A review of patient recruitment in randomised controlled trials of preoperative exercise

Background: Randomised controlled trials (RCTs) are considered the gold standard design to determine the effectiveness of an intervention, as the only method of decreasing section bias and minimising random error. However, participant recruitment to randomised controlled trials is a major challenge, with many trials failing to recruit the targeted sample size accordingly to the planned protocol. Thus, the aim of this review is to detail the recruitment challenges of preoperative exercise clinical trials. Methods: A comprehensive search was performed on MEDLINE, Embase, The Cochrane Library, CINAHL, AMED and PsycINFO from inception to July 2021. Randomised controlled trials investigating the effectiveness of preoperative exercise on postoperative complication and/or length of hospital stay in adult cancer patients were included. Main outcomes included recruitment rate, retention rate, number of days needed to screen and recruit one patient and trial recruitment duration. Descriptive statistics were used to summarise outcomes of interest. Results: A total of 27 trials were identified, including 3656 patients screened (N = 21) and 1414 randomised (median recruitment rate (interquartile range) = 53.6% (25.2%-67.6%), N = 21). The sample size of the included trials ranged from 19 to 270 (median = 48.0; interquartile range = 40.0-85.0) and the duration of trial recruitment ranged from 3 to 50 months (median = 19.0 months; interquartile range = 10.5-34.0). Overall, a median of 3.6 days was needed to screen one patient, whereas 13.7 days were needed to randomise one participant. Over the trials duration, the median dropout rate was 7.9%. Variations in recruitment outcomes were observed across trials of different cancer types but were not statistically significant. Conclusion: The recruitment of participants to preoperative exercise randomised controlled trials is challenging, but patient retention appears to be less of a problem. Future trials investigating the effectiveness of a preoperative exercise programme following cancer surgery should consider the time taken to recruit patients. Strategies associated with improved recruitment should be investigated in future studies.