Background: Our objective was to test a brief, symptom index for advanced renal cell carcinoma, a disease affecting over 38,000 Americans each year and often diagnosed in late stages.
Methods: We conducted secondary data analyses on patient-reported outcomes of 209 metastatic renal cell carcinoma patients participating in a Phase III clinical trial. Patient-reported outcomes, obtained from the FACT-Biological Response Modifier (FACT-BRM) scale, were available at baseline, 2, and 8 weeks. We analyzed data from eight FACT-BRM items previously identified by clinical experts to represent the most important symptoms of advanced renal cell carcinoma. Items comprising this index assess nausea, pain, appetite, perceived sickness, fatigue and weakness, with higher scores indicating fewer symptoms. We determined reliability and validity of the index and estimated a minimally important difference.
Results: The index had excellent internal reliability at all three time points (alphas > or = 0.83). Baseline scores were able to discriminate patients across Karnofsky performance status, number of metastatic sites, and risk group categories (ps < .01). Mean index scores declined over time likely indicative of the toxic nature of the administered treatments. Distribution- and anchor-based methods converged on a minimally important difference estimate of 2 to 3 points.
Conclusion: The 8-item index of patient-reported symptoms of renal cell carcinoma appears to be a psychometrically sound measure. It is a brief, reliable, and valid measure that can easily be adapted for use in clinical trials and observational studies.