Journal
INTERNATIONAL JOURNAL OF EPIDEMIOLOGY
Volume 47, Issue 3, Pages 987-997Publisher
OXFORD UNIV PRESS
DOI: 10.1093/ije/dyy039
Keywords
BMI; body size; breast cancer; BRCA; hereditary cancer
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Funding
- Canadian Gene Cure Foundation
- Canadian Institutes of Health Research (CIHR) Institute of Genetics
- Canadian Cancer Society Research Institute [703058]
- American Cancer Society Clinical Research Professorship [SIOP-06-258-01-COUN]
- Morris and Horowitz Families Endowed Professorship
- Canada Research Chair tier I
- Cancer Care Ontario Research Chair in Population Studies
- Canadian Cancer Society Career Development Award in Prevention
- Charles F. and Mary C. Heider Chair in Cancer Research, Creighton University
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Background: Although evidence suggests that larger body size in early life confers lifelong protection from developing breast cancer, few studies have investigated the relationship between body size and breast cancer risk among BRCA mutation carriers. Therefore, we conducted a prospective evaluation of body size and the risk of breast cancer among BRCA mutation carriers. Methods: Current height and body mass index (BMI) at age 18 were determined from baseline questionnaires. Current BMI and weight change since age 18 were calculated from updated biennial follow-up questionnaires. Cox proportional hazards models were used to estimate the hazard ratio (HR) and 95% confidence interval (CI). Results: Among 3734 BRCA mutation carriers, there were 338 incident breast cancers over a mean follow-up of 5.5 years. There was no association between height, current BMI or weight change and breast cancer risk. Women with BMI at age 18 >= 22.1 kg/m(2) had a decreased risk of developing post-menopausal breast cancer compared with women with a BMI at age 18 between 18.8 and 20.3 kg/m(2) (HR 0.49; 95% CI 0.30-0.82; P = 0.006). BMI at age 18 was not associated with risk of pre-menopausal breast cancer. Conclusions: There was no observed association between height, current BMI and weight change and risk of breast cancer. The inverse relationship between greater BMI at age 18 and post-menopausal breast cancer further supports a role of early rather than current or adulthood exposures for BRCA-associated breast cancer development. Future studies with longer follow-up and additional measures of adiposity are necessary to confirm these findings.
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