Environment and Breast Cancer: Science Review

Evidence From Humans
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Obesity, tamoxifen use, and outcomes in women with estrogen receptor-positive early-stage breast cancer
Dignam, J. J., Wieand, K., Johnson, K. A., Fisher, B., Xu, L., Mamounas, E. P. Journal of the National Cancer Institute. 2003. 95:19, 1467-76.
Topic area
Body size
Study design
Prospective cohort
Funding agency
Not reported
Study Participants
Number of Cases
595 deaths following breast cancer events, 787 recurrences, 193 contralateral events, 983 overall deaths
Menopausal Status
The menopausal status of women included in this study is listed here.
Pre menopausal
Post menopausal
Number in Cohort
Cohort: 3,385 (1,035 premenopausal) (2,350 postmenopausal)
Cohort participation rate
Retention/participation exceeded 70% for exposed a
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
In: women enrolled in the National Surgical Adjuvant Breast and Bowel Project protocol B-14 (NSABP) between 1/82 and 10/88; did not have serious concomitant disease that would preclude treatment; had operable breast tumors that were ER-positive; axillary lymph nodes that were determined to be negative for tumor cells on histologic examinations
Comment about participation selection
Strengths: analyzed breast cancer mortality, total mortality, breast cancer recurrence, other second cancers and contralateral breast cancer by BMI; large number of patients; long follow-up duration which yielded adequate statistical power; restricted study to patients with operable tumors and negative axillary lymph nodes; one of the few studies to analyze breast cancer prognosis by systemic adjuvant therapy and BMI Limitations: small number of underweight women in study; did not acquire information pertaining to weight or obesity throughout different periods of life; lacked information on socioeconomic measures, dietary history, and other factors that could have contributed to obesity at the time of study entry; lacked longterm measurements of obesity during and after treatment; did not specify how anthropometric data were obtained
Exposure Investigated
Exposure assessment comment
Did not specify how anthropometric data was obtained
Statistical Analysis
Breast cancer outcome investigated
Breast cancer recurrence or progression
Mortality from breast cancer
Ethnic groups with separate analysis
If this study provided a separate analysis by ethnic or racial group, the groups are listed here.
Confounders considered
Other breast cancer risk factors, such as family history, age at first birth, and hormone replacement therapy use, that were taken into account in the study.
Adequately controlled, Confounders: treatment, age, menopausal status, race, tumor size, estrogen receptor status, progesterone receptor status
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked “Yes.” “No”, if not.
Description of major analysis
Follow-up: 13.8 years
Strength of associations reported
Contralateral breast cancer hazard increased with BMI, >30 vs 18.5-24.9, HR=1.58(1.10-2.25) trend p=0.04
Risk of breast cancer mortality increased with BMI, >30 vs 18.5-24.9, HR=1.20(0.97-1.49) trend p=0.36
Results Comments
Breast cancer mortality and recurrence was not significantly increased for obese women; Tamoxifen reduced breast cancer recurrence and mortality regardless of BMI
Author address
Department of Health Studies and Cancer Research Center, The University of Chicago, Chicago, IL 60637, USA. jdignam@health.bsd.uchicago.edu