Validity, reliability and understanding of the EORTC-C30 and EORTC-BR23, quality of life questionnaires specific for breast cancer

Abstract

Objective: To validate and assess reliability and understanding of the EORTC–C30 quality of life questionnaire and its breast cancer specific module, the EORTC-BR23. Methods: This study was conducted at the AC Camargo Cancer Hospital, São Paulo, Brazil. A total of 100 women diagnosed with breast cancer were interviewed. Internal consistency, confirmatory factorial analysis, convergent validity, construct validity and degree of understanding were examined. Reliability was assessed by comparison of means at times 1 and 2, inter-class coefficient and Bland-Altman graphics. Results: Cronbach’s alpha ranged from 0.72 to 0.86 for the EORTC-C30 and from 0.78 to 0.83 for the EORTC-BR23 questionnaire. Most questions were confirmed in the confirmatory factorial analysis. In the construct validity analysis, the questionnaires were capable of differentiating patients with or without lymphedema, apart from the symptom scales of both questionnaires. Both questionnaires presented a significant correlation in most domains of the SF-36, in the convergent validity analysis. Only a few criticisms were reported concerning questions, and the mean grade of understanding was high (C30 = 4.91 and BR23 = 4.89). The questionnaires presented good rates of reliability, with the exception of the functional scale of the C30 and the symptom scale of the BR23. Conclusions: The EORTC-C30 and EORTC-BR23 quality of life questionnaires were validated, presented good rates of reliability and are easily understood, allowing them to be used in Brazil to assess quality of life among women with breast cancer.