Moderators of the effects of group-based physical exercise on cancer survivors' quality of life.

ABSTRACT

PURPOSE: This study explored demographic, clinical, and psychological moderators of the effect of a group-based physical exercise intervention on global quality of life (QoL) among cancer survivors who completed treatment. METHODS: Cancer survivors were assigned to a 12-week physical exercise (n = 147) or a wait-list control group (n = 62). The main outcome measure was global QoL, assessed with the EORTC QLQ-C30 at baseline and 12 weeks later. Potential moderators were age, gender, education level, marital status, employment status, type of treatment, time since treatment, the presence of comorbidities, fatigue, general self-efficacy, depression, and anxiety. Linear regression analyses were used to test effect modification of the intervention by each moderator variable using interaction tests (p ≤ 0.10). RESULTS: The physical exercise intervention effect on global QoL was larger for cancer survivors who received radiotherapy (ß = 10.3, 95 % confidence interval (CI) = 4.4; 16.2) than for cancer survivors who did not receive radiotherapy (ß = 1.8, 95 % CI = -5.9; 9.5, p interaction = 0.10), larger for cancer survivors who received a combination of chemoradiotherapy (ß = 13.0, 95 % CI = 6.0; 20.1) than for those who did not receive this combination of treatments (ß = 2.5, 95 % CI = -3.7; 8.7, p interaction = 0.02), and larger for cancer survivors with higher baseline levels of fatigue (ß = 12.6, 95 % CI = 5.7; 19.6) than for those with lower levels (ß = 2.4, 95 % CI = -3.9; 8.7, p interaction = 0.03). No other moderating effects were found. CONCLUSIONS: This study suggests that cancer treatment modality and baseline fatigue levels moderate the effect of a physical exercise program on cancer survivors'global QoL.