Measuring health status in patients with skeletal metastases treated by surgery

Since the introduction of the Functional Living Index-Cancer (FLIC) > 10 years ago, a variety of general as well as disease-specific quality of life (QOL) instruments have been developed and used as a means of assessing the success of clinical interventions. Clinicians faced with selecting an appropriate QOL measurement tool will need guidance in both the selection of the instrument and its evaluation for applicability to the patient group under study. In our examination of this issue, we analyzed the results of administering the FLIC and the more general SF-36 questionnaire to a group of 17 patients who had undergone orthopaedic surgery to correct problems associated with bone metastatic cancer. Because the SF-36 has been widely adopted as a general Health Status evaluation tool and because of its extensive validation it may be considered a gold standard providing a means of assessing the validity of disease-specific instruments such as the FLIC. Using multivariate regression, we built a model in which five of the eight health status dimensions of the SF-36 account for 77% of the variation in the FLIC scores for this group of patients (R2 = 0.77). The implication of this result is that most of the information (i.e., 77%) provided by the FLIC could be equivalently obtained using the more general, more widely validated SF-36. Despite the small sample size, half of the regression coefficients in this model achieved a high level of statistical significance (p < 0.001). In addition, when applied to new patients, the model showed good predictive capability with relative error 2-20%. If these results can be replicated for other patient disease groups and in larger study populations, it may be possible to use the SF-36 as the primary QOL evaluation tool for cancer patients. The burden of this disease could then be more easily compared with that of other disease groups and the resulting standardization of QOL analysis would be simpler and more cost effective.