A combination of distribution- and anchor-based approaches determined minimally important differences (MIDs) for four endpoints in a breast cancer scale

J Clin Epidemiol. 2004 Sep;57(9):898-910. doi: 10.1016/j.jclinepi.2004.01.012.


Objective: To determine distribution- and anchor-based minimal important difference (MID) estimates for four scores from the Functional Assessment of Cancer Therapy-Breast (FACT-B): the breast cancer subscale (BCS), Trial Outcome Index (TOI), FACT-G (the general version), and FACT-B.

Study design and setting: We used data from a Phase III clinical trial in metastatic breast cancer (ECOG study 1193; n=739) and a prospective observational study of pain in metastatic breast cancer (n=129). One third and one half of the standard deviation and 1 standard error of measurement were used as distribution-based criteria. Clinical indicators used to determine anchor-based differences included ECOG performance status, current pain, and response to treatment.

Results: FACT-B scores were responsive to performance status and pain anchors, but not to treatment response. By combining the results of distribution- and anchor-based methods, MID estimates were obtained: BCS=2-3 points, TOI=5-6 points, FACT-G=5-6 points, and FACT-B=7-8 points.

Conclusion: Distribution- and anchor-based estimates of the MID do show convergence. These estimates can be used in combination with other measures of efficacy to determine meaningful benefit and provide a basis for sample size estimation in clinical trials.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Breast Neoplasms / drug therapy
  • Breast Neoplasms / rehabilitation*
  • Clinical Trials, Phase III as Topic
  • Epidemiologic Methods
  • Female
  • Health Status Indicators*
  • Humans
  • Middle Aged
  • Neoplasm Metastasis
  • Pain Measurement / methods
  • Quality of Life*
  • Treatment Outcome