By Amy Norton
"Am I surprised by the findings? No," said Edelman, who was not involved in the study. "It's consistent with what I've seen in clinical practice. With cancer survivors, one of the problems we have is convincing them there's a point [to quitting]."
"Smoking can kill you in a lot of ways," Edelman said.
The new findings are based on nearly 3,000 U.S. adults taking part in a long-term study of cancer survivors.
"We really haven't known what happens [to smoking habits] years after a person's cancer diagnosis," said lead researcher Lee Westmaas, director of tobacco control research at the cancer society.
His team found that over 9 percent of cancer survivors were smoking almost a decade after their diagnosis.
"And they were smoking pretty heavily," Westmaas said. Current smokers averaged 15 cigarettes a day, though 40 percent smoked more than that.
What's more, people who had survived lung or bladder cancers -- two cancers closely linked to tobacco -- had the highest rates of current smoking (at 15 percent and 17 percent, respectively).
Edelman was not surprised that lung cancer survivors were among the most likely to still be smoking. "These are the hard-core smokers," he said. "Smoking cessation is not easy for them. It takes a lot of patience. Rarely do people quit on the first try."
Westmaas said it's not clear whether some of the persistent smokers had tried to quit but were unsuccessful. The "good news," he added, is that of study participants who were smoking at the time of their diagnosis, one-third did manage to quit.
According to Westmaas, the findings suggest that doctors "could do a better job" of asking cancer survivors about their smoking habits, and helping them to quit.
"For these patients," he said, "quitting smoking is the single best thing they can do to increase their survival and improve their general health in the long run."
And it's never too late to quit, according to Jamie Ostroff, director of the tobacco treatment program at Memorial Sloan Kettering Cancer Center in New York City.
"There is scientific evidence that quitting smoking improves cancer patients' prognosis," Ostroff said. That means not only better odds of surviving the cancer, but also better overall health in the long run, she noted.
So quitting is key for all cancer patients, Ostroff said -- and not just those with types of cancer that are clearly linked to smoking.
"We have safe and effective ways to quit smoking, and they should be offered to all cancer patients," Ostroff said.
Among the options are nicotine replacement therapy, medications and behavioral counseling. And most people need help. According to the cancer society, only 4 percent to 7 percent of smokers are able to quit on their own on the first try.
The reality, Edelman said, is that most people need to make several attempts before they quit for good.