Validation of the Functional Assessment of Cancer Therapy-Breast Symptom Index (FBSI)

Abstract

We assessed the reliability, validity, and responsiveness to change of the 6-item Functional Assessment of Cancer Therapy-Breast Symptom Index (FBSI) in a sample of 615 metastatic breast cancer patients. The FBSI is a brief, clinically relevant, and psychometrically sound instrument that can be used to measure symptoms in patients with breast cancer.

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

“…Because it may in some cases overestimate the true MID, this guideline (1/2 SD) may be most appropriate in situations where instrument-specific MID data are lacking. To date, 8 studies have been conducted to identify the MID on 17 scales and subscales (excluding the 3 in the present study) in the FA-CIT measurement system [29][30][31][32][33][34]41,42]. These studies provide evidence that MIDs for FACIT instruments are fairly stable across patient populations.…”

“…For example, recommended MIDs are 2-3 points for the 7-item CCS (0.29-0.43 points per item), 4-6 points for the 21-item TOI-C (0.19-0.29 points per item), and 5-8 points for the 34-item FACT-C (0.15-0.24 points per item). Based on the 17 MIDs from the previous 8 studies [29][30][31][32][33][34]41,42] and the 3 MIDs from the present study, MIDs for disease-, treatment-and symptom-specific subscales for FACIT instruments consistently fall in the range of approximately 0.30-0.40 points per item, MIDs for TOIs are consistently 0.20-0.30 points per item, and MIDs for total scores of various FACT instruments consistently fall in the range of approximately 0.15-0.25 points per item. By comparison, Juniper, Guyatt and colleagues have suggested 0.5 points per item [43]; however, they use 7-point scales.…”

“…We use the term minimally important difference (MID), which has been defined as the ''smallest difference in score in the domain of interest that patients perceive as important, either beneficial or harmful, and that would lead the clinician to consider a change in the patient's management'' [23, p. 377]. MIDs for scales and subscales from the Functional Assessment of Chronic Illness Therapy (FACIT) measurement system [8] have been identified using distribution-and anchor-based methods for non-small cell lung cancer [29], fatigue or anemia [30,31], and most recently breast cancer [32,33] and biological response modifiers [34].…”

Priority Symptoms in Advanced Breast Cancer: Development and Initial Validation of the National Comprehensive Cancer Network-Functional Assessment of Cancer Therapy-Breast Cancer Symptom Index (NFBSI-16)

“…We modeled our methodology after the NCCN clinician survey used to develop the original 8-item FBSI [34,35] to evaluate the concordance between patient and clinician priority symptoms and to select those endorsed most frequently by both parties for the new 16-item version (NFBSI-16). Priority symptoms were assessed in two complementary ways: patient-generated concerns and patient ratings of candidate FACIT items.…”

“…The FBSI was also informed by results of a comprehensive survey of National Comprehensive Cancer Network (NCCN) physician and nurse experts who identified priority symptoms and concerns in evaluating treatments for advanced breast cancer [34]. The FBSI demonstrates acceptable reliability and validity and has an identified minimally important difference score (2-3 points) to better interpret scores [35].…”