Development and psychometric properties of the Functional Assessment of Cancer Therapy-Cutaneous T-Cell Lymphoma (FACT-CTCL).

ABSTRACT

BACKGROUND: Patients with Mycosis Fungoides (MF)/Sézary Syndrome (SS) can experience impacted health-related quality of life (HRQoL). OBJECTIVES: To validate the CTCL-S, a novel subscale of the Functional Assessment of Cancer Therapy - General (FACT-G), in patients with MF/SS. METHODS: Qualitative interviews were conducted with expert clinicians and MF/SS patients. Thematic analysis identified the most common concerns, and 19 items were selected.MF/SS patients were recruited from a single center. FACT-G, CTCL-S (collectively "FACT-CTCL"), Skindex29, and Visual Analogue Scale-Pruritis (VAS itch) were administered. A subset repeated FACT-CTCL and VAS itch after ≈2 weeks. Patient demographics and clinical characteristics were obtained via review of the electronic medical record.Psychometric properties were assessed. Internal consistency was estimated using Cronbach's alpha (α). Convergent and discriminant validity were assessed by comparing CTCL-S to disease stage, age, VAS itch, FACT-G, and SkinDex29. Exploratory factor analysis (EFA) was used to preliminarily assess CTCL-S dimensionality. Test-retest repeatability was summarized using intraclass correlation coefficient (ICC), within-subject standard deviation (wSD), and within-subject coefficient of variation. RESULTS: Seventy-two patients completed the initial survey, and 35 repeated the FACT-CTCL and VAS itch after ≈2 weeks. Two-thirds were male, most were white (78%). The majority (85%) had MF, 15% SS, and 75% early (stage IA-IIA) and 25% advanced (≥ stage IIB) disease. Preliminary EFA found a single predominant factor, supporting a hypothesis of unidimensionality of the CTCL-S. Internal consistency of the CTCL-S was high (α 0.95 [95% CI 0.93-0.96]). There was no significant change in CTCL-S average test-retest scores (ICC of 0.93 (p = 0.63)). CTCL-S was significantly lower in advanced vs early stage disease (median[IQR] 34[26, 48] vs. 59[44, 68], p < 0.001) and strongly correlated with VAS itch (Spearman's r (rs) -0.70, 95% CI -0.81, -0.55), FACT-G (rs 0.77, 95% CI 0.65, 0.85), and Skindex29 (rs -0.90, 95% CI -0.94, -0.84), supporting convergent validity. CTCL-S scores had little correlation with age (rs 0.19, 95% CI -0.05, 0.41, p = 0.12), supporting discriminant validity. CONCLUSIONS: The FACT-CTCL is a disease specific instrument for assessing HRQoL with high reproducibility and good performance in a cohort of patients with MF/SS.