Effects of weight loss on weight and cardiorespiratory fitness in overweight or obese breast cancer survivors

OF THE THESIS Effects of Weight Loss on Weight and Cardiorespiratory Fitness in Overweight or Obese Breast Cancer Survivors by Lorena Sonia Pacheco Master of Public Health with a Concentration in Epidemiology San Diego State University, 2012 Breast cancer is the most common invasive cancer among women in developed countries. Due to earlier detection and better initial treatments, the number of breast cancer survivors has increased, and cancer recurrence is of concern for this population. Factors affecting survival include obesity and physical inactivity, with a higher risk of dying from breast cancer if a survivor is obese. Limited investigations have addressed the effect of weight loss among breast cancer survivors. The purposes of this study are to examine the effects of a cognitive behavioral therapy (CBT) weight loss intervention on weight change and of cardiorespiratory fitness (CRF) in the Survivor’s Health And Physical Exercise (SHAPE) Study. The target population was female breast cancer survivors in San Diego who met the appropriate criteria, including a body mass index >25.0 kg/m and a history of invasive breast cancer. Participants (N=258) were randomly assigned to one of two groups, treatment or wait-list control, and followed from baseline to 18 months. The intervention consisted of semi-structured group sessions combining CBT, increased physical activity, and dietary guidance to promote weight loss. Weight and CRF measurements, including VO2max estimated from workload, and total treadmill time, were obtained at baseline, 6 and 18 months. Study participants, with mean age 55(9.4) years, had an average weight of 84.8(15.0) kg and average CRF of 25.5(6.3) ml/kg/min, and 8.6 (3.3) minutes, at baseline. The women were mainly non-Hispanic white (83.7%), with 13-16 years of education (58.2%), married (68.2%), employed full-time (44.1%), diagnosed with Stage I breast cancer (45.4%), and had been treated with a combination of surgery, radiation and chemotherapy (49.4%). Univariate and bivariate statistics, including Pearson correlations, t-tests and analysis of variance (ANOVA), were used to identify associations and differences. Significant weight loss of 4.5(4.7) (p<0.0001) and 3.8(5.2) (p=0.003) kg, at 6 and 18 months from baseline, respectively, was seen in the intervention group. Repeated measures analysis was employed to determine time series changes. Results for weight showed a significant group and time interaction, with a decrease in weight for those women in the intervention group at both 6 (4.08 kg loss, p<0.001) and 18 (2.14 kg loss, p<0.01) months from baseline. CRF results, for both estimated VO2max and total treadmill time, were marginally significant at 6 months (1.40 mL/kg/min and 0.70 minutes) (p<0.10), but were significant at 18 months (2.25 mL/kg/min and 1.27 minutes) (p<0.05). Greater weight loss effects were observed at 6 and 18 months while improved CRF effects were observed at 18 months. This study provides knowledge of how the CBT-based weight loss intervention can be successful for this population, which may affect risk for cancer recurrence and survival.