title: Pre-diagnosis body mass index and survival after breast cancer in the After Breast Cancer Pooling Project.
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/m(2)), severely obese (35 to < 40 kg/m(2)), and morbidly obese (≥ 40 kg/m(2)) 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/m(2)) 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/m(2)) 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.
authors.affiliation: Division of Research, Kaiser Permanente, 2000 Broadway, Oakland, CA 94612, USA. Marilyn.L.Kwan@kp.org
authors.forename: Marilyn L
authors.initials: ML
authors.lastname: Kwan
authors.forename: Wendy Y
authors.initials: WY
authors.lastname: Chen
authors.forename: Candyce H
authors.initials: CH
authors.lastname: Kroenke
authors.forename: Erin K
authors.initials: EK
authors.lastname: Weltzien
authors.forename: Jeannette M
authors.initials: JM
authors.lastname: Beasley
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Nechuta
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Poole
authors.forename: Wei
authors.initials: W
authors.lastname: Lu
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Holmes
authors.forename: Charles P
authors.initials: CP
authors.lastname: Quesenberry
authors.forename: John P
authors.initials: JP
authors.lastname: Pierce
authors.forename: Xiao Ou
authors.initials: XO
authors.lastname: Shu
authors.forename: Bette J
authors.initials: BJ
authors.lastname: Caan
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D001943:Breast Neoplasms / Q000175:diagnosis / Q000401:mortality* / Q000556:secondary; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D008875:Middle Aged; D015999:Multivariate Analysis; D009364:Neoplasm Recurrence, Local; D009367:Neoplasm Staging; D009765:Obesity / Q000175:diagnosis / Q000401:mortality*; D009767:Obesity, Morbid / Q000175:diagnosis / Q000401:mortality; D011379:Prognosis; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012044:Regression Analysis; D018570:Risk Assessment; D012307:Risk Factors; D012720:Severity of Illness Index; D016019:Survival Analysis; D017741:Survivors / Q000706:statistics & numerical data*; D013851:Thinness / Q000175:diagnosis / Q000401:mortality*; D013997:Time Factors; D014481:United States / Q000453:epidemiology