FOR THE RECORD (August 23, 1997): Quote wrong: The Associated Press, in an August 21 story, erroneously quoted Dr. Vincent Miller of Memorial Sloan-Kettering Cancer Institute in New York as saying the study was the first to explain why ex-smokers are twice as likely to develop lung cancer as those who have never smoked. Miller said several previous studies have tried to explain the phenomenon.
Doctors have told patients for years that it is never too late to quit smoking. Now a study suggests long-term smoking triggers a biological change that increases the risk of lung cancer permanently, even for ex-smokers.
Smoking the equivalent of a pack of cigarettes every day for 25 years appears to encourage both healthy and mutated lung cells to multiply, increasing the odds of developing cancer, according to a study released Thursday by the University of Pittsburgh.
“Once this switch is turned on, it appears to be permanent, which may explain in part why long-term ex-smokers who have not had a cigarette in over 25 years are still at high risk for getting lung cancer,” said Dr. Jill Siegfried, who directed the study.
The study, published in the August issue of the Journal of Respiratory and Critical Care Medicine, looked at lab-grown lung cells from 37 nonsmokers, and light and heavy smokers.
Heavy smokers were defined as those who had more than 25 “pack-years.” People who smoked two packs a day for 12-1/2 years were classified the same as those who smoked one pack a day for 25 years.
The researchers found an abnormal protein on the surface of lung cells from the heavy smokers. The protein, gastrin-releasing peptide receptor, attracts a type of hormone that stimulates cells to divide.
“The more cell growth you have, the greater the chance that one of those mutated cells will be the one that grows,” Siegfried said.
The harmful protein was not present in the light smokers, but Siegfried said a larger survey would be needed to determine when irreversible damage sets in.
Other researchers said Siegfried’s findings were significant.
Dr. Vincent Miller, a lung-cancer researcher at Memorial Sloan-Kettering Cancer Institute in New York, said the study is the first to explain why ex-smokers are twice as likely to develop lung cancer as those who have never smoked.
Many smokers mistakenly believe that when they stop, their lungs will eventually become healthy again, said Dr. Frank Cuttitta of the National Cancer Institute.
But Eric Hunsaker of Pittsburgh said the knowledge that he may be on the way to damaging his lungs permanently would not make him quit. “I don’t think any study will make you say, ‘Gee, I’m going to stop smoking,”’ Hunsaker said.