As many as half of smokers who are diagnosed with cancer keep smoking or relapse soon after giving up the habit—which, not surprisingly, can make matters worse. According to a new study appearing online in the journal Cancer, continuing to smoke not only increases the chances of developing cancer in another part of the body but also interferes with the effectiveness of treatment.

The study, a review of existing research on the topic, points out that the time of diagnosis is an opportune, but underused, window for smokers to give up cigarettes for good. Motivation to quit can be especially high. But doctors need to ask about smoking habits, advise patients to quit, and offer support throughout the often discouraging rounds of treatment, the study says.

"Clearly cancer patients and members of the general population smoke to handle stress," says study coauthor Damon Vidrine, a postdoctoral fellow in the University of Texas M.D. Anderson Cancer Center's behavioral science department.

Patients may also feel that "the damage is done," especially if they're diagnosed with a smoking-related form of the disease such as lung cancer, says Vidrine. But that's a dangerous misperception. Besides increasing the risk of a later cancer, continuing to smoke can cause more damage. It's known that radiation treatment doesn't work as well in smokers.

Chemotherapy also may be less effective, and the comeback from surgery is apt to be tougher than need be, too.

See our Cancer Center for more information.