Parkinson’s disease patients have a significantly higher risk of developing melanoma, and the opposite is also true, according to a new study. But researchers aren’t sure of the cause.
The study, “Parkinson Disease and Melanoma: Confirming and Reexamining an Association,” was published in the journal Mayo Clinic Proceedings.
Research dating back to 1972 has examined the correlation between the development of Parkinson’s disease and the incidence of melanoma. Many researchers have attributed the higher rates of melanoma in Parkinson’s patients to the drug levodopa, which is commonly prescribed in Parkinson’s disease. Other researchers have suggested a link between Parkinson’s and melanoma without the use of levodopa.
Overall, scientists have not been able to come to a consensus on whether the association is real, and if so, whether it is caused by levodopa.
Researchers at the Mayo Clinic in Rochester, Minnesota, made use of the Rochester Epidemiology Project (REP) medical records of patients from Olmsted County, Minnesota, as a way to obtain a large cohort of patients. They used data from the REP to review the charts of all available Parkinson’s patients and compared the incidence of melanoma to age- and gender-matched controls.
They also examined data on patients who had been diagnosed with conjunctival or uveal melanoma — two forms of eye cancer — and determined how many of them developed Parkinson’s.
Results from this study show that patients with Parkinson’s disease are 3.8-times more likely to have pre-existing melanoma compared to the control group. They also determined that patients with melanoma have a 4.2-times higher risk of developing Parkinson’s. Additional analyses revealed a 35-year cumulative risk of developing Parkinson’s disease in patients with melanoma.
Interestingly, patients with melanoma who did not develop Parkinson’s had a 10.5-fold increased risk of death due to metastatic melanoma compared to patients who have melanoma and Parkinson’s disease, indicating a potential protective effect.
Results from this study suggest a link between Parkinson’s disease and melanoma, but do not support levodopa as the cause.
The researchers note that despite the need for additional research on this topic, physicians treating either disease should stay cognizant of the other disease and monitor signs of development.
“Future research should focus on identifying common genes, immune responses and environmental exposures that may link these two diseases,” the study’s first author, Lauren Dalvin, MD, said in a release. “If we can pinpoint the cause of the association between Parkinson’s disease and melanoma, we will be better able to counsel patients and families about their risk of developing one disease in the setting of the other.”