Performance status and depressive symptoms as predictors of quality of life in cancer patients. A structural equation modeling analysis

OBJECTIVE: This study aimed to examine whether depressive symptoms and performance status are independent predictors of both the physical and psychological domains of health-related quality of life (HRQoL) in cancer patients.

METHODS: A sample of 4020 cancer patients (mean age 58 years, 51% women) was evaluated. Depressive symptoms were measured with the patient health questionnaire and HRQoL with the European Organisation for Research and Treatment of Cancer quality of life questionnaire core 30. The impact of the illness on everyday activities was assessed with physician ratings of both the Karnofsky performance status and the Eastern Cooperative Oncology Group performance status. The simultaneous effects of depression and performance status on quality of life outcomes were estimated using structural equation modeling.

RESULTS: Both depressive symptoms and performance status independently predicted the physical and psychological domains of HRQoL. However, the impact of depressive symptoms on the physical HRQoL was stronger than the impact of performance status on the psychological HRQoL.

CONCLUSION: Our results suggest that comorbid depressive symptoms are independently associated with both physical and psychological HRQoL in cancer patients after controlling for the physician-rated performance status. Thus, comorbid depression should be taken into account when evaluating reduced HRQoL in cancer patients. To support a causal impact of depression on HRQoL, intervention studies are needed to show that improving depression enhances cancer patients' HRQoL. Copyright © 2015 John Wiley & Sons, Ltd.