It’s the leading cause of cancer death in the United States, killing more people each year than breast, prostate, colon, liver, kidney and melanoma cancers combined.It’s typically discovered too late to be treated successfully, with about 85 percent of victims dead within five years of diagnosis.

And nine out of 10 cases of the disease are tied to a single behavior — smoking.

Lung cancer killed 160,390 people in 2007, according to the Lung Cancer Alliance. That’s an average of 439 people a day.

And tobacco caused 90 percent of those deaths, according to the U.S. National Cancer Institute.

“Smoking is the most lethal legal activity in our society,” said Dr. James Mulshine, a professor of internal medicine and associate provost for research at Rush University Medical Center in Chicago.

Researchers are trying to find better ways to detect lung cancer and to find genetic warning signs, or markers, that could predict who might be at increased risk.

But doctors say anti-smoking measures have proven the only effective weapon against the disease.

“At this point, the progress in decreasing lung cancer death rates is due solely to men quitting smoking since the early 1990s,” said Dr. Michael Thun, vice president of epidemiology and surveillance research for the American Cancer Society.

The death rate for men fell from 90.6 deaths per 100,000 people in 1990 to 69.4 deaths per 100,000 in 2005, Thun said. But the death rate for women peaked in 1998 at 41 deaths per 100,000 and has remained in that range ever since, he said.

“Lung cancer rates have been falling in men since 1991, since men began to quit smoking,” Thun said. “They have leveled off in women, but are not declining. Women started smoking later than men in our society and are having more trouble quitting.”

For some time, it was thought that women might be more susceptible to tobacco-related lung cancers than men. However, recent research from the National Cancer Institute has disproved that notion.

“It looks like the effect of tobacco is the same for women as it is for men,” said Dr. Tim Byers, deputy director of the University of Colorado Cancer Center and a professor with the university’s department of preventive medicine and biometrics.

Other recent research has discovered a genetic variant tied to lung cancer risk. Doctors earlier this year found a 70 percent increased risk of the disease among carriers of a deficient gene called Alpha 1-antitrypsin.

But given that smoking is the cause of nearly all lung cancers, doctors aren’t sure that knowledge of a genetic link will prove useful in the near term. “There’s nothing that can be done about this genetic variant,” Thun said.

The most promising area of new research involves early detection of lung cancer through the use of spiral CT scans.

Currently, when lung cancer is detected, the disease has already spread outside the lung in 15 percent to 30 percent of cases, according to the National Cancer Institute. That’s because chest X-rays can only detect larger tumors of 1 centimeter or more.

But spiral CT, a technology introduced in the 1990s, can pick up tumors well under 1 centimeter.

About 50,000 current or former smokers are participating in the National Lung Screening Trial, a study that hopes to determine in the near future whether CT scans can allow early intervention that would save a person’s life.

“We all have our fingers crossed that the trial will show there is a screening procedure that will make a difference,” Byers said. “We’re probably about two to three years away from knowing the results of that trial.”

In the meantime, doctors say the best way to save lives from lung cancer is to throw more energy into measures that will prevent smoking.

Studies have shown that raising the price of cigarettes through taxation, clean air laws that prohibit smoking in public places, and counter-advertising have all helped reduce smoking rates in the United States, Thun said.

“We know those tactics work, but, for political reasons, they’re not being fully applied,” he said.

Quitting smoking also will allow people to avoid the host of other health problems that come with it, most notably cardiovascular disease.

“If you avoid smoking, you have avoided the Mount Everest of avoidable health hazards,” Thun said.

(HealthDayNews)