RESUMO
PURPOSE: To analyze longitudinal changes in each subscale of a quality of life (QOL) measure and to explore their relationships to effective QOL predictors in breast cancer surgery patients. PATIENTS AND METHODS: This prospective study analyzed 172 patients at two tertiary academic hospitals. All patients completed the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30) and its supplementary breast cancer measure (QLQ-BR23) at baseline and at 1 and 2 years postoperatively. The 95% confidence intervals for differences in responsiveness estimates were derived by bootstrap estimation. Scores derived by these instruments were interpreted by generalized estimating equation (GEE) before and after surgery. RESULTS: A 2-year follow-up survey of the examined population revealed significant (P < 0.05) improvement in each QOL subscale. In both postoperative surveys, effect size was largest in the QLQ subscales for patients who had received mastectomy with reconstruction and lowest in those who had received modified radical mastectomy. After adjusting for time effects and baseline predictors, GEE approaches revealed the following explanatory variables for QOL: time, type of surgical procedure, age, chemotherapy, radiotherapy, hormone therapy, and preoperative functional status. CONCLUSIONS: When evaluating QOL after breast cancer surgery, several factors other than the surgery itself should be considered. Patients should also be advised that their postoperative QOL might depend not only on the success of their operations, but also on their preoperative functional status.