RCT of a psychological intervention for patients with cancer: I. mechanisms of change

Abstract

Little is known about the therapeutic processes contributing to efficacy of psychological interventions for patients with cancer. Data from a randomized clinical trial yielding robust biobehavioral and health effects (B. L. Andersen et al., 2004, 2007) were used to examine associations between process variables, treatment utilization, and outcomes. Novel findings emerged. Patients were highly satisfied with the treatment, but their higher levels of felt support (group cohesion) covaried with lower distress and fewer symptoms. Also, specific treatment strategies were associated with specific outcomes, including lower distress, improved dietary habits, reduced symptomatology, and higher chemotherapy dose intensity. These data provide a comprehensive test of multiple therapeutic processes and mechanisms for biobehavioral change with an intervention including both intensive and maintenance phases.

Figure 1

CONSORT flowchart. *Cumulative values across therapy phases.

Figure 2

Estimated trajectories of change in the patients' Profile of Mood States Total Mood Disturbance (POMS TMD) scores by level of cohesion. Whereas patients feeling less support from the group showed no change in the level of their emotional distress, those reporting high levels of cohesion from the intensive phase experienced mood improvement through the shift to maintenance sessions.

Figure 3

Estimated trajectories of change in the patients' Food Habits. Questionnaire scores by level of dietary strategies use. The findings suggest that more frequent dietary strategies use was associated with greater positive change in food habits, an effect most pronounced during the intensive phase but still evident during maintenance.

Figure 4

Estimated trajectories of change in the patients' reported frequency of their relaxation practice and the nurses' ratings of the patients' symptoms and signs. The findings suggest more frequent relaxation use by those with the highest levels of symptoms, who then achieved the greatest decline in symptoms.

Figure 5

Estimated trajectories over time in the patients' reports of physical activity and the nurses' ratings of the patients' symptoms and signs. The findings suggest that the patients who made the most use of exercise strategies were those with the highest levels of symptoms, who then achieved a rapid, steep decline in symptoms exceeding that of all others who exercised less.