Lung CT screening saves at-risk lives

October 27, 2006

Eighty percent of people whose lung cancer is caught early with CT screening can expect to live for at least another decade, according to a study in yesterday’s New England Journal of Medicine.

Eighty percent of people whose lung cancer is caught early with CT screening can expect to live for at least another decade, according to a study in yesterday's New England Journal of Medicine.

The data are the latest from the International Early Lung Cancer Action Program (I-ELCAP) led by Dr. Claudia I. Henschke, a professor of radiology and cardiothoracic surgery at Weill Medical College of Cornell University.

Typically, I-ELCAP data draw fire because the study is a systematic case-control observational study, not the gold standard randomized trial.

"Nevertheless, before the I-ELCAP study, we lacked documentation of the results of a detection test combined with planned management and long-term follow-up," said Dr. Michael Unger, a pulmonologist at Fox Chase Cancer Center in Philadelphia, in an accompanying editorial.

Henschke and colleagues referenced several studies, albeit small ones, with similar 10-year survival rates among patients with pathological stage I cancer. Additionally, they cited the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) registry, the largest U.S. cancer registry, which reported an eight-year survival rate of 75% among patients with pathological stage I cancer with nodules less than 15 mm who had undergone resection.

"Although the lung cancers in these [studies] were not detected on CT screening, most were presumably incidentally detected on imaging performed for other reasons in people who had no symptoms of lung cancer," the authors said.

For the current study, participants were considered at risk of lung cancer because they had a history of cigarette smoking, were exposed to environmental risks such as asbestos, beryllium, or uranium, or were exposed to secondhand smoke though never smokers themselves.

Baseline screening of more than 31,000 asymptomatic persons using low-dose CT resulted in 405 diagnoses of lung cancer. Repeat screenings from seven to 18 months after baseline for more than 27,000 participants resulted in 74 cases of cancer. Another five participants received interim diagnoses of lung cancer.

The estimated 10-year survival rate for all 484 participants with cancer, regardless of tumor stage and treatment, was 80%. As of May 2006, 75 of those 484 had died of lung cancer, including two who died within four weeks after surgery (yielding an operative mortality rate of 0.5%).

Of the 484 cases of lung cancer, 412 (85%) were classified as stage I based on imaging findings. The estimated 10-year survival rate in this subgroup rose to 88%.

Among the 302 participants with clinical stage I cancer who underwent surgical resection within one month after diagnosis, the survival rate went up to 92%. The eight participants with clinical stage I cancer who did not receive treatment died within five years after diagnosis.

Median tumor diameter for stage I cancers was 13 mm at baseline and 9 mm on annual CT.

The authors pointed out that approximately 95% of people currently diagnosed with lung cancer die from it, whereas the ELCAP protocol could save 80% of those diagnosed with stage I cancer.

But do these results justify screening at-risk people? Investigators say yes. They compare their detection rates with those from mammography screening in subjects 40 years of age and older:

  • lung: 1.3% on baseline screening and 0.3% on annual screening

  • breast: 0.6% to 1% on baseline screening and 0.2% to 0.4% on annual screening

Using the original ELCAP data with participants more at risk (only smokers and former smokers) and at least 60 years of age, however, detection increases to 2.7% on baseline and 0.6% on repeat screen.

Researchers pegged the cost of low-dose CT at below $200 and noted that surgery for stage I lung cancer is less than half the cost of late-stage treatment. They concluded that this type of screening is cost-effective.

In the accompanying editorial, Unger praised the I-ELCAP protocols as being adaptable because academic institutions as well as community hospitals took part in the study. He also raised some questions, however, about possible lead time and overdiagnosis bias without researchers' consideration of tumor biology.

Many in the field are awaiting the results of several ongoing randomized controlled screening trials, including one from the National Institutes of Health and another at the Mayo Clinic. They say these results will definitively answer whether early screening with CT saves lives.

In the meantime, ELCAP has stirred up interest in the general public.

"The study reported by Henschke et al ... is a provocative, welcome salvo in the long struggle to reduce the tremendous burden of lung cancer on society," Unger said.

For more information from the Diagnostic Imaging archives:

Ablation, radiotherapy boost lung cancer patients' survival

Imaging improves outlook for lung cancer patients

Celebrity death increases awareness of lung cancer

Staging criteria for lung cancer face update