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Minimally important difference for the Expanded Prostate Cancer Index Composite Short Form
Ted A Skolarus1, Rodney L Dunn2, Martin G Sanda3
1Department of Urology, Dow Division of Health Services Research, University of Michigan, Ann Arbor, MI; Division of Oncology, University of Michigan, Ann Arbor, MI; VA HSR&D Center for Clinical Management Research, VA Ann Arbor Healthcare System, Ann Arbor, MI.
This study defines clinically relevant changes for the Expanded Prostate Cancer Index Composite (EPIC-26) quality of life questionnaire. These minimally important differences (MIDs) help interpret symptom changes in prostate cancer survivors.
Area of Science:
- Oncology
- Health Outcomes Research
- Patient-Reported Outcomes
Background:
- The Expanded Prostate Cancer Index Composite (EPIC)-26 is a widely used patient-reported outcome measure for localized prostate cancer.
- Interpreting changes in quality of life scores requires established thresholds for clinical relevance.
- Minimally important differences (MIDs) provide these thresholds, aiding clinical and research applications.
Purpose of the Study:
- To establish score thresholds representing clinically relevant changes (MIDs) for each domain of the EPIC-26 questionnaire.
- To facilitate the clinical interpretation of quality of life changes in localized prostate cancer patients.
Main Methods:
- Employed both distribution- and anchor-based approaches to determine MID ranges.
- Utilized data from a prospective, multi-institutional cohort of 1201 men treated for prostate cancer.
- Followed patients for 3 years post-treatment, comparing EPIC-26 domain score changes to an overall cancer treatment satisfaction anchor.
Main Results:
- Established MID ranges for EPIC-26 domains: Bowel and vitality/hormonal (4-6 points), Sexual (10-12 points), Urinary incontinence (6-9 points), and Urinary irritation/obstruction (5-7 points).
- The sexual domain exhibited the largest MID values, indicating a greater score change is needed for clinical relevance.
- Bowel and vitality/hormonal domains showed the smallest MID ranges, suggesting smaller score changes are clinically meaningful.
Conclusions:
- Successfully established MIDs for all EPIC-26 domains using two independent methodologies.
- Defined MID values are crucial for researchers and clinicians to accurately assess clinically relevant changes in symptom burden among prostate cancer survivors.
