Psychometric Evaluation of the Cancer Dependent Quality of Life (CancerDQoL) Questionnaire: An Individualised Measure of the Impact of Cancer and Its Treatment on Quality of Life.

Abstract

The Cancer Dependent Quality of Life (CancerDQoL) questionnaire asks about the impact of cancer and its treatment on individuals' quality of life (QoL). This study evaluates the psychometric properties of the CancerDQoL in a UK sample. Patients (n=159) with a range of cancers, recruited from Barts Health NHS Trust and Barts Maggie's Centre, completed self-administered questionnaires: CancerDQoL, EQ-5D-VAS (health status), EORTC-QLQ-C30 (predominantly health symptoms/functioning) and W-BQ16 (well-being). Based on the pre-existing -DQoL template and Item Library (Bradley), the CancerDQoL includes 23 cancer-specific life-domain items and four overview items. Exploratory factor analysis revealed a 22-item, single-factor solution. Internal consistency was excellent (α=0.94). Cancer negatively impacted all life domains: 'feelings about future' had the most negative mean weighted (by importance) impact (WI) score. 'Physical abilities' WI scores were ranked 12th. CancerDQoL Average Weighted Impact (AWI) scores were more strongly correlated with the Cancer-dependent QoL overview item than with the General QoL or General Health overview items. As expected, the EQ-5D-VAS and EORTC-QLQ-C30 correlated together more strongly than with CancerDQoL AWI scores. The CancerDQoL is the first individualised questionnaire measuring the impact of cancer and its treatment on QoL. The CancerDQoL AWI score is related to, but different from, measures of health status/functioning and well-being. Eleven CancerDQoL life-domains were more negatively impacted/important than physical abilities which is a major focus of the EQ-5D and EORTC-QLQ-C30. By revealing aspects of life most impacted by cancer and its treatment, efforts can be prioritised to improve QoL for people with cancer.