The validation of functional assessment of cancer therapy-breast symptom index (FBSI) among Iranian women with breast cancer

Abstract

Background: Patient-reported outcomes (PROs) are widely utilized in research and clinical practice. The functional assessment of cancer therapy-breast cancer (FACT-B) provides effective indexes addressing different dimensions of quality of life (QoL) in patients with breast cancer. Objectives: The study aimed at evaluating the validity of the functional assessment of cancer therapy-breast symptom index (FBSI-6 and-8) on Iranian patients. Methods: Overall, 223 patients from three cancer centers participated in the present study. Internal consistency was assessed via Cronbach’s alpha and inter-item correlations. Spearman’s rho correlation was utilized to evaluate convergent/divergent validity and performance of the target indexes in terms of psychosocial distress, compared to trial outcome index-physical/functional/breast (TOI-PFB), as well as TOI emotional/social/breast (TOI-ESB) cancer subscales. The known-groups analysis, using Mann-Whitney U and Kruskal-Wallis tests, was conducted based on the history of metastasis, chemotherapy, radiotherapy, mastectomy, and time since diagnosis. P value < 05 was considered significant. Results: Both of the target indexes showed acceptable internal consistency. They were highly correlated with physical wellbeing and TOI-PFB, moderately with functional wellbeing and breast cancer subscale, lowly with the arm subscale, and very lowly with social wellbeing (P < 0.0001). All indexes showed significant and negative correlations with distress symptoms (P < 0.0001). The FBSI-8 slightly outperformed FBSI-6 in terms of distress symptoms. No significant differences were seen in the target indexes based on clinical characteristics, including metastasis, chemotherapy, radiotherapy, mastectomy surgery, and time since diagnosis. Conclusions: The current study confirmed the validity of FBSI-6 and-8 among Iranian women with breast cancer. Further research is required to evaluate the more profound properties of FBSI.