Factors influencing withdrawal without a defined reason in oncology trials.

• DOI: 10.1200/jco.2025.43.16_suppl.e23014
• Publication Date: 2025-05-28T17:31:48Z
• Authors: Rodrigo Paredes; Alexander B Karol; Anna Argulian; Kasopefoluwa Ogun...; Lexi S. Weintraub; Justin Miller; Yu Fujiwara; Himanshu Joshi; Deborah Blythe Do...; Matthew D. Galsky
• Keywords: Clinical Oncology

e23014 Background: Withdrawal without a defined reason (WWDR) undermines the reliability and interpretability of clinical trial results poses critical challenge for design. The underlying factors driving WWDR remain poorly understood. This study seeks to identify trial-level associated with that can be intervened upon improve participant retention. Methods: We systematically reviewed therapeutic phase 3 oncology trials registered on ClinicalTrials.gov from August 20, 2014 2024. Supportive care those lacking flow diagram or equivalent were excluded. was as withdrawal initiated by either patients investigators specified cause recorded (e.g. nonadherence, patient requests, loss follow-up). Generalized Additive Models bidirectional stepwise selection used perform multivariate regression. Continuous variables standardized associations evaluated rate ratio (RR). Results: 300 studies met inclusion criteria, including 165,674 patients. median follow-up 35.6 months (Interquartile range [IQR]: 4.4–66.8), enrollment size 480.5 participants (IQR: 259–702). Most focused solid tumors (76.2%, n = 232), mainly metastatic (77.2%, 179), fewer addressing earlier stage disease (22.8%, 53). Hematologic malignancies accounted 23.2% (n 70). majority randomized (88.0%, 264), unblinded (61.7%, 185), industry-sponsored (90.7%, 272), conducted internationally (95.0%, 285), multi-site (93.7%, 281). Key predictors are detailed in Table 1. Industry sponsorship linked 67% higher likelihood (RR: 1.67, 95% CI: 1.18–2.57, p 0.02), larger enrollments showed increased per standard deviation (SD) (SD 491; RR: 1.13, 1–1.28, 0.045). model explained 14.3% variance. Conclusions: Industry-sponsored significantly rates WWDR. In contrast, combination therapies radiotherapy (RT) reduces these rates. Trials often face logistical complexities variability across sites, while may impose stricter protocols, raising Combination RT retention increasing interaction monitoring inherent treatments. Future research should analyze patient-level clarify strategies reduce prior enrollment. Trial-level Predictor OR (95% CI) p-value therapy 0.73 (0.56, 0.93) 0.01 Solid tumor receiving definitive 0.21 (0.10, 0.37) <0.001 Trial (per SD increase)* 1.13 (1, 1.28) 0.045 1.67 (1.18, 2.57) 0.02 Standardized 491