Body mass index and survival in women with breast cancer-systematic literature review and meta-analysis of 82 follow-up studies.
BACKGROUND
Positive association between obesity and survival after breast cancer was demonstrated in previous meta-analyses of published data, but only the results for the comparison of obese versus non-obese was summarised.


METHODS
We systematically searched in MEDLINE and EMBASE for follow-up studies of breast cancer survivors with body mass index (BMI) before and after diagnosis, and total and cause-specific mortality until June 2013, as part of the World Cancer Research Fund Continuous Update Project. Random-effects meta-analyses were conducted to explore the magnitude and the shape of the associations.


RESULTS
Eighty-two studies, including 213 075 breast cancer survivors with 41 477 deaths (23 182 from breast cancer) were identified. For BMI before diagnosis, compared with normal weight women, the summary relative risks (RRs) of total mortality were 1.41 [95% confidence interval (CI) 1.29-1.53] for obese (BMI >30.0), 1.07 (95 CI 1.02-1.12) for overweight (BMI 25.0-<30.0) and 1.10 (95% CI 0.92-1.31) for underweight (BMI <18.5) women. For obese women, the summary RRs were 1.75 (95% CI 1.26-2.41) for pre-menopausal and 1.34 (95% CI 1.18-1.53) for post-menopausal breast cancer. For each 5 kg/m(2) increment of BMI before, <12 months after, and ≥12 months after diagnosis, increased risks of 17%, 11%, and 8% for total mortality, and 18%, 14%, and 29% for breast cancer mortality were observed, respectively.


CONCLUSIONS
Obesity is associated with poorer overall and breast cancer survival in pre- and post-menopausal breast cancer, regardless of when BMI is ascertained. Being overweight is also related to a higher risk of mortality. Randomised clinical trials are needed to test interventions for weight loss and maintenance on survival in women with breast cancer.
Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, London, UK. Electronic address: d.chan@imperial.ac.uk.
D S M
DSM
Chan
Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, London, UK.
A R
AR
Vieira
Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, London, UK; Department of Public Health and General Practice, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
D
D
Aune
Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Jersey, USA.
E V
EV
Bandera
Division of Biostatistics, Centre for Epidemiology and Biostatistics, University of Leeds, Leeds, UK.
D C
DC
Greenwood
Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Washington, USA.
A
A
McTiernan
Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, London, UK.
D
D
Navarro Rosenblatt
Department of Oncology, Oslo University Hospital, Oslo; Faculty of Health Sciences, Department of Community Medicine, University of Tromso, Tromso, Norway.
I
I
Thune
School of Mathematics and Statistics, University of Newcastle, Newcastle upon Tyne, UK.
R
R
Vieira
Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, London, UK.
T
T
Norat
D015992:Body Mass Index; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000473:pathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016239:MEDLINE; D009765:Obesity / Q000150:complications / Q000453:epidemiology*; D011379:Prognosis; D016032:Randomized Controlled Trials as Topic; D012307:Risk Factors; D017741:Survivors
body mass index; meta-analysis; survival after breast cancer; systematic literature review