Comprehensive Validation Study of Quality-of-Life Questionnaire Using Objective Clinical Measures: Breast Cancer Treatment Outcome Scale (BCTOS), Brazilian Portuguese Version.

INTRODUCTION: When evaluating a quality-of-life questionnaire (QLQ), many validation studies do not correlate quality-of-life scores with objective measurements of complications associated with treatment. PATIENTS AND METHODS: We performed a cross-sectional observational study with 300 patients submitted to breast-conserving therapy. The patients answered the European Organization for Research and Treatment of Cancer (EORTC) QLQs C-30 and BR23, as well as the Brazilian Portuguese version of the Breast Cancer Treatment Outcome Scale (BCTOS) questionnaire. Retest, internal consistency, factorial analysis, convergent/divergent analysis, and Rasch evaluation were performed. All patients underwent physical evaluations to assess lymphedema, handgrip strength, shoulder range of motion, breast cosmesis, and breast pain, and these groups were compared on the basis of BCTOS scores. Receiver operating characteristic curve determined the predictive value of BCTOS scores associated with clinical practice. RESULTS: The internal consistencies of the BCTOS domains ranged from 0.785 to 0.895. Factor analysis grouped according to the original questionnaire. Convergent validation showed differences in the sexual functioning and sexual enjoyment domains of the EORTC BR23. Analysis of known groups found that in most domains, the scores were higher in patients with lymphedema, strength deficit, shoulder range-of-motion alteration, poor breast cosmesis, breast pain, and axillary lymphadenectomy. Using a cutoff of 1.26, lymphedema was associated with the edema domain; using a cutoff of 1.33, Late Effects Normal Tissue Task Force/Subjective, Objective, Management, Analytic pain was associated with the pain domain; and using a cutoff of 2.37, the cosmetic domain was associated with subjective cosmesis. CONCLUSION: The association of objective measurements in a validation study of quality of life qualified the study and allowed us to develop better parameters for comparisons of results of breast-conserving therapy between populations.