(ChemotherapyAdvisor) – Patients with polyglutamine (polyQ) diseases, characterized by the expansion of CAG triplet repeats in specific genes, have a consistently decreased incidence of cancer, suggesting a common genetic protective mechanism, a study concluded in the Lancet Oncology online April 12.

The population-based study linked data on patients with Huntington disease (HD), spinobulbar muscular atrophy (SBMA), and hereditary ataxia (HA) in Sweden to the Swedish Cancer Registry. The investigators calculated standardized incidence ratios for cancers at specific sites or of specific types and compared the risks with those in the general population; also analyzed were risks in the unaffected parents of patients.

They identified 1,510 patients with HD, 471 with SBMA, and 3,425 with hereditary ataxia (analyzed as a surrogate of spinocerebellar ataxia) from January 1969 to December 2008. Cancer was diagnosed in 91 HD patients (6%), 34 SBMA patients (7%), and 421 HA patients (12%). Compared with the general population, the chances of being diagnosed with cancer were 53% lower in HD patients, 35% lower in SBMA patients, and 23% lower in HA patients. Before diagnosis of a polyQ disease, risk of cancer was even lower. Cancer risk in the unaffected parents of patients with polyQ diseases was similar to that in the general population.

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Future studies should investigate the specific biological mechanisms underlying the reduced cancer risk in patients with polyQ diseases,” the authors concluded.