Who will drop out and who will drop in: exercise adherence in a randomized clinical trial among patients receiving active cancer treatment.

Background: Adherence has significantly affected the efficacy of a randomized clinical trial (RCT) to test exercise interventions.

Objective: The aims of this study were to analyze exercise-related adherence patterns among patients receiving active cancer treatment and to identify factors related to exercise adherence and contamination in both the intervention and control groups.

Methods: This is a secondary analysis of data from an RCT of a home-based walking intervention for patients receiving active cancer treatment. Hierarchical Poisson regression analysis was used to identify factors related to exercise adherence and exercise contamination in the exercise intervention and control groups.

Results: A total of 126 patients finished the study. Exercise adherence rate in the intervention group was 32.35%, whereas exercise contamination rate in the control group was 12.07%. Independent predictors of adherence for the exercise group were baseline physical fitness, pretreatment fatigue level, treatment-related mood disturbance, and marital status (P < .01); exercise history significantly predicted exercise contamination (P < .00) in the control group.

Conclusion: Adherence remains an issue in an exercise RCT among patients on active cancer treatment. Adherence is related to symptom, physical function, and exercise history.

Implications For Practice: Exercise researchers should consider stratifying samples based on pretreatment variables found to be significantly associated with outcome variables in this study to reduce confounding effects. Oncology clinicians can use the study findings to appropriately tailor strategies to encourage exercise adherence among patients receiving active cancer treatment so that these patients can receive the known benefits of exercise.