Abstract
PURPOSE: Retention is a key marker of trial success. Poor retention can induce bias, reduce statistical power and minimise the validity of trials. This review examined retention rates in exercise trials in cancer survivors, reasons for non-retention and retention strategies utilised. METHODS: A systematic review was conducted using a predefined search strategy in EMBASE RCTs, MEDLINE OVID, CINAHL, Web of Science-Core Collection and Cochrane Central Register of Controlled Trials (CENTRAL). The search was conducted on 27/03/2023. Title and abstract screening, full text review and data extraction were completed in duplicate. RESULTS: Of 17,524 studies identified, 67 trials involving 6093 participants were included. The median overall retention rate immediately post-intervention was 89.85%, range (52.94-100%) and mean 87.36% (standard deviation 9.89%). Trials involving colorectal cancer survivors only had the highest median retention rate (94.61%), followed by breast (92.74%), prostate (86.00%) and haematological cancers (85.49%). Studies involving mixed cancer cohorts had the lowest retention rate (80.18%). The most common retention strategies were wait-list control groups, regular check-ins/reminders and free exercise equipment. Common reasons for non-retention were lost to follow-up, health problems, personal reasons including family/work commitments and travel burden, and disease progression. CONCLUSIONS: Retention rates in exercise oncology trials are approximately 90% immediately post-interventions. Our previous work highlighted variable suboptimal recruitment rates of median 38% (range 0.52-100%). Recruitment rather than retention should be prioritised for methodology research in exercise oncology. IMPLICATIONS FOR CANCER SURVIVORS: Optimising the quality of exercise oncology trials is critical to informing high quality survivorship care. PROSPERO registration number: CRD42023421359.