doi:10.1186/s12885-017-3594-9engGarcía Rodríguez, L.A.Soriano-Gabarró, M.Bromley, S.Lanas, A.Cea Soriano, L.New use of low-dose aspirin and risk of colorectal cancer by stage at diagnosis: A nested case-control study in UK general practiceART-2017-101625Background: Evidence from clinical trial populations suggests low-dose aspirin reduces the risk of colorectal cancer (CRC). Part of this reduction in risk might be due to protection against metastatic disease. Methods: We investigated the risk of CRC among new-users of low-dose aspirin (75-300mg), including risk by stage at diagnosis. Using The Health Improvement Network, we conducted a cohort study with nested case-control analysis. Two cohorts (N=170, 336 each) aged 40-89years from 2000 to 2009 and free of cancer were identified: i) new-users of low-dose aspirin, ii) non-users of low-dose aspirin, at start of follow-up, matched by age, sex and previous primary care practitioner visits. Patients were followed for up to 12years to identify incident CRC. 10, 000 frequency-matched controls were selected by incidence density sampling where the odds ratio is an unbiased estimator of the incidence rate ratio (RR). RRs with 95% confidence intervals were calculated. Low-dose aspirin use was classified ''as-treated'' independent from baseline exposure status to account for changes in exposure during follow-up. Results: Current users of low-dose aspirin (use on the index date or in the previous 90days) had a significantly reduced risk of CRC, RR 0.66 (95% CI 0.60-0.74). The reduction in risk was apparent across all age groups, and was unrelated to dose, indication, gender, CRC location or case-fatality status. Reduced risks occurred throughout treatment duration and with all low-dose aspirin doses. RRs by aspirin indication were 0.71 (0.63-0.79) and 0.60 (0.53-0.68) for primary and secondary cardiovascular protection, respectively. Among cases with staging information (n=1421), RRs for current use of low-dose aspirin were 0.94 (0.66-1.33) for Dukes Stage A CRC, 0.54 (0.42-0.68) for Dukes B, 0.71 (0.56-0.91) for Dukes C, and 0.60 (0.48-0.74) for Dukes D. After 5years'' therapy, the RR for Dukes Stage A CRC was 0.53 (0.24-1.19). Conclusions: Patients starting low-dose aspirin therapy have a reduced risk of Stages B-D CRC, suggesting a role for low-dose aspirin in the progression of established CRC; a substantial reduction in the risk of Dukes A CRC may occur after 5years'' therapy.2017http://zaguan.unizar.es/record/6300910.1186/s12885-017-3594-9http://zaguan.unizar.es/record/63009oai:zaguan.unizar.es:63009BMC CANCER 17, 1 (2017), [11 pp]byhttp://creativecommons.org/licenses/by/3.0/es/info:eu-repo/semantics/openAccess