Attrition in NRG Oncology's Radiation-Based Clinical Trials

• Type of Material: Article
• Authors: Connie M. Ulrich, University of Pennsylvania; Snehal Deshmukh, NRG Oncology Statistics and Data Management Center; Stephanie L. Pugh, NRG Oncology Statistics and Data Management Center; Alexandra Hanlon, University of Pennsylvania; Christine Grady, National Institutes of Health; Deborah W. Bruner, Emory University; Walter Curran Jr, Emory University
• Language: English
• Date: 2018-09-01
• Publisher: ELSEVIER SCIENCE INC
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2018 Elsevier Inc. All rights reserved. CC BY NC ND 4.0
• Final Published Version (URL): http://dx.doi.org/10.1016/j.ijrobp.2018.04.078
• Title of Journal or Parent Work: International Journal of Radiation Oncology - Biology - Physics
• Volume: 102
• Issue: 1
• Start Page: 26
• End Page: 33
• Grant/Funding Information: This project was supported by grants U10CA21661, U10CA180868, U10CA180822 from the National Cancer Institute (NCI); and this project is funded in part by the Pennsylvania Department of Health Formula Grant 4100037703.
• Keywords: REGRESSION-MODELS; Oncology; Life Sciences & Biomedicine; CANCER; BARRIERS; WOMEN; REPRESENTATION; PREVENTION; Radiology, Nuclear Medicine & Medical Imaging; Science & Technology
• Research Categories: Health Sciences, Oncology

Abstract

Purpose: To determine individual, organizational, and protocol-specific factors associated with attrition in NRG Oncology's radiation-based clinical trials. Methods and Materials: This retrospective analysis included 27,443 patients representing 134 NRG Oncology's radiation-based clinical trials.trials with primary efficacy results published from 1985-2011. Trials were separated on the basis of the primary endpoint (fixed time vs event driven). The cumulative incidence approach was used to estimate time to attrition, and cause-specific Cox proportional hazards models were used to assess factors associated with attrition. Results: Most patients (69%) were enrolled in an event-driven trial (n = 18,809), while 31% were enrolled in a fixed-time trial (n = 8634). Median follow-up time for patients enrolled in fixed-time trials was 4.1 months and 37.2 months for patients enrolled in event-driven trials. Fixed time trials with a duration < 6 months had a 5 month attrition rate of 4.3% (95% confidence interval [CI]: 3.4%, 5.5%) and those with a duration ≥ 6 months had a 1 year attrition rate of 1.6% (95% CI: 1.2, 2.1). Event-driven trials had 1- and 5-year attrition rates of 0.5% (95% CI: 0.4%, 0.6%) and 13.6% (95% CI: 13.1%, 14.1%), respectively. Younger age, female gender, and Zubrod performance status >0 were associated with greater attrition as were enrollment by institutions in the West and South regions and participation in fixed-time trials. Conclusions: Attrition in clinical trials can have a negative effect on trial outcomes. Data on factors associated with attrition can help guide the development of strategies to enhance retention. These strategies should focus on patient characteristics associated with attrition in both fixed-time and event-driven trials as well as in differing geographic regions of the country.