Elsevier

Value in Health

Volume 12, Issue 1, January–February 2009, Pages 124-129
Value in Health

Estimating Clinically Meaningful Changes for the Functional Assessment of Cancer Therapy—Prostate: Results from a Clinical Trial of Patients with Metastatic Hormone-Refractory Prostate Cancer

https://doi.org/10.1111/j.1524-4733.2008.00409.xGet rights and content
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Abstract

Objective

To determine clinically meaningful changes (CMCs) for the Functional Assessment of Cancer Therapy–Prostate (FACT–P).

Methods

We obtained data from a Phase III trial of atrasentan in metastatic hormone-refractory prostate cancer patients (n = 809). We determined anchor-based differences using Karnofsky Performance Status (KPS), bone alkaline phosphatase (BAP), hemoglobin, time to disease progression (TTP), adverse events (AE), and survival. One-third and one-half standard deviation and standard error of measurement (SEM) were used as distribution-based criteria for CMCs. Comparison across baseline FACT–P domains and derived scales [FACT–P total score, Trial Outcome Index (TOI) score, prostate cancer subscale (PCS) score, pain-related score, and FACT Advanced Prostate Symptom Index (FAPSI)] were conducted for KPS, BAP, and hemoglobin using Student's t tests. Twelve-week change scores were compared for TTP, AE, and survival using ANCOVA.

Results

CMCs were estimated as 6 to 10 for FACT–P total score, 5 to 9 for FACT–P TOI score, 2 to 3 for FACT–P PCS, 1 to 2 for the 4 PCS pain-related questions, and 2 to 3 for FAPSI. CMCs were also estimated using distribution-based criteria. Kappa statistics were computed to determine the degree of correspondence between the recommended guideline of 1.0 SEM and empirically derived standards. Most of the kappas for health-related quality of life domains and SEM standards had “substantial” to “almost perfect” concordance.

Conclusions

The significant relationship between clinical and quality of life data provides support for the use of CMCs to increase interpretability of FACT–P scores.

Keywords

clinically meaningful change
heath-related quality of life
minimally important difference
prostate cancer

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