Cancer history and risk factors in healthy older people enrolling in the ASPREE clinical trial

Background: Cancer is a leading cause of death globally. Given the elevated risk of cancer with age and an ageing population, it is important to understand the changing burden of cancer in older populations. The ASPirin in Reducing Events in the Elderly (ASPREE) study randomised healthy older individuals to 100 mg aspirin or placebo, with clinical outcomes and disability-free survival endpoints. Detailed baseline data provides a rare opportunity to explore cancer burden in a uniquely healthy older population.

Methods: At study enrolment (2010-2014), self-reported personal cancer history, cancer type and cancer risk factor data were sought from 19,114 participants (Australia, n = 16,703; U.S., n = 2411). Eligible participants were healthy, free of major diseases and expected to survive 5 years.

Results: Nearly 20% of enrolling ASPREE participants reported a prior cancer diagnosis; 18% of women and 22% of men, with women diagnosed younger (16% vs 6% of diagnoses <50 years). Cancer prevalence increased with age. Prevalence of prostate and breast cancer history were higher in U.S. participants; melanoma and colorectal cancer were higher in Australian participants. Cancer history prevalence was not associated with contemporary common risk factors nor previous aspirin use, but was associated with poor health ratings in men. Blood and breast cancer history were more common with past aspirin use.

Conclusions: Personal cancer history in healthy older ASPREE participants was as expected for the most common cancer types in the respective populations, but was not necessarily aligned with known risk factors. We attribute this to survivor bias, likely driven by entry criteria.