A Systematic Review of Recruitment and Retention Strategies Used in Dietary Randomized Controlled Interventions in Cancer Survivors

Abstract

Interpretation of results of dietary intervention trials in cancer survivors may be limited by insufficient recruitment or retention of study participants. This systematic review describes recruitment strategies, accrual of participants, and attrition (withdrawal) rates for dietary interventions conducted in breast, prostate, and colorectal cancer survivors. PubMed, CINAHL, Cochrane Central Register of Controlled Trials, Embase, PsychINFO, and Web of Science databases were searched. Eligible studies included national and international dietary randomized controlled trials (RCTs), with at least 12 weeks of intervention and 6 months of follow-up. Trials were required to include a CONSORT (CONsolidated Standards of Reporting Trials) diagram. Twenty cohorts were included: breast cancer (BC) survivors (n=11), prostate cancer (PC) (n=3), colorectal cancer (CRC) (n=1), and combined (n=5). Primary recruitment methods included health care providers (n=13) or cancer registries (n=9). Of studies that set a priori sample sizes, 12 met accrual targets and five did not. Attrition rates averaged 18.6% at 6 months, 16.3% at 12-13 months, and 20.3% at 2 years. Among completed studies (n=18), seven trials met a priori retention targets, three trials did not, one assessed feasibility, and seven trials did not provide a clearly defined retention goal. There were few trials in PC and CRC survivors. Missing CONSORT diagrams reduced the eligible studies. The majority of studies met recruitment goals (n=12). Overall, attrition rates averaged approximately 17.4%. Improved understanding of effective recruitment and retention strategies requires more diligent reporting. Qualitative research may allow for more systematic and detailed evaluation of challenges that contribute to insufficient recruitment and retention of cancer survivors in dietary intervention trials. Registration can be found at PROSPERO ref: CRD42018070396.