Reporting of Adherence-Related Information in Randomized Controlled Trials of Oral Chinese Herbal Medicine for Cancer: A Cross-Sectional Study.

Background: Adherence is important for the internal validity of randomized controlled trials (RCTs), but adherence-related reporting in oral Chinese herbal medicine (CHM) RCTs for cancer has not been systematically examined. This study assessed reporting practices before the release of the CONSORT 2025 statement and explored factors associated with intervention completion. Methods: PubMed, Web of Science, EMBASE, and the Cochrane Library were searched for eligible studies published between January 2010 and April 2025. Study characteristics, adherence-related reporting, monitoring methods, and intervention completion were extracted. Binary logistic regression identified factors associated with reporting of adherence-related information. In parallel-group RCTs using CHM only in the intervention group, beta-binomial regression was used as the primary model to assess factors associated with intervention completion. Results: A total of 113 studies were included, and 51 (45.1%) reported adherence-related information. English-language publication, higher modified Jadad score, and reporting of adherence monitoring methods were associated with reporting of adherence-related information. Only 24 studies (21.2%) described adherence monitoring methods, with diary cards being the most common. Mean intervention completion across the 51 studies was 93.4%. In 43 parallel-group RCTs, placebo use (OR = 0.38, 95% CI: 0.24-0.60; P < 0.001) and syndrome differentiation-guided treatment adjustment (OR = 0.58, 95% CI: 0.37-0.91; P = 0.019) were associated with lower intervention completion in the CHM intervention group, whereas solid dosage forms were associated with higher intervention completion (OR = 2.11, 95% CI: 1.26-3.55; P = 0.005). The directions of the associations were generally consistent across sensitivity analyses. Conclusion: Before the release of CONSORT 2025, adherence-related reporting in oral CHM RCTs for cancer was inadequate and non-standardized. Placebo use, syndrome differentiation-guided treatment adjustment, and oral dosage form were associated with intervention completion. These findings may inform adherence reporting and the design of future CHM trials.