riday August 3 5:51 PM ET
NEW YORK (Reuters Health) - The sex hormone estrogen may be responsible for putting women at a higher risk for lung cancer, possibly by increasing the effects of known cancer-causing agents, according to a new article published in a medical journal.
``Women may have this extra risk factor,'' Dr. Jill Siegfried, co-director of the Lung Cancer Program at the University of Pittsburgh Cancer Institute in Pittsburgh, Pennsylvania, told Reuters Health. ``That's only going to make smoking that much more harmful in women.'' Researchers have some evidence that women may be even more vulnerable to developing lung cancer than men. For example, on average, women who are diagnosed with lung cancer have smoked less than men diagnosed with the disease, and women who do not smoke are diagnosed with lung cancer more than twice as often as men who do not smoke.
In particular, the evidence that estrogen plays some role in lung cancer is strong, Siegfried said.
``When we grow lung tumors in mice and give the mice estrogen, the tumors grow much faster,'' she said. Similarly, women who have less exposure to estrogen throughout their lifetime, such as those who undergo early menopause, have been found to have a lowered risk of lung cancer, while women who take estrogen replacement therapy have an elevated risk.
One possible explanation for these findings, Siegfried said, is that estrogen strengthens the effects of carcinogens such as environmental tobacco smoke, cooking fumes and radon.
``Estrogen can cause increased growth of lung cells, which might drive the carcinogenic process,'' Siegfried said. ``With a weak carcinogen, the effect might be magnified.''
However, she said, there are other possible reasons for women's greater vulnerability to lung cancer, including less of an ability to correct genetic mistakes in cells or a greater risk of lung diseases such as emphysema.
The report was published in the August issue of the British journal The Lancet Oncology. Siegfried's work is funded by the National Cancer Institute.
The US Surgeon General dubbed lung cancer in women, which causes more deaths than breast cancer, ``a full-blown epidemic'' in a 2001 report ``Women and Smoking.'' Lung cancer is now the leading cause of cancer deaths among US women, with approximately 60,000 deaths per year.SOURCE: The Lancet Oncology