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Dr. Heidi Roberts is convinced annual CT scans could improve lung cancer survival rates.

Early screening may increase survival rates from lung cancer dramatically, but critics say the study doesn't prove finding the growths early saves lives.

Every year, 22,000 Canadians contract lung cancer, but by the time symptoms emerge, it's usually too late to treat, which is why 95 per cent of patients don't survive.

Now, researchers say early screening with CT scans helped diagnose almost 500 people with the disease, which likely would not have been detected until much later.

The study looked at 31,657 people who were at risk for lung cancer but did not show any symptoms. Of those, 302 had early lung cancer and sought immediate surgical treatment.

Talk of cure for lung cancer

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Doctors are debating if yearly CT scans are worthwhile for smokers and others at high risk. ((CBC))

In Thursday's New England Journal of Medicine, Dr. Claudia Henschke of Cornell Medical Center and her colleagues estimate 92 per cent of participants who were in the earliest stage of lung cancer and who had surgery within one month of diagnosis will survive for 10 years.

"If they are treated in a timely fashion with an appropriate treatment these people are cured from their lung cancer," said Dr. Heidi Roberts,a radiologist at Toronto's Princess Margaret Hospital who ran the Canadian part of the study.

"This is the first time we actually have a study that talks about the cure of lung cancer."

Although early screening is credited with dramatically reducing deaths from breast, colorectal and cervical cancer, critics of the study said doctors are still far from proving the same to be true for lung cancer screening.

Elsa Poitras, 60, was one of the people whose growth was discovered in the study. Poitras, who quit smoking in 1989, said she wasn't surprised when Roberts found it in its early stages. Poitras and Roberts are convinced it's time to offer screening for lung cancer across Canada.

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Elsa Poitras's lung cancer was detected early. ((CBC))

"I also wasn't upset [because] I had no symptoms," Poitras recalled. "I figured even if it is a lung cancer, at least I'm finding it early."

Lives saved?

It is easier and cheaper to treat lung cancer early on. But since the researchers did not compare participants who got scans to those who did not, the study cannot conclusively show whether screening saves more lives than doing nothing.

It's possible the screening found slow-growing tumours that may not have caused problems, critics said. After the screening, a biopsy of the lung nodule may be required, which carries a risk of a collapsed lung and other complications.

"The question of cost-effectiveness also remains unanswered," wroteDr. Michael Unger, a lung cancer specialist at theFox Chase Cancer Center in Philadelphia, in a journal commentary.

It isn't time to screen everyone at high risk, said Dr. Heather Bryant of the Alberta Cancer Board.

"We'd really like to know if finding the cancer that degree earlier really makes a difference in the patients mortality from the disease," said Bryant.

More comprehensive studies are underway in the U.S. and Europe that will provide a clearer answer, but the results are not expected for at least five years.

Smoking is the main cause of lung cancer. Exposure to second-hand smoke, asbestos, and radioactive substances are other causes.