Posttraumatic growth and health-related quality of life in cancer survivors: Does fatigue moderate the link?

Interest in post-traumatic growth (PTG) as a predictor of health-related quality of life (HRQoL) is currently gaining attention. However, current evidence is still inconclusive on the nature of this relationship. The first objective of this study was to investigate the relationship between PTG and global HRQoL among cancer survivors. We further investigated the moderating role of fatigue in the association between PTG and global HRQoL. In the FiX study (Fatigue in Germany - Examination of prevalence, severity, and state of screening and treatment) cancer-related fatigue (EORTC QLQ-FA12), PTG inventory and global HRQoL (EORTC QLQ-C30) were assessed four years after cancer diagnosis in 1316 cancer-free survivors (mean age = 67.28, SD = 11.05, 51.4% female). Multiple linear regression analysis and moderation analysis were performed. The results showed that PTG had a convex quadratic relationship with global HRQoL (p < 0.001). Contrary to our hypothesis, fatigue did not moderate the relationship between PTG (linear and quadratic terms) and global HRQoL, neither when considering the overall PTG score nor for any PTG subdimension. In conclusion, PTG has a convex quadratic relationship with long-term global HRQoL that was not modified by persisting fatigue. Future statistical models investigating PTG and global HRQoL should take this non-linear relationship into account. Aiming to increase PTG might contribute to, but is likely not sufficient for high levels of global HRQoL in cancer survivors in the long run.