Control/Tracking Number: 09-AB-34164-ASCOAM Activity: Abstract Submission Current Date/Time: 2/16/2009 6:51:10 AM Health-Related Quality of Life indicators and overall Quality of Life: results from a cluster analysis on baseline EORTC QLQ-C30 data

Background: Increasingly randomized controlled trials in cancer research include Health-Related Quality of Life (HRQoL) alongside traditional biomedical outcome measures. The majority of these trials focus on a general cancer HRQoL measure. The objective of this meta-analysis was to identify which HRQoL indicators influence a patient’s overall quality of life, in order to better understand the changes in such a generic scale. Methods: Retrospective pooling of 29 European Organisation for Research and Treatment of Cancer (EORTC) clinical trials, among 10 cancer sites, yielded baseline EORTC QLQ-C30 data for a total of 6739 patients. A cluster analysis, using Ward’s method, was performed to determine how the 15 HRQoL indicators, and the Global Health scale (GH) in particular, cluster overall and by cancer characteristics. Cronbach’s alpha coefficient (α) was used to measure internal consistency. Dendrograms of the HRQoL indicators were plotted for each cancer type. Results: Three main clusters emerged: a physical function related cluster (physical functioning, role functioning, fatigue and pain, α = 0.83), a psychological function related cluster (emotional functioning, cognitive functioning and insomnia, α = 0.64) and a gastrointestinal cluster (nausea and vomiting and appetite loss, α = 0.68). The GH scale was found to be part of the physical function cluster in the overall dataset (α = 0.85). This result was reproduced for both metastatic and nonmetastatic patients. When looking across the 10 different cancer sites, the GH scale was mainly linked with a physical component in brain, head and neck, lung, melanoma, ovarian, pancreatic and prostate cancer. However, in breast and testicular cancer, GH was more strongly associated with the emotional scales. Conclusions:This study shows that the GH scale of the EORTC QLQ-C30 is most strongly linked with a patient’s physical status. This result is consistent across stage of disease and most cancer sites. The different results seen in patients with breast and testicular cancer deserve additional investigation.