Scientists Do Not Advocate Smoking, as Risks Outweigh Advantages. Only one out of every 250 women has one of the inherited mutated genes, BRCA1 or BRCA2, whose normal function is not yet fully understood. In the United States and in some European countries, as many women die from smoking-induced lung cancer as from breast cancer. Scientists believe that smoking influences the metabolism of estrogen, a female sex hormone assumed to be involved in the development of breast cancer. The reduction in breast cancer risk by smokers with the mutated gene may be associated with reduced levels of circulating estrogens.
Breast cancer is the most frequent cancer striking women worldwide.
In Western countries, one woman in nine is likely to suffer from the disease. The mutated gene leads to just two percent of all breast cancer cases, however. A variety of risk factors has been identified as influencing the development of breast cancer, including dietary habits, reproductive lifestyle and radiation. The study, however, can lead to a better understanding of how some cancers are formed, and how they can be prevented. Previous studies have found that smokers are also at a decreased risk of endometrial cancer, another hormone-dependent cancer.