Epidemiology

Breast Cancer Research and Treatment

, Volume 132, Issue 2, pp 729-739

First online:

Pre-diagnosis body mass index and survival after breast cancer in the After Breast Cancer Pooling Project

  • Marilyn L. KwanAffiliated withDivision of Research, Kaiser Permanente Email author 
  • , Wendy Y. ChenAffiliated withChanning Laboratory, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical SchoolDepartment of Medical Oncology, Dana-Farber Cancer Institute
  • , Candyce H. KroenkeAffiliated withDivision of Research, Kaiser Permanente
  • , Erin K. WeltzienAffiliated withDivision of Research, Kaiser Permanente
  • , Jeannette M. BeasleyAffiliated withFred Hutchinson Cancer Research Center
  • , Sarah J. NechutaAffiliated withDivision of Epidemiology, Department of Medicine, Vanderbilt University School of Medicine
  • , Elizabeth M. PooleAffiliated withChanning Laboratory, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School
  • , Wei LuAffiliated withShanghai Institute for Preventive Medicine
  • , Michelle D. HolmesAffiliated withChanning Laboratory, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School
    • , Charles P. QuesenberryJr.Affiliated withDivision of Research, Kaiser Permanente
    • , John P. PierceAffiliated withCancer Prevention and Control Program, Moores UCSD Cancer Center, University of California, San Diego
    • , Xiao Ou ShuAffiliated withDivision of Epidemiology, Department of Medicine, Vanderbilt University School of Medicine
    • , Bette J. CaanAffiliated withDivision of Research, Kaiser Permanente

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Abstract

Obese and underweight women who develop breast cancer may have poorer survival compared with normal-weight women. However, the optimal weight for best prognosis is still under study. We conducted a prospective investigation of pre-diagnosis body mass index (BMI) and mortality among 14,948 breast cancer patients in the After Breast Cancer Pooling Project. Breast cancer patients diagnosed from 1990 to 2006 with AJCC Stage I–III breast tumors were drawn from four prospective cohorts. Hazard ratios (HR) and 95% confidence intervals (CI) representing the associations of BMI categories (World Health Organization international classifications) with recurrence and mortality were estimated using delayed entry Cox proportional hazards models. Obese (30 to <35 kg/m2), severely obese (35 to <40 kg/m2), and morbidly obese (≥40 kg/m2) were examined. After a mean follow-up of 7.8 years, 2,140 deaths and 2,065 recurrences were documented. Both underweight (HR = 1.59; 95% CI: 1.18, 2.13) and morbidly obese women (HR = 1.81; 95% CI: 1.42, 2.32) had the greatest risk of overall mortality compared with normal weight (18.5–24.9 kg/m2) women. Severe obesity (HR = 1.09; 95% CI: 0.88, 1.36) and obesity (HR = 1.11; 95% CI: 0.97, 1.27) were related to small non-significant increased risks. Overweight (25.0–29.9 kg/m2) was not associated with any excess risk compared with normal weight. Similar associations were found for breast cancer death and non-breast cancer death but not recurrence. Women who were underweight and morbidly obese before breast cancer diagnosis were at the greatest risk of all-cause mortality. Morbidly obese women were also at increased risk of death from breast cancer. These results suggest that degree of obesity confers differential risk on survival.

Keywords

Body mass index Weight Obesity Breast cancer Survival Prognosis Mortality