Closing the gap of older adult recruitment to cancer clinical trials: a scoping review

Background: Although they constitute a large proportion of those with cancer, older adults remain underrepresented in cancer clinical trials (CCTs). This scoping review aims to map the available literature regarding barriers and enablers to the recruitment of older adults to CCTs. Methods: A comprehensive literature search was conducted in CINAHL, PsycINFO, PubMed/MEDLINE, C2-SPECTR Campbell Systematic Reviews and Cochrane Library from 2004 to January 2026. Records were screened by two independent reviewers. Data related to study characteristics and findings were extracted in duplicate. Original research including older adult participants (having a median/mean age of 60 years or older) with any cancer diagnosis (haematological or solid tumour), which explored factors relating to their recruitment to CCTs were eligible for inclusion. Results: A total of 29,160 records were identified through database searches. After screening, 30 studies met the inclusion criteria. Fifteen studies investigated patients, 3 investigated patients and carers, 4 investigated physicians/oncologists or providers, 2 investigated researchers and 6 had mixed populations. Studies were conducted in the USA (n = 19), Canada (n = 4), the Netherlands (n = 2), France (n = 3), Germany (n = 1) and Ireland (n = 1). Interpersonal, intrapersonal, environmental and institutional factors were the most commonly cited factors influencing CCT participation. Notably, the caregiver perspective was underexplored, despite caregivers often being framed as integrally important for making CCT decisions. Among the factors that could be modified were the physician/patient relationship, lack of information, and mistrust. Seven studies were identified that focused on interventions to increase recruitment, with varying approaches utilised. Conclusion: Intrapersonal, interpersonal, institutional and environmental factors were among the most cited influences on CCT participation in older adults. The patient-physician relationship appeared to hold substantial influence, acting to both discourage or encourage participation, with institutional factors limiting clinicians’ ability to communicate about trials. Greater consideration of the opinions of carers is recommended, given their importance in supporting treatment. Identification of these factors can inform the development of future research and can provide actionable insights into how CCT teams may encourage participation of older adults. Institutional commitment will be needed to ensure equitable access to trials, with further studies examining recruitment strategies required to justify the resource-intensive nature of this effort.