Validation study of the Functional Assessment of Cancer Therapy-Cognitive Function-Version 3 for the Portuguese population

BACKGROUND: Cancer-related cognitive impairment is a common and potentially debilitating symptom experienced by patients with non-central nervous system (CNS) cancers, with negative impact on their quality of life. The Functional Assessment of Cancer Therapy-Cognitive Function-Version 3 (FACT-Cog-v3) is the most extensively used instrument specifically developed to evaluate cognitive complaints in adult cancer patients. Nevertheless, this self-report measure is not yet validated for the Portuguese population. Therefore, the purpose of this study was to evaluate the psychometric properties of the FACT-Cog-v3 among patients with non-CNS cancers in Portugal. METHODS: The validation study was conducted based on a convenience sample of 281 patients with non-CNS cancers, aged between 18 and 65 years, recruited online. A confirmatory factor analysis (CFA) was used to test the factor structure of the Portuguese FACT-Cog-v3 version; internal consistency analysis was also conducted. The European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core-30 (EORTC QLQ-C30–version 3) and the Hospital Anxiety and Depression Scale (HADS) were also used to test the concurrent, convergent, and discriminant validity of the scale. RESULTS: CFA supported a four-factor model with good fix indexes and internal consistencies: perceived cognitive impairments (α = 0.97), comments from others (α = 0.92), perceived cognitive abilities (α = 0.93), and impact on quality of life (α = 0.92). Concurrent, convergent, and discriminant validities were confirmed. Moderate and strong correlations were found between the FACT-Cog-v3 subscales and the QLQ-C30 cognitive functioning subscale. Good convergent validity, with moderate correlations, was found between the FACT-Cog-v3 subscales and the HADS-A, HADS-D, and QLQ-C30 fatigue, sleep disturbance, and global health status subscales. Acceptable discriminant validity, with weak and moderate correlations, was demonstrated between the FACT-Cog-v3 subscales and the QLQ-C30 pain and nausea/vomiting subscales. CONCLUSIONS: The Portuguese FACT-Cog-v3 version can be considered a reliable and valid measure to assess cognitive concerns of patients with non-CNS cancers, with relevance for research and clinical practice. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s40359-022-01018-w.