Inclusion criteria, exclusion criteria and study summary
Background: Cancer is a global problem. There is significant pre-clinical and epidemiological evidence demonstrating that aspirin has anti-cancer effects. Recently, individual patient data meta-analyses, from trials designed to assess cardiovascular benefits of aspirin, have shown reductions in cancer incidence and mortality associated with regular aspirin use. Additionally, the CAPP2 trial has demonstrated that daily aspirin prevents cancers associated with the Lynch syndrome. In the meta-analyses, short-term effects on cancer mortality and a decrease in risk of metastases suggest a role for aspirin in the treatment as well as prevention of cancer. This is supported by several large observational datasets. Concerns over toxicity, particularly serious haemorrhage, have limited the use of aspirin in the primary prevention of cancer. In the adjuvant setting the benefit:risk ratio will be different, with higher morbidity and mortality from recurrent cancer potentially outweighing risks associated with regular aspirin use. Aim: To assess whether regular aspirin use after standard therapy prevents recurrence and prolongs survival in patients with early stage common solid tumours. International recruitment will allow assessment of the intervention in different communities. Methods: The question will be addressed in four tumour sites (colorectal, breast, gastrooesophageal, prostate) using parallel trials with a common infrastructure. Each trial will be a multicentre, phase III, double-blind, placebo-controlled randomised trial. Participants will be randomised to 100mg aspirin, 300mg aspirin or a matching placebo, to be taken daily for 5 years. Primary outcomes will depend on tumour site and trials will be separately powered, requiring 2000-3000 patients with each tumour type to demonstrate effects of aspirin on disease recurrence and survival. Secondary outcomes include overall survival, adherence, gastrointestinal complications and cardiovascular events.