Differential risks of cancer types in people with Parkinson's disease: a national record-linkage study

There is evidence that people with Parkinson's disease (PD) have a decreased risk of developing cancer. PD has also variably been shown to be associated with an increased risk of cancers like melanoma and breast. We investigated this relationship in a very large cohort of PD patients.

We constructed two cohorts of people from an all-England record-linked hospital and mortality dataset spanning 1999-2011. One cohort comprised people with a record of PD; the other comprised people without a record of PD. We 'followed up' these two cohorts to determine observed and expected numbers of people with subsequent primary cancers in each, based on person-years at risk, and calculated standardised rate ratios (RRs).

In 219,194 people with PD, the RR for all subsequent primary malignant cancers combined was 0.92 (95% confidence interval (CI) 0.91-0.93). Increased RRs (p<0.05) were found for six out of the 31 cancer types investigated, including breast, melanoma, uterus, kidney, and neurological malignancies. Decreased RRs were found for 11 cancer sites, including lung and colon cancer.

We corroborate the findings of a reduced risk for the development of cancers in PD patients shown in smaller studies, including cancers associated and not known to be associated with smoking; and of an increased risk of melanoma and breast cancer. To the best of our knowledge, this is the first study to report an association between PD and elevated rates of uterine and renal cancer. Further work is warranted to understand the mechanisms behind these findings.