Aspirin use for cancer prevention: a systematic review of public, patient and healthcare provider attitudes and adherence behaviours

Background: Clinical guidelines worldwide are increasingly recommending aspirin for cancer prevention. We undertook a systematic review to synthesise the quantitative and qualitative data on attitudes and behaviour towards the use of aspirin for cancer prevention, and healthcare providers’ attitudes and behaviour towards implementing aspirin in clinical care. Design: In February 2020, we searched: MEDLINE, EMBASE, CINAHL, Web of Science, Cochrane Library, DARE, NHS EED, HTA Database, clinical trial registries and ProQuest Dissertations & Theses. Peer-reviewed studies on the use of aspirin for cancer prevention were included. We used the Mixed Methods Appraisal Tool to evaluate study quality, and conducted a narrative synthesis of the data. The review was pre-registered (PROSPERO: CRD42018093453). Results: Forty-two studies were identified. Uptake and adherence data were all from trials. Trials recruited healthy participants, those at higher risk of cancer (e.g. colorectal), and those with cancer (e.g. breast, colorectal). Four trials reported uptake data, of which three found low to medium uptake rates (3.7-40.9%). Most trials (18/22) reported high day-to-day adherence (≥80%). Among trials reporting data at three years, 38.6-93.6% were still using aspirin at follow-up. Four studies investigated the factors associated with adherence, and none with uptake. Three trials observed no association between gender and adherence levels. One trial found no association between colorectal cancer risk and adherence levels. Three studies observed low rates (3.2-34.5%) of healthcare providers recommending aspirin in clinical practice. No qualitative studies were identified. Conclusion: Most patients and members of the public who are offered aspirin for cancer prevention do not initiate preventive therapy. Day-to-day adherence was high among those using aspirin, but persistence may be a problem where long-term use is required. Further research is needed to identify the factors affecting aspirin use, and the barriers to implementing aspirin into clinical care.