Joy Pader1, Robert B Basmadjian2, Dylan E O'Sullivan3,4, Nicole E Mealey4, Yibing Ruan1, Christine Friedenreich1,2,4, Rachel Murphy5, Edwin Wang6, May Lynn Quan7, Darren R Brenner8,9,10,11. 1. Department of Cancer Epidemiology and Prevention Research, Cancer Care Alberta, Alberta Health Services, Calgary, AB, Canada. 2. Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada. 3. Department of Public Health Sciences, Queen's University, Kingston, ON, Canada. 4. Department of Oncology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada. 5. Department of Epidemiology, Biostatistics and Public Health Practice, School of Population and Public Health, University of British Columbia, Vancouver, BC, Canada. 6. Department of Biochemistry & Molecular Biology, Cumming School of Medicine, University of Calgary, Alberta, Canada. 7. Department of Surgery, Cumming School of Medicine, University of Calgary, Alberta, Canada. 8. Department of Cancer Epidemiology and Prevention Research, Cancer Care Alberta, Alberta Health Services, Calgary, AB, Canada. Darren.Brenner@ucalgary.ca. 9. Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada. Darren.Brenner@ucalgary.ca. 10. Department of Oncology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada. Darren.Brenner@ucalgary.ca. 11. Department of Oncology and Community Health Sciences, University of Calgary, Heritage Medical Research Building, 3300 Hospital Dr NW, Room 382B, Calgary, AB, T2N 4Z6, Canada. Darren.Brenner@ucalgary.ca.
Abstract
PURPOSE: Breast cancer incidence among younger women (under age 50) has increased over the past 25 years, yet little is known about the etiology among this age group. The objective of this study was to investigate relationships between modifiable and non-modifiable risk factors and early-onset breast cancer among three prospective Canadian cohorts. METHODS: A matched case-control study was conducted using data from Alberta's Tomorrow Project, BC Generations Project, and the Ontario Health Study. Participants diagnosed with breast cancer before age 50 were identified through provincial registries and matched to three control participants of similar age and follow-up. Conditional logistic regression was used to examine the association between factors and risk of early-onset breast cancer. RESULTS: In total, 609 cases and 1,827 controls were included. A body mass index ≥ 30 kg/m2 was associated with a lower risk of early-onset breast cancer (OR 0.65; 95% CI 0.47-0.90), while a waist circumference ≥ 88 cm was associated with an increased risk (OR 1.58; 95% CI 1.18-2.11). A reduced risk was found for women with ≥ 2 pregnancies (OR 0.76; 95% CI 0.59-0.99) and a first-degree family history of breast cancer was associated with an increased risk (OR 1.95; 95% CI 1.47-2.57). CONCLUSIONS: In this study, measures of adiposity, pregnancy history, and familial history of breast cancer are important risk factors for early-onset breast cancer. Evidence was insufficient to conclude if smoking, alcohol intake, fruit and vegetable consumption, and physical activity are meaningful risk factors. The results of this study could inform targeted primary and secondary prevention for early-onset breast cancer.
PURPOSE:Breast cancer incidence among younger women (under age 50) has increased over the past 25 years, yet little is known about the etiology among this age group. The objective of this study was to investigate relationships between modifiable and non-modifiable risk factors and early-onset breast cancer among three prospective Canadian cohorts. METHODS: A matched case-control study was conducted using data from Alberta's Tomorrow Project, BC Generations Project, and the Ontario Health Study. Participants diagnosed with breast cancer before age 50 were identified through provincial registries and matched to three control participants of similar age and follow-up. Conditional logistic regression was used to examine the association between factors and risk of early-onset breast cancer. RESULTS: In total, 609 cases and 1,827 controls were included. A body mass index ≥ 30 kg/m2 was associated with a lower risk of early-onset breast cancer (OR 0.65; 95% CI 0.47-0.90), while a waist circumference ≥ 88 cm was associated with an increased risk (OR 1.58; 95% CI 1.18-2.11). A reduced risk was found for women with ≥ 2 pregnancies (OR 0.76; 95% CI 0.59-0.99) and a first-degree family history of breast cancer was associated with an increased risk (OR 1.95; 95% CI 1.47-2.57). CONCLUSIONS: In this study, measures of adiposity, pregnancy history, and familial history of breast cancer are important risk factors for early-onset breast cancer. Evidence was insufficient to conclude if smoking, alcohol intake, fruit and vegetable consumption, and physical activity are meaningful risk factors. The results of this study could inform targeted primary and secondary prevention for early-onset breast cancer.
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