Motor Neuron Disease and Risk of Cancer: A Population-Based Cohort Study in Denmark

BACKGROUND: Some neurogenerative diseases have been linked to a reduced risk of cancer, but the association between motor neuron disease and cancer risk is not well understood. We hypothesized that cancer risk would be lower among those with motor neuron disease and its most common subtype, amyotrophic lateral sclerosis. METHODS: We conducted a population-based cohort study of motor neuron disease and cancer risk using routinely collected data from population-based registries in Denmark. We examined cancer incidence among patients diagnosed with motor neuron disease between January 1980 and December 2013 followed through 2013. Using Danish national cancer rates for the study period, we computed standardized incidence ratios as a measure of relative risks. RESULTS: In the cohort of 5053 patients with a motor neuron disease, the overall standardized incidence ratio of any cancer was 1.17 (95% confidence interval [CI], 1.03–1.31); the corresponding standardized incidence ratio for amyotrophic lateral sclerosis was 1.24 (95% CI, 0.96–1.57). The standardized incidence ratios of any cancer in the cohort with motor neuron disease was 1.52 (95% CI, 1.22–1.87) for <1 year of follow-up; 0.87 (95% CI, 0.68–1.09) for years 1–5 of follow-up; and 1.22 (95% CI, 1.01–1.46) for >5 years of follow-up. Beyond one year of follow-up, patients in the motor neuron disease had elevated standardized incidence ratios for lymphoid leukemia, non-Hodgkin lymphoma, and basal cell skin cancer. CONCLUSION: Findings fail to support the hypothesis that motor neuron disease or amyotrophic lateral sclerosis is associated with reduced cancer incidence. An elevated risk of cancer during the first year of follow-up may be attributable to heightened surveillance.