Objective: To examine the test-retest reliability of the Functional Assessment of Cancer Therapy - 8 Dimension (FACT-8D) for the first time, and to conduct a head-to-head comparison of the distribution properties and validity between the FACT-8D and EQ-5D-5L in Colorectal Cancer (CRC) Patients.
Methods: We conducted a longitudinal study on Chinese CRC patients, employing Functional Assessment of Cancer Therapy-General (FACT-G) and EQ-5D-5L at baseline, and FACT-G during follow-up (2-7 days from baseline). Utility scores for FACT-8D were derived from all available value sets (Australia, Canada and USA), while EQ-5D-5L scores were obtained from corresponding value sets for various countries. We assessed convergent validity using pairwise polychoric correlations between the FACT-8D and EQ-5D-5L; known-groups validity by discriminating participants' clinical characteristics, and effect size (ES) was tested; test-retest reliability for FACT-8D using kappa and weighted Kappa for choice consistency, and intraclass correlation coefficient (ICC) and Bland-Altman method for utility consistency.
Results: Among the 287 patients with CRC at baseline, 131 were included in the retest analysis. The utility scores of FACT-8D were highly positively correlated with EQ-5D-5L across various country value sets (r = 0.65-0.77), and most of the dimensions of FACT-8D and EQ-5D-5L were positively correlated. EQ-5D-5L failed to discriminate known-groups in cancer stage across all value sets, whereas both were significant in FACT-8D (ES = 0.35-0.48, ES = 0.38-0.52). FACT-8D showed good test-retest reliability (Cohen's weighted Kappa = 0.494-0.722, ICC = 0.748-0.786).
Conclusion: The FACT-8D can be used as a valid and reliable instrument for clinical evaluation of patients with CRC, outperforming EQ-5D-5L in differentiating clinical subgroups and showing promise for cancer practice and research.
Keywords: Cancer-specific multi-attribute utility instrument; Colorectal cancer patients; FACT-8D; Reliability; Validity.
Recently, the Multi-Attribute Utility in Cancer Consortium developed the Functional Assessment of Cancer Therapy − 8 Dimension (FACT-8D), a new cancer-specific multi-attribute utility instrument based on the Functional Assessment of Cancer Therapy - General (FACT-G). This addresses the FACT-G’s limitation in directly generating utility values, which has broad application prospects in cost-utility analysis within the field of oncology. To our knowledge, this is the first study to examine the test-retest reliability of FACT-8D and to conduct a head-to-head comparison of its distribution properties and validity against the EQ-5D-5L in colorectal cancer (CRC) patients. The results indicate that FACT-8D is a valid and reliable instrument for clinical evaluation of CRC patients, demonstrating superior performance in differentiating between known clinical groups compared to the generic MAUI EQ-5D-5L, and is a promising instrument for use in cancer practice and research.
© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.