A COMPARISON OF 2 QUALITY-OF-LIFE QUESTIONNAIRES FOR CANCER CLINICAL-TRIALS - THE FUNCTIONAL LIVING INDEX-CANCER (FLIC) AND THE QUALITY-OF-LIFE QUESTIONNAIRE CORE MODULE (QLQ-C30)

Choosing a measuring instrument for a study raises the question of whe ther instruments designed for the same purpose produce the same result s. We investigated this question for two instruments designed to measu re subjective quality of life (QOL) in cancer clinical trials: the Fun ctional Living Index-Cancer (FLIC) and the Quality of Life Questionnai re Core module (QLQ-C30). These were administered concurrently to 98 c ancer patients. Four patient groups were defined: (1) well, no chemoth erapy (n = 23); (2) adjuvant chemotherapy (n = 24); (3) stable disease , active chemotherapy (n 24); (4) progressive disease (n = 27). Both i nstruments have global, role, social, emotional, pain, and nausea scal es; QLQ-C30 also assesses physical function, cognitive function, and f atigue, while FLIC assesses hardship. Correlation analysis indicated c onvergent validity for the global, role, emotional, pain, and nausea d imensions, but not the social dimension. Both instruments indicated th at groups 1 and 2 had better QOL than group 4 in at least one dimensio n. However, different dimension specific results meant that qualitativ ely different conclusions would have been drawn if either instrument h ad been used singly: FLIC indicated that group 1 had better role funct ion than group 4 and suffered less hardship and that group 1 suffered less nausea than group 3, while the QLQ-C30 data indicated that group 2 had better physical function than group 4. The only consistent resul t was for pain: both instruments indicated group 4 had more pain than either groups 1 or 2. Thus the choice of QOL instrument for use in a p articular trial will affect both the results and conclusions. It is im portant, therefore, to consider carefully which instrument is most lik ely to detect important differences relevant to the patients' lives in that setting.