A study conducted in Denmark and published in the journal Epidemiology contests the hypothesis that treatment of Parkinson disease increases the risk of melanoma.

Melanoma is a type of cancer that originates in cells of the skin. Melanoma is considered very deadly once it has spread past the site of origin. However, if melanoma is caught and treated prior to spread, cure rates are high. Typically, the treatment for melanoma that has not spread is surgical removal of the cancer and a surrounding area of healthy tissue.

Parkinson disease is a disorder of the brain that causes movement problems. Treatment of Parkinson disease may include the use of medications such as levodopa. While some reports have suggested that levodopa may be linked with an increased risk of melanoma, at least three reviews of the topic have concluded that the link was coincidental.

To further evaluate the relationship between Parkinson disease and melanoma, researchers in Denmark conducted a study to evaluate the frequency of melanoma prior to Parkinson disease. The researchers reasoned that if risk of melanoma was increased prior to Parkinson disease, as well as after, it would suggest that factors other than Parkinson disease treatment explain the higher risk of melanoma among patients with Parkinson disease.

The study involved more than 8.000 people with Parkinson disease and a comparison group of more than 32,000 people without Parkinson disease. Information about cancer diagnoses was collected from the Danish Cancer Registry.

  • A history of melanoma (prior to Parkinson disease diagnosis or a comparable date in the comparison subjects) was more common in patients with Parkinson disease than in the comparison subjects.
  • Patients with Parkinson disease were less likely to have a history of smoking-related cancers. This is consistent with the observation that risk of Parkinson disease appears to be higher in never-smokers than in former or current smokers.

Because the increased risk of melanoma among patients with Parkinson disease was apparent prior to the diagnosis of Parkinson disease, this study weakens the hypothesis that treatment of Parkinson disease increases the risk of melanoma.

Reference: Olsen JH, Friis S, Frederiksen K. Malignant Melanoma and Other Types of Cancer Preceding Parkinson Disease. Epidemiology. 2006;17:582-587.

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