A study that used a Utah genealogic database and the Utah Cancer Registry to examine the relationship between Parkinson disease and cancer suggests an increased risk of prostate cancer and melanoma in patients with Parkinson disease and their relatives.

According to a report published Online First on September 3, 2012 by Archives of Neurology, a JAMA Network publication, some neurodegenerative diseases, in particular Parkinson disease, may share common pathogenic mechanisms with some cancers. Identifying a genetic relationship between Parkinson disease and cancer could allow oncologists to provide proper assessment of cancer risk in patients with Parkinson disease and might also have implications for the counselling of relatives of patients.

Cancer risk in patients with Parkinson disease
Seth A. Kareus, M.D. and colleagues from the University of Utah, Salt Lake City, estimated relative risks for cancer in individuals with Parkinson disease listed on their death certificate, and in their relatives. The study identified 2,998 patients with Parkinson disease listed as their cause of death from 1904 to 2008 and also included information from the Utah Cancer Registry on 100,817 patients diagnosed with cancer.

To validate their observed associations, researchers also estimated the reciprocal relative risk for Parkinson disease death among patients diagnosed with melanoma and their relatives. They also estimated the relative risks for death with Parkinson disease among patients diagnosed with prostate cancer and their relatives. Kareus and his team observed a reciprocal significantly increased risk for Parkinson disease in the 22,147 prostate cancer cases and their relatives. A reciprocal significantly increased relative risk for Parkinson disease was found in 7,841 Utah melanoma cases and their relatives.

Estimated risk of Melanoma
Among the individuals with Parkinson disease who died, the authors observed 48 cases of melanoma. The estimated relative risk for melanoma in patients with Parkinson disease who died was 1.95; and an increased risk for death with Parkinson disease was noted among the patients with melanoma (relative risk, 1.65). The researchers also found prostate cancer in 212 patients with Parkinson disease who died (relative risk, 1.71) and an increased risk for death with Parkinson disease was found among the prostate cancer patients (relative risk, 1.39), according to the study results.

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The authors concluded that these data argue strongly for a significant shared genetic risk for specific cancers on the one hand and neurodegeneration on the other. The findings provide a framework for future definition of the precise nature of shared genetic variation leading to neurodegeneration in some individuals, and melanoma or prostate cancers in others, and they may influence strategies for melanoma and prostate cancer screening.

Families with Parkinson disease and cancer
In an accompanied editorial, Walter A. Rocca, M.D. of the Mayo Clinic in Rochester wrote that the study findings combined with previous findings in the literature, suggest that some families have a genetic predisposition that can manifest as Parkinson disease, as other types of parkinsonism, as essential tremor, as cognitive impairment or dementia, as amyotrophic lateral sclerosis, as anxiety disorders, as depressive disorders, or as non-neurological conditions such as melanoma and prostate cancer.

If the mechanisms are primarily genetic, then it may be possible to identify genetic variants that predispose to accelerated neurodegeneration and to increased oncogenesis in the same individual or among members of some particular families. On the other hand, if Parkinson disease is multifactorial at the individual level, dimorphic in men and women, and heterogeneous at the population level, the search for one or several genetic variants may not be productive, Rocca concluded.

For more information:
– Kareus SA, Figueroa KP, Cannon-Albright LA, Pulst SM. Shared Predispositions of Parkinsonism and Cancer: A Population-Based Pedigree-Linked Study. Arch Neurol. 2012 Sep 3:1-6. doi: 10.1001/archneurol.2012.2261. [Epub ahead of print]
– Rocca WA. Families With Parkinson Disease and Cancer (Editorial|online first) Arch Neurol. 2012 Sep 3:1-2. doi: 10.1001/archneurol.2012.2664. [Epub ahead of print]

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