Shared risk
In the US study looking at almost 150 000 women from the Nurses' Health Study; it was found that breast cancer rates increased with higher levels of smoking among younger age groups. The study appeared in the journal Archives of Internal Medicine.
The team led by Dr Fei Xue, from Harvard Medical School, Boston added that smoking after the menopause slightly reduced the risk of breast cancer, possibly because it helped lower levels of the hormone estrogen. Previous studies have shown mixed results and some even suggest that smoking might protect against the disease. No significant association was seen between passive smoking, or light and moderate smoking, and breast cancer in this study. However, women who smoked heavily and took up the habit early in life were at increased risk. For those who started using tobacco before giving birth for the first time, smoking the equivalent of 20 cigarettes a day for 20 years raised the risk of breast cancer by 18%.
In another study published in the 24 January online edition of the journal Cancer, a drug commonly used in the treatment of breast cancer could also reduce the risk of dying from lung cancer.
The researchers found that breast cancer drug tamoxifen lowered the risk of dying from lung cancer among women who already had breast cancer. However, the results are too preliminary to warrant giving tamoxifen to lung cancer patients.
Dr. Apar Kishor Ganti, assistant professor of oncology-haematology at the University of Nebraska Medical Centre in Omaha said, "There aren't a whole lot of clinical implications, but it does provide more evidence to our accumulating knowledge that female sex hormones are involved in some way, shape or form in lung cancer progression... Whether or not it's a cause is a little sketchy." Ganti was not involved with the study.
Earlier studies have shown that lung cancers, like breast and gynaecological cancers, express hormone receptors. In the current study, Dr. Elisabetta Rapiti, from the Geneva Cancer Registry, and colleagues reviewed records of 6,655 women diagnosed with breast cancer in Switzerland between 1980 and 2003. Just under half (46%) received anti-estrogen therapy which, during that time period, was most likely tamoxifen. Women taking anti-estrogen therapy had an 87% decreased risk of death from lung cancer, compared to women who were not taking this type of therapy noted researchers.
Ganti however points out that only 40 women actually developed lung cancer, so it was a very small study group. The estrogen receptors implicated in lung cancer "don't seem to discriminate between men and women," Ganti said, indicating that anti-estrogens might have the same effect in men, although it is too early to state this definitively. Jing Peng, a post-doctoral associate in the Cancer Prevention Program at Fox Chase Cancer Centre in Philadelphia added that other cancers than breast and gynaecological cancers, such as ovarian cancers, lung cancer has been the most extensively studied with regard to its interplay with estrogen. There is limited evidence that estrogen may play a role in head-and-neck cancers as well. She added that further studies can clarify the actual relation of estrogen with all these cancers.
