Psychometric evaluation of the FACT colorectal cancer symptom index (FCSI-9): Reliability, validity, responsiveness, and clinical meaningfulness

Background. Patient-reported outcomes (PROs) are essential for evaluating treatment effects on health-related quality of life and symptoms from the patient's perspective. This study sought to evaluate the psychometric properties of the nine-item Functional Assessment of Cancer Therapy/National Comprehensive Cancer Network Colorectal Cancer Symptom Index (FCSI-9) in a metastatic colorectal cancer (mCRC) population. Methods. The FCSI-9 and EQ-5D were administered every 2-4 weeks to mCRC subjects in a phase III clini-cal trial. Three hundred ninety-one mCRC subjects completed the questionnaires at baseline and at least one follow-up assessment. Internal consistency reliability, test-retest reliability, construct validity, known groups validity, responsiveness, and the minimum im-portant difference (MID) of the FCSI-9 were evaluated. Results. The internal consistency and test-retest reliability of the FCSI-9 were acceptable (0.81 and 0.76, re-spectively). Construct validity was supported based on moderatecorrelationswiththeEQ-5D.Knowngroupsva-lidity was evaluated by examining the FCSI-9 scores of subjects categorized by their Eastern Cooperative Oncology Group performance status (PS) score. Subjects with better PS scores reported significantly higher FCSI-9 scores than those with lower PS scores at both baseline and week8.Responsiveness, as measured by Guyatt'sstatistic, was 0.77 from baseline to week 8 and 0.60 from week 4 to week 12. Considering all data together, the MID of the FCSI-9 is estimated to be in the range of 1.5-3.0 points. Conclusion. Results provide preliminary evidence of the reliability, validity, and responsiveness of the FCSI-9.