November 18 (HealthDay News) -- Canadian scientists may have discovered a genetic trait that could provide an early indication of which former smokers will develop lung cancer.

The research, reported Tuesday at the American Association for Cancer Research conference in Washington, D.C., is still in the preliminary stages.

Still, "the benefit would hopefully be more targeted treatment," said study author Emily A. Vucic, a graduate student at British Columbia Cancer Research Centre in Vancouver.

While smoking rates continue to shrink, lung cancer remains the second most common cancer in the United States for both genders. According to the American Cancer Society, it trails only breast cancer (in women) and prostate cancer (in men).

The society estimates that 161,840 Americans will die this year from lung cancer. An estimated 85 percent to 90 percent of cases across the world are caused by smoking.

In the new study, Vucic and colleagues examined the DNA of eight former smokers who had undergone lung cancer surgery and eight former smokers who had not. The DNA was collected from tissue in their airways.

The researchers looked for signs of damage to the DNA in the cells that make up the tissue. If damage exists, genes in the cell may not be able to prevent the cells from multiplying and turning into cancer cells, Vucic said.

The DNA is "definitely affected by cigarette smoke," she said.

The study found that there were more signs of damage in the former smokers who developed lung cancer. It's possible that a simple mouth swab could provide DNA for testing and give doctors an idea of the lung-cancer prospects for patients, Vucic said.

The scientists now plan to enroll 100 people in a follow-up trial, Vucic said.

In another study to be released at the meeting, researchers reported that cruciferous vegetables can help current and former smokers avoid lung cancer. The vegetables include broccoli, cauliflower, cabbage, Brussels sprouts, collard greens and some Chinese vegetables.

Those who ate the most raw cruciferous vegetables (at least 4.5 servings per month) had a lower risk of lung cancer than those who ate less than 2.5 servings a month. Comparing the two groups after controlling for other factors, the rates were 20 percent to 55 percent lower in the first group, depending on the types of vegetable eaten and the duration and intensity of smoking, said Dr. Li Tang, a researcher at the Roswell Park Cancer Institute in Buffalo.

Other research has linked the vegetables to lower rates of bladder cancer, Tang said. The vegetables appear to produce reactions in the body that help prevent cancer.

"Quitting smoking is the best thing to do to reduce risk, but there are things, like increasing intake of vegetables, that may also reduce your risk," Tang said.

SOURCES: Emily A. Vucic, graduate student, British Columbia Cancer Research Centre, Vancouver, B.C.; Li Tang, M.D., Ph.D., researchers, Roswell Park Cancer Institute, Buffalo, N.Y.; Nov. 18, 2008, presentation, American Association for Research's Frontiers in Cancer Prevention Research conference, Washington, D.C.