.4% overall; 1.1% before PD). Compared to controls, a significantly lower frequency of nonmelanoma skin cancer (odds ratio [OR]: 0.62, P=0.0024) and any skin cancer (OR: 0.57, P=0.0002) was observed in PD patients. These differences were greater when considering only cases with cancers that occurred before PD diagnosis (OR: 0.49, P<0.0001; OR: 0.45, P<0.0001, respectively), and there was a lower frequency of melanoma and any cancer preceding PD diagnosis compared to controls (OR: 0.31, P=0.003; OR: 0.36, P<0.0001). There was no evidence of a frequency difference for any other cancer. CONCLUSIONS PD patients had a lower frequency of skin cancers or any cancer prior to PD diagnosis compared to controls, suggesting that cancer may have a protective effect on PD risk.

We retrospectively investigated the co-occurrence of Crohn's disease in a cohort of 876 patients with Parkinson's disease, based on the observation that LRRK2 is a shared genetic risk factor. We identified 2 patients with Crohn's disease; this number was consistent with the number of cases expected in the general population.

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