Jump to full article: Ontario Tobacco Research Unit (ca), 2009-04-24
Intro: Conclusions
Causality
Active Smoking
Based on the weight of evidence from epidemiologic and toxicological studies and understanding of biological mechanisms, the associations between active smoking and both pre- and postmenopausal breast cancer are consistent with causality.
Secondhand Smoke
The association between SHS and breast cancer in younger, primarily premenopausal women who have never smoked is consistent with causality. The evidence is considered insufficient to pass judgement on SHS and postmenopausal breast cancer.
Attributable Risk
It would be premature at this time to estimate the magnitude of breast cancer incidence and mortality attributable to active and SHS; this could be a topic for further research.
Research Recommendations
Further research would help to better understand and quantify the tobacco-breast cancer risks, such as: carefully designed case-control and cohort studies with comprehensive measures of lifetime exposure to tobacco smoke, as well as measures of exposure at targeted periods of suspected increased susceptibility, e.g., puberty until giving birth for the first time; quantitative meta-analyses focusing on risk related to age at smoking initiation, smoking before pregnancy, and high duration/ high pack-years smoking; further research to better understand the dynamics between active and passive risk, and further study of tobacco risk related to targeted genotypes, particularly NAT2 and to the BRCA1 and BRCA2 mutation.
Other Considerations
Tobacco smoke is one of the few modifiable risks for breast cancer and it impacts many women.
Young women in particular, should understand that available evidence suggests that the relationship between breast cancer and both active smoking and SHS is consistent with causality. Many young women are exposed to SHS, many continue to take up smoking at a young age, and the average age of first childbirth is older than in the past, which may extend the period of enhanced vulnerability.
The public health implications of these findings highlight the need for effective messaging.
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