Narrator: This is Science Today. Women smokers are three times more likely than men to have a common lung cancer-causing mutation known as K-ras. John Wiencke, a professor of epidemiology at the University of California, San Francisco, says in their collaborative study with Harvard University, it was also discovered men and women with this mutation had more aggressive tumors early on in the stage of their disease.

Wiencke: They're more likely to not survive following their surgery at a rate that's four times that of patients that don't have these mutations.

Narrator: More study is needed, but Wiencke says it may be estrogen that makes this mutation more common in women.

Wiencke: There had been for some time an idea that this mutation may cooperate with estrogens and promote the growth of cells, particularly cells that exist in the lung. And apparently K-ras expression increases the number of receptors on cells and this would make perhaps, a cell more responsive to estrogen and it's growth-promoting effects.

Narrator: For Science Today, I'm Larissa Branin.