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Parkinson's disease, not levodopa, linked to melanoma
Buenos Aires - Levodopa therapy for Parkinson's disease (PD) does not have any causal link to cutaneous malignant melanoma, a systematic review of published evidence shows.
However, there is "good evidence" of an excess risk of melanoma in patients with PD, which could be related to "a common genetic profile or a confounding role of social class", Italian and Argentine researchers report in the June issue of the journal Melanoma Research.
The investigators note in their paper that "since the early 1970s, a number of case reports have suggested that levodopa therapy for Parkinson's disease increases the risk of cutaneous malignant melanoma." It was hypothesized that levodopa could trigger or activate melanoma by sharing the biosynthetic pathway of melanin.
To investigate further, the team analyzed 36 published case reports and case-control studies as well as one Danish prospective cohort study.
They conclude that a causal association is "substantially inconsistent".
"Taking into account the evidence-based medicine, neurologists should not limit the use of levodopa in patients with a history of melanoma," co-author Dr. Dora Loria, of the University of Buenos Aires' Roffo Institute, Argentina, told Reuters Health.
On the other hand, the incidence of melanoma does appear to be higher in patients with PD, but the researchers attribute the link to a common genetic vulnerability or a "confounding role of social class".
For instance, the team notes that there is a proven inverse relationship between smoking and both melanoma and PD, "which could be a reasonable alternative explanation (to the causal association hypothesis)," Dr. Loria said.