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J Clin Epidemiol. 2004 Sep;57(9):898-910.

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

Author information

  • 1Evanston Northwestern Healthcare and Northwestern University, Feinberg School of Medicine, 1001 University Place, suite 100, Evanston, IL 60201, USA. d-eton@northwestern.edu



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.


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.


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.


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.

[PubMed - indexed for MEDLINE]
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