These results support the EORTC QLQ-C30 as a reliable and valid measure of the quality of life of cancer patients in multicultural clinical research settings. Work is ongoing to examine the performance of the questionnaire among more heterogenous patient samples and in phase II and phase III clinical trials.

Health-related quality of life (HRQL) studies sometimes rely, in part, on proxy information obtained from patients' significant others (spouse or close companion) or health care providers. This review: (1) provides a quantitative analysis of the results that have been reported in recent studies assessing the level of agreement between patient and proxy HRQL ratings, and (2) addresses a number of key methodological issues surrounding the use of proxy raters in HRQL research. This review concentrates on 23 studies, published between 1991-2000, that describe patient-proxy agreement for a number of well-known multidimensional HRQL instruments. In general, moderate to high levels of patient-proxy agreement were reported. Lower levels of agreement were found predominantly in studies employing a small sample size (approximately 50 patient-proxy pairs or less). In larger studies comparing patients and their significant others, median correlations were between 0.60-0.70 for physical HRQL domains and about 0.50 for psychosocial domains. Mixed results were reported in studies comparing patients and their health care providers, but most of these studies employed a relatively small sample size. Proxy raters tended to report more HRQL problems than patients themselves, but the magnitude of observed differences was modest (median standardized differences of about 0.20). Based on the current evidence, we conclude that judgements made by significant others and health care providers about several aspects of patients' HRQL are reasonably accurate. Substantial discrepancies between patient and proxy ratings occur in a minority of cases. We recommend that future studies focus on: (a) the reliability and validity of proxy ratings according to common psychometric methods, and (b) the balance between information bias due to proxy ratings and potential selection bias due to exclusion of important patient subgroups from HRQL studies.

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A self-report questionnaire module consisting of 24 items, comprising 5 scales and 7 single items, has been developed for measuring health-related quality of life in patients with brain cancer. Module development proceeded through several stages, including a listing of patient, family and health care professional concerns, the writing of items, field testing in 105 patients with brain cancer and subsequent item reduction and scale construction after multitrait scaling analysis and assessment of internal consistency (Cronbach's coefficient alpha). The final version of the module exhibits reasonable test-retest stability over a period of one week. Differences in the responses between patients with recently-diagnosed and recurrent cancer and between patients with a Karnofsky Performance Score (KPS) of 50-70 and 80-100 were in the expected direction, indicating that the module of questions is responsive to differing conditions. Patients with either mental confusion, motor deficit or dysphasia indicated problems in several domains and single items as compared to patients without these neurological deficits. Thus, differences in the responses to the items in the brain cancer module appear to reflect differences in neurological status. In addition, deteriorating neurological status was accompanied by a marked increase in emotional distress, future uncertainty and motor dysfunction. A comparison of the responses in the module with the KPS and with a modified Barthel Activities of Daily Living Index (BADLI) shows moderate correlations, primarily with scales and items that pertain to motor dysfunction, while other scales (such as emotional distress, visual disorder and communication deficit) and most single items are not associated with the KPS or BADLI. Since the emotional distress scale of the module was found to be highly correlated with the emotional function scale of the EORTC QLQ-C30, it could be omitted when the module is used in combination with the QLQ-C30. This would reduce the module to a total of 20 items with four scales and seven single items. The intention is to combine this module of questions with other core or general quality-of-life questionnaires when studying patients with brain cancer in clinical trials.