Untangling the relationship between negative illness perceptions and worse quality of life in patients with advanced cancer—a study from the population-based PROFILES registry

PURPOSE: Quality of life (QoL) is an important yet complex outcome of care in patients with advanced cancer. QoL is associated with physical and psychosocial symptoms and with patients’ illness perceptions (IPs). IPs are modifiable cognitive constructs developed to make sense of one’s illness. It is unclear how IPs influence patients’ QoL. A better understanding of this relationship can inform and direct high quality care aimed at improving patients’ QoL. We therefore investigated the mediating role of anxiety and depression in the association of IPs with QoL. METHODS: Data from 377 patients with advanced cancer were used from the PROFILES registry. Patients completed measures on IPs (BIPQ), QoL (EORTC QLQ-C30), and symptoms of anxiety and depression (HADS). Mediation analyses were conducted to decompose the total effect of IPs on QoL into a direct effect and indirect effect. RESULTS: All IPs but one (“Comprehensibility”) were negatively associated with QoL (p<0.001); patients with more negative IPs tended to have worse QoL. The effect was strongest for patients who felt that their illness affected their life more severely (“Consequences”), patients who were more concerned about their illness (“Concern”), and patients who thought that their illness strongly affected them emotionally (“Emotions”). Anxiety mediated 41–87% and depression mediated 39–69% of the total effect of patients’ IPs on QoL. CONCLUSION: Negative IPs are associated with worse QoL. Anxiety and depression mediate this association. Targeting symptoms of anxiety and depression, through the modification of IPs, has the potential to improve QoL of patients with advanced cancer.