Minimally important differences were estimated for the Functional Assessment of Cancer Therapy-Colorectal (FACT-C) instrument using a combination of distribution- and anchor-based approaches

K. J. Yost*, D. Cella, A. Chawla, E. Holmgren, D. T. Eton, J. Z. Ayanian, D. W. West

*Corresponding author for this work

Research output: Contribution to journalArticle

114 Scopus citations

Abstract

Objective: To estimate minimally important differences (MIDs) on the Functional Assessment of Cancer Therapy-Colorectal (FACT-C) instrument using anchor- and distribution-based methods. Study Design and Setting: Preliminary MIDs were generated for FACT-C scores based on published results for two samples (n = 60 and n = 63) from the FACT-C validation study. Preliminary MIDs were confirmed using data from a Phase II randomized controlled clinical trial (n = 104) and a population-based observational study (n = 568). MIDs were estimated for the colorectal cancer subscale (CCS); the FACT-C Trial Outcome Index (TOI-C), which is the sum of the CCS, physical well-being, and functional well-being subscales; and the FACT-C total score. Both cross-sectional and longitudinal analyses were used. Results: MIDs were stable across the different patient samples. The recommended MIDs ranged from 2 to 3 points for the CCS, 4 to 6 points for the TOI-C, and 5 to 8 points for the FACT-C total score. Conclusions: MIDs can enhance the interpretability of FACT-C scores, and they can be used to provide a basis for sample size estimation and to determine clinical benefit in combination with other measures of efficacy. General guidelines for estimating MIDs for other FACT instruments are suggested.

Original languageEnglish (US)
Pages (from-to)1241-1251
Number of pages11
JournalJournal of Clinical Epidemiology
Volume58
Issue number12
DOIs
StatePublished - Dec 1 2005

Keywords

  • Clinical significance
  • Colorectal cancer
  • Health-related quality of life
  • Minimally important difference

ASJC Scopus subject areas

  • Epidemiology

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