New evidence of the relative protective effects of neurodegenerative diseases and cancer against each other.

BACKGROUND: Cancer and degenerative diseases share some pathogenic mechanisms which act in opposition to one another to produce either uncontrolled cell proliferation or cell death. According to several studies, patients with Alzheimer disease have a lower risk of neoplasia, and vice versa. This study describes the prevalence of tumours (active or successfully treated) in a series of patients with and without a dementing degenerative disease treated at a cognitive neurology unit.

PATIENTS AND METHOD: We analysed the frequency and topography of tumours and the presence or absence of a neurodegenerative disease in a group of 1,164 patients. Neurodegenerative diseases were classified in 4 groups: Alzheimer disease, synucleinopathies, Pick complex, and polyglutamine complex. We subsequently compared tumour frequency in patients with and without a degenerative disease, and prevalence of neurodegenerative diseases in patients with and without tumours.

RESULTS: Tumours were detected in 12.1% of the patients with a neurodegenerative disease and in 17.3% of the remaining patients. Around 14.8% of the patients with a history of neoplasia and 20.8% of the patients with no history of neoplasia were diagnosed with a neurodegenerative disease. Except for these differences and the differences between subgroups (type of degenerative disease and tumour location) were not statistically significant, except when comparing neurodegenerative diseases to central nervous system tumours, and synucleinopathies to neoplasms.

CONCLUSION: Dementing degenerative diseases and neoplastic disorders are not mutually exclusive. Nevertheless, the rate of co-occurrence is lower than would be expected given the prevalence rate for each group.