The relationship between global and specific components of quality of life, assessed with the EORTC QLQ-C30 in a sample of 2019 cancer patients

Quality of life (QoL) is impaired in many cancer patients. The aim of this study was to test whether detriments in QoL were less pronounced in global assessments of QoL compared to more specific components. A total of 2059 cancer patients with mixed diagnoses were examined 6 months after discharge from a cancer rehabilitation clinic. QoL was measured with the EORTC QLQ-C30, which contains a global QoL scale, and 14 functioning and symptom scales and symptom items. A sample of the general population (n = 4476) served as controls. Regression analyses were performed to calculate expected mean scores for the patients, based on their age and gender distribution. Global QoL in the cancer sample (M = 69.3) was nearly equal to that of the general population, while the mean scores of all functioning scales, symptom scales and symptom items showed markedly worse QoL. This general relationship between global and specific QoL was found for seven of eight cancer types. The results indicate that global QoL is not the sum of its parts. This should be considered when treatment effects on QoL are examined. One alternative is to use higher order summarising functioning and symptom scales.