by Caroline Cassels, Medscape, 23 Oct 2006
Patients with Parkinson's disease (PD) have a more than 2-fold increased risk of developing malignant melanoma compared with the general population, a new study has found.
Here at the American Neurological Association (ANA) 131st Annual Meeting, researchers from Creighton University in Omaha, Nebraska presented results of a large multicenter study that included 2106 patients from 31 movement-disorder centers across North America.
This data confirms the association between PD and skin cancer and tells us PD patients are at least twice as likely — and possibly up to 10 times as likely — to develop malignant melanoma. The reason for this is unclear, but these results certainly indicate the need for increased screening and prevention strategies in these patients," principal investigator John Bertoni, MD, told Medscape.
To establish the prevalence of melanoma, other skin cancers, and premalignant lesions, study subjects with confirmed idiopathic PD underwent prospective screening, which included a neurological examination to obtain demographic information, medical history, and current medication use.
Individuals were also screened by a dermatologist to determine melanoma risk factors and dermatologic history. All subjects also underwent whole-body dermatologic exams and biopsy of any suspicious skin lesions.
Biopsy specimens were evaluated by a central dermatopathology laboratory for melanoma, squamous and basal cell carcinomas, and other neoplasms.
This data was then compared with 2 national databases — the Surveillance Epidemiology and End Results (SEER), a database of US cancer statistics, and the American Academy of Dermatology (AAD) skin cancer screening programs.
Approximately 20% of study subjects had suspicious lesions. Among these, there were 24 cases of malignant melanoma — 24 in situ and 4 invasive. In addition, 117 basal cell and 28 squamous cell carcinomas were diagnosed.
Prevalence of invasive melanoma in US PD patients was 2.2-fold higher than in age- and sex-matched populations in the national SEER database. Compared with the AAD screening programs, the age- and sex-adjusted prevalence rate was between 8.3 and 10.6 times higher, respectively, than that found in the AAD screening program.
The reason PD patients have an increased skin cancer risk is still not clear. While a possible relationship between levodopa and melanoma has long been debated, Dr. Bertoni said this study found no such association.
"Eighty-five percent of patients in this study were either currently taking levodopa or had used it in the past, but we found no increased melanoma risk associated with the drug," he said.
The majority of PD patients, noted Dr. Bertoni, had at least 1 or 2 of 13 standard melanoma risk factors, including fair complexion, blue eyes, severe blistering sunburn in childhood, sun sensitivity, freckles, blonde or red hair, other skin cancer (past or present), large or irregular pigmented lesions, congenital moles, family history of melanoma, changes in moles, prior melanoma, or immunosuppression.
"We know that living on a farm or in a rural setting is a risk factor for PD, so it could be that in this setting people have more sun exposure. It could also be that US farmers tend to be blue eyed and fair skinned and tend to burn. Further, it may be that patients in these settings don't have the same access to dermatologists as people living in urban areas. However, at this point, we just don't have enough information to draw any firm conclusions," said Dr. Bertoni.
Nevertheless, patients should be advised of the increased skin cancer risk associated with PD and be referred to a dermatologist for baseline and follow-up skin examinations. In addition, Dr. Bertoni said, patients should be told how to protect themselves through vigilant use of sun block and protective clothing.
"The initial diagnosis of Parkinson's disease is an ideal time for neurologists to discuss the potential melanoma risk with their patients. It goes without saying that all individuals should be advised about skin cancer prevention, but it is especially important for those with Parkinson's disease," he said.