Smokers are less likely to be alive and cancer-free three years after having surgery for colon cancer than people who have never smoked, according to a new study.
Out of about 2,000 people who had part of their colon surgically removed, researchers found 74 percent of those who had never smoked were cancer-free three years later, compared to 70 percent of smokers.
Amanda Phipps, the study's lead author from the Fred Hutchinson Cancer Research Center in Seattle, said the results provide another reason why people should quit smoking.
"It's nice when you have findings that portray a consistent public health message," said Phipps.
According to the American Cancer Society (ACS), certain ingredients in cigarettes can dissolve into a person's saliva and cause colon and other cancers.
The ACS estimates about 102,500 Americans will be diagnosed with colon and rectal cancers in 2013, and over 40,000 will die from those diseases.
Phipps and her colleagues previously found smokers with colon cancer were more likely to die than non-smokers from any cause and specifically from their cancers. But the researchers wanted to take a closer look at what smoking meant for colon cancer recurrence.
For the new study, they analyzed surveys that were given to about 2,000 people between 2004 and 2005 after they had colon cancer surgery but before they received additional treatment.
Overall, 931 people said they had never smoked and 1,028 said they had smoked at least 100 cigarettes during their lifetime.
Phipps and her colleagues found people who reported smoking were 23 percent more likely to die or have their cancer return within three years, based on ongoing surveillance of those patients.
The difference was even more pronounced for the 140 people who said they were smoking at the time they were diagnosed with colon cancer. They were 47 percent more likely to have a cancer recurrence or to die than people who had never smoked.
"There is a difference. Certainly we see those current smokers have a poorer prognosis," Phipps told Reuters Health.
The researchers found smoking was tied to worse outcomes in people with tumors with certain genetic patterns but not others. Tumors that were positive for so-called KRAS mutations, for example, came with a significantly worse prognosis among smokers than non-smokers.
Overall, the researchers wrote in the Journal of Clinical Oncology that their findings show "the effects of smoking may extend beyond an adverse impact on colon cancer risk to also adversely impact outcomes after diagnosis."
The results only looked at outcomes over a short period of time, Phipps noted.
She added that for people who continue to smoke, the health risks - such as for heart disease and other cancers -- will continue to accrue as times goes on.
"I would say as we get further and further away from a colon cancer diagnosis, the impact from smoking is going to get greater," she said.