A recent study from Archives of Neurology suggests that those with Parkinson’s disease (PD) may be at a higher risk for both melanoma and prostate cancer. The paper also found that people with these cancers may also share a higher risk for developing PD.

The reported link between melanoma (a form of skin cancer) and PD is not new. For years, researchers have speculated on whether the higher risk for melanoma is based on having Parkinson’s disease itself, or if it results as a side effect of taking levodopa, the gold standard therapy for the disease. The Michael J. Fox Foundation (MJFF) has funded researchers to further investigate this connection: One such study is searching to find out if an increased expression of the protein alpha-synuclein might be the culprit.

In a 2010 interview with MJFF, Susan Bressman, MD, chairman of the department of neurology at Beth Israel Medical Center, explained why levodopa might make someone more likely to develop melanoma:

Levodopa is needed to make the skin pigment melanin. So it makes sense that if you introduce excess levodopa into the system or hype up the system in any way, you could increase risk for melanoma. The usual precaution a neurologist would take for a patient with a history of melanoma is to be cautious about treatment with dopaminergics…

Adds Foundation staffer Maurizio Facheris, MD, MSc: “Subjects who have had melanoma in the past need to have very frequent dermatologic visits if they take levodopa, as the drug could cause their melanoma to reoccur.

Still, according to Bressman, recent studies have found that the risk for melanoma is not from taking the dopaminergic drugs but, instead, from having Parkinson’s. While the jury is still out on what exactly is causing the link between PD and melanoma, it is clear that Parkinson’s patients and their clinicians should be vigilant in checking for skin cancer.

The recent Archives of Neurology paper also found that men with PD and their male relatives had an elevated risk for prostate cancer. Since prostate cancer is by definition a male-only disease, says Facheris, and since PD is more prevalent in men, this study could help to drive attention to the shared underlying disease mechanisms between certain forms of cancer and Parkinson’s. A better understanding of what’s taking place in the body in both diseases could lead to new insights into therapeutic targets for drug developers.