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Open Access Research article

Predictors of competing mortality to invasive breast cancer incidence in the Canadian National Breast Screening study

Sharareh Taghipour12*, Dragan Banjevic2, Joanne Fernandes3, Anthony B Miller3, Neil Montgomery2, Andrew K S Jardine2 and Bart J Harvey3

Author affiliations

1 Ryerson University, Toronto, ON, M5B 2 K3, Canada

2 University of Toronto, 5 King's College Road, Toronto, ON, M5S 3 G8, Canada

3 Dalla Lana School of Public Health, Health Sciences Building, Room 688, 155 College Street, Toronto, ON, M5T 3 M7, Canada

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Citation and License

BMC Cancer 2012, 12:299  doi:10.1186/1471-2407-12-299

Published: 19 July 2012

Abstract

Background

Evaluating the cost-effectiveness of breast cancer screening requires estimates of the absolute risk of breast cancer, which is modified by various risk factors. Breast cancer incidence, and thus mortality, is altered by the occurrence of competing events. More accurate estimates of competing risks should improve the estimation of absolute risk of breast cancer and benefit from breast cancer screening, leading to more effective preventive, diagnostic, and treatment policies. We have previously described the effect of breast cancer risk factors on breast cancer incidence in the presence of competing risks. In this study, we investigate the association of the same risk factors with mortality as a competing event with breast cancer incidence.

Methods

We use data from the Canadian National Breast Screening Study, consisting of two randomized controlled trials, which included data on 39 risk factors for breast cancer. The participants were followed up for the incidence of breast cancer and mortality due to breast cancer and other causes. We stratified all-cause mortality into death from other types of cancer and death from non-cancer causes. We conducted separate analyses for cause-specific mortalities.

Results

We found that “age at entry” is a significant factor for all-cause mortality, and cancer-specific and non-cancer mortality. “Menstruation length” and “number of live births” are significant factors for all-cause mortality, and cancer-specific mortality. “Ever noted lumps in right/left breasts” is a factor associated with all-cause mortality, and non-cancer mortality.

Conclusions

For proper estimation of absolute risk of the main event of interest common risk factors associated with competing events should be identified and considered.

Keywords:
Invasive breast cancer; Competing mortality; Cancer-specific mortality; Non-cancer mortality; Risk factors