RESUMEN
BACKGROUND: The objective of this study was to investigate the relationship of aerobic fitness (AF) at diagnosis, before treatment and its relationship with body composition, physical function, lipidic profile, comorbidities, tumor characteristics, and quality of life of women with breast cancer (BC) PATIENTS AND METHODS: This cross-sectional cohort study included 78 women with BC that were assessed before treatment. A 6-minute walk test was used to evaluate the subjects' AF, estimating the maximum oxygen consumption (VO2max) to classify the women with BC into 2 groups: good/excellent AF or fair/weak/very weak AF. Dual-energy x-ray absorptiometry was performed to assess body composition. The International Global Physical Activity Questionnaire and the Functional Assessment of Cancer Therapy - Fatigue questionnaires were applied to assess the level of physical activity and the quality of life, respectively. RESULTS: Among the women included, the majority (81%) had the luminal subtype of BC. Most of the women were diagnosed with T1/T2 tumors and with negative axillary lymph nodes. We found that women with BC with good/excellent AF (VO2max = 32.9 ± 6.0 mL/kg/min-1) presented significantly lower weight, body mass index, abdominal circumference, percentual and total body fat, and bone mineral density compared with women with fair/weak/very weak AF (VO2max = 21.8 ± 6.9 mL/kg/min-1). Also, women with BC with good/excellent AF showed better performance on physical functional tests. No relationship between estimated VO2max and comorbidities, tumor characteristics, or quality of life was found. CONCLUSION: AF is a predictor of body composition and physical function in women with BC. These data suggest that women with BC with higher AF can decrease the chance of adverse effects during BC treatment.