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Effect of body mass index on tumor characteristics and disease‐free survival in patients from the HER2‐positive adjuvant trastuzumab trial N9831
Author(s) -
Crozier Jennifer A.,
MorenoAspitia Alvaro,
Ballman Karla V.,
Dueck Amylou C.,
Pockaj Barbara A.,
Perez Edith A.
Publication year - 2013
Publication title -
cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.052
H-Index - 304
eISSN - 1097-0142
pISSN - 0008-543X
DOI - 10.1002/cncr.28051
Subject(s) - medicine , hazard ratio , overweight , body mass index , confidence interval , breast cancer , trastuzumab , proportional hazards model , oncology , cancer
BACKGROUND Data suggest that weight, and specifically body mass index (BMI), plays a role in breast cancer development and outcome. The authors hypothesized that there would be a correlation between BMI and clinical outcome in patients with early stage, human epidermal receptor 2 (HER2)‐positive breast cancer enrolled in the N9831 adjuvant trial. METHODS Patients were grouped according to baseline BMI as follows: normal (BMI <25 kg/m 2 ), overweight (BMI ≥25 kg/m 2 and <30 kg/m 2 ), and obese (BMI ≥30 kg/m 2 ). Disease‐free survival (DFS) was estimated using the Kaplan‐Meier method. Comparisons between treatment arms A, B, and C (chemotherapy with or without trastuzumab) were performed using a stratified Cox proportional hazards model. RESULTS Analysis was completed on 3017 eligible patients. Obese patients were more likely to be older and postmenopausal ( P < .0001 for both), to have larger tumors ( P = .002), and to have positive lymph nodes ( P = .004). In the pooled analysis cohort, differences in DFS among the BMI groups were statistically significant (5‐year DFS rate: 82.5%, 78.6%, and 78.5% for normal weight, overweight, and obese women, respectively; log‐rank P = .02). The adjusted hazard ratio comparing the DFS of overweight women with the DFS of normal women was 1.30 (95% confidence interval, 1.06‐1.61); and, comparing the DFS of obese women with the DFS normal women, the adjusted hazard ratio was 1.31 (95% confidence interval, 1.07‐1.59). There were no statistically significant differences in DFS by weight group for women within any trial arm. CONCLUSIONS Patients with early stage, HER2‐positive breast cancer and normal BMI had a better 5‐year DFS compared with overweight and obese women. The current results indicated that adjuvant trastuzumab improves clinical outcome regardless of BMI. Cancer 2013;119:2447‐2454 . © 2013 American Cancer Society .