Campus Connection

Waiting to exhale
(continued)

This was not always the case; before the advent of fil- tered nicotine sticks, squamous cell carcinoma was the most common lung cancer. Then in the 1970s, the National Cancer Institute funded a number of studies aimed at developing safer cigarettes. Eventually, scientists recommended filtered cigarettes as a way of lessening the risk of cancer by reducing intake of tar.

It did nothing to make lung cancer rates decline, says Witschi. Instead, smokers developed a different but equally dangerous form of lung cancer.

Why? "Cigarette smoking is an expression of nicotine addiction, and while filters take out most of the tar, they also take out much of the nicotine," he says. "So smokers had to inhale more deeply and smoke more cigarettes to get their nicotine fix. In the process they got more volatile carcinogens and nitrosamines into their lungs."

Not that it makes much difference to the smokers who develop lung cancer. Regardless of what tissue it originates in, lung cancer is tough to treat, partly because it's often diagnosed late and partly because it's an aggressive disease. About 150,000 Americans a year die of lung cancer, 90 percent of them current or former smokers. Average survival time after diagnosis is less than a year.

Witschi's work began as a study of how secondhand smoke (which researchers prefer to call environmental tobacco smoke) affects lung development. He started out by trying to produce lung cancer in mice in a laboratory setting by exposing them to a mixture of mainstream smoke - smoke exhaled by the smoker - and sidestream smoke that drifts off the end of a cigarette.