A new study conducted by Yujing He and team found that smoking, both actively and passively, increases women's risk of breast cancer (BC). The findings of this study were published in Frontiers in Oncology.
It has been widely debated whether smoking increases the risk of BC. Although BC was not previously believed to be a tobacco-related disease, various compounds found in tobacco have been looked at as potential BC triggers in recent years, including 4-aminobiphenyl and benzopyrene. It's unclear how smoking affects breast cancer. Therefore, this study was conducted with the goal to look at the connection between breast cancer and tobacco.

Before February 2022, a search was done in the EBSCO, PubMed, Web of Science, and Cochrane Library databases. The association between active or passive smoking and the risk of BC was investigated using the adjusted odd ratio (OR) and accompanying 95% confidence interval (CI).
The key findings of this study were:
1. This meta-analysis included a total of 77 publications with 2,326,987 participants.
2. Smoking, both actively and passively, increased the incidence of BC in women, particularly premenopausal breast cancer, but had no impact on postmenopausal BC.
3. However, active smoking had no impact on estrogen receptor-negative (ER-) breast cancer. Active smoking raised the incidence of ER+ BC.
4. The length and intensity of smoking were both favorably related with the risk of BC, but the duration of quitting smoking was adversely associated.
5. Active smoking raised the risk of breast cancer in the multiparous population but not in the nulliparous group, and it had a bigger influence on the risk of BC before the first delivery than it did after.
In conclusion, smoking-related factors (duration, intensity, years of stopping), population-related factors (status of fertility), and breast cancer subtypes all had an impact on how smoking affected breast cancer.
Reference:
He, Y., Si, Y., Li, X., Hong, J., Yu, C., & He, N. (2022). The relationship between tobacco and breast cancer incidence: A systematic review and meta-analysis of observational studies. In Frontiers in Oncology (Vol. 12). Frontiers Media SA. https://doi.org/10.3389/fonc.2022.961970