The Validation of Functional Assessment of Cancer Therapy-Breast Symptom Index (FBSI) Among Iranian Women with Breast Cancer

 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.

 The study aimed at evaluating the validity of the functional assessment of cancer therapy-breast symptom index (FBSI-6 and -8) on Iranian patients.

 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.

 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.

 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.