Abstract Introduction Older adults with cancer often require multiple medications (polypharmacy) comprising cancer-specific treatments, supportive care medications (e.g. analgesics) and medications for pre-existing conditions. The reported prevalence of polypharmacy in older adults with cancer ranges from 13–92% (1). Increasing numbers of medications pose risks of potentially inappropriate prescribing and medication non-adherence. Aim The aim of this scoping review was to provide an overview of evaluations of interventions to optimise medication prescribing and/or adherence in older adults with cancer, with a particular focus on the interventions, study populations and outcome measures that have been assessed in previous evaluations. Methods Four databases (PubMed, EMBASE, CINAHL, PsycINFO) were searched from inception to 29th November 2019 using relevant search terms (e.g. cancer, older adults, prescribing, adherence). Eligible studies evaluated interventions seeking to improve medication prescribing and/or adherence in older adults (≥65 years) with an active cancer diagnosis using a comparative evaluation (e.g. inclusion of a control group). All outcomes for studies that met inclusion criteria were included in the review. Two reviewers independently screened relevant abstracts for inclusion and performed data extraction. As a scoping review aims to provide a broad overview of existing literature, formal assessments of methodological quality of included studies were not undertaken. Extracted data were collated using tables and accompanying narrative descriptive summaries. The review was reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for scoping reviews (PRISMA-ScR) guidelines (2). Results The electronic searches yielded 21,136 citations (Figure 1). Nine studies met inclusion criteria. Included studies consisted of five randomised controlled trials (RCTs), including one cluster RCT, and four before-and-after study designs. Studies were primarily conducted in oncology clinics, ranging from single study sites to 109 oncology clinics. Sample sizes ranged from 33 to 4844 patients. All studies had a sample population with a mean/median age of ≥65 years, however, only two studies focused specifically on older populations. Interventions most commonly involved patient education (n=6), and were delivered by pharmacists or nurses. Five studies referred to the intervention development process and no studies reported any theoretical underpinning. Three studies reported on prescribing-related outcomes and seven studies reported on adherence-related outcomes, using different terminology and a range of assessments. Prescribing-related outcomes comprised assessments of medication appropriateness (using Beers criteria), drug-related problems and drug interactions. Adherence-related outcomes included assessments of self-reported medication adherence and calculation of patients’ medication possession ratio. Conclusion The main strength of this scoping review is that it provides a broad overview of the existing literature on interventions aimed at optimising medication prescribing and adherence in older adults with cancer. The review highlights a lack of robust studies specifically targeting this patient population and limited scope to pool outcome data across included studies. Limitations of the review were that searches were restricted to English language publications and no grey literature was searched. Future research should focus specifically on older patients with cancer, and exercise rigour during intervention development, evaluation and reporting in order to generate findings that could inform future practice. References 1. Maggiore RJ, Gross CP, Hurria A. Polypharmacy in older adults with cancer. The oncologist. 2010;15(5):507–22. 2. Tricco AC, Lillie E, Zarin W, O'Brien KK, Colquhoun H, Levac D, et al. PRISMA Extension for Scoping Reviews (PRISMA-ScR): Checklist and Explanation. Ann Intern Med. 2018;169(7):467–73.