Environment and Breast Cancer: Science Review

Evidence From Humans
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Fasting insulin and outcome in early-stage breast cancer: results of a prospective cohort study
Goodwin, P. J., Ennis, M., Pritchard, K. I., Trudeau, M. E., Koo, J., Madarnas, Y., Hartwick, W., Hoffman, B., Hood, N. Journal of Clinical Oncology. 2002. 20:1, 42-51.
Topic area
Body size
Study design
Prospective cohort
Funding agency
Other: Canadian Breast Cancer Research Initiative
Study Participants
Number of Cases
118 (76 recurrences) (42 deaths)
Menopausal Status
The menopausal status of women included in this study is listed here.
Pre menopausal
Post menopausal
Number in Cohort
Cohort: 512 (289 pre) (26 peri) (197 post)
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
In: underwent treatment for operable breast cancer at three University of Toronto hospitals between 7/89 and 6/96; less than 75 years of age; received a complete resection; underwent axillary node dissection for previously untreated T1 to T3, N0 to N1, M0 breast cancer Ex: prior malignancy; serious coexisting medical condition, including diabetes I or II; use of medications that could influence key study variables; inability to speak English; refused to provide informed consent
Comment about participation selection
Strengths: anthropometric data were measured by trained staff; participants completed the Block Food Frequency Questionnaire; pathology reports were reviewed prospectively; Insulin and hormone receptors were measured; prospective study; research personnel were blinded to insulin assay results; tumor stage, ER and PR status were noted; analyzed breast cancer recurrence and death by BMI; one of the first studies to analyze the prognostic effect of insulin on breast cancer Limitations: baseline measurements were performed after diagnosis and operation; low participation rate (56%); few recurrences and breast cancer mortalities; possibility that participants had undiagnosed diabetes
How exposure was measured
Questionnaire, in person Anthropometric measurement, researcher-administered
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: none
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: 7 years
Strength of associations reported
Association between breast cancer recurrence and BMI, BMI 27.8-54.8 vs 21.9-24.5, HR=1.72(1.27-2.34) trend p<0.001
Association between breast cancer mortality and BMI, BMI 27.8-54.8 vs 21.9-24.5, HR=1.78(1.25-2.53) trend p<0.001
Results Comments
Insulin and BMI were strongly correlated through Spearman's correlation analysis even though insulin was significantly associated with overall survival after adjustment for BMI. These results show that the effects of insulin and BMI on breast cancer outcome are independent of one another.
Author address
Department of Medicine, Division of Clinical Epidemiology at the Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Ave., Toronto, Ontario M5G 1X5, Canada. pgoodwin@mtsinai.on.ca