Value of caregiver ratings in evaluating the quality of life of patients with cancer.

Purpose: To evaluate the usefulness of caregiver ratings of cancer patients' quality of life (QL), we examined the following: (1) the comparability of responses to a brief standardized QL questionnaire provided by patients, physicians, and informal caregivers; and (2) the relative validity of these ratings.
Methods: The study sample included cancer patients receiving chemotherapy, their treating physicians, and significant others involved closely in the (informal) care of the patients. During an early phase of treatment and 3 months later, patients and caregivers completed independently the COOP/WONCA charts, covering seven QL domains. At baseline, all sources of information were available for 295 of 320 participating patients (92%). Complete follow-up data were obtained for 189 patient-caregiver triads.
Results: Comparison of mean scores on the COOP/WONCA charts revealed close agreement between patient and caregiver ratings. At the individual patient level, exact or global agreement was observed in the majority of cases (73% to 91%). Corrected for chance agreement, moderate intraclass correlations (ICC) were noted (0.32 to 0.72). Patient, physician, and informal caregiver COOP/WONCA scores were all responsive to changes over time in specific QL domains, but differed in their relative performance. Relative to the patients, the physicians were more efficient in detecting changes over time in physical fitness and overall health, but less so in relation to social function and pain.
Conclusion: For studies among patient populations at risk of deteriorating self-report capabilities, physicians and informal caregivers can be useful as alternative or complementary sources of information on cancer patients' QL.