CT Screening Increases Lung Cancer Detection, but Mortality Is Unchanged

March 6, 2007

NEW YORK -- CT screening dramatically increased the number of small lung cancers detected and the rate of curative surgery, but mortality didn't change, according to researchers here.

NEW YORK, March 6 -- CT-scan screening dramatically increases the number of small lung cancers detected and the rate of curative surgery, according to researchers here.

But in a combined analysis of three single-institution studies, screening had no effect on the lung cancer mortality rate or on the rate of late-stage lung cancer diagnosis, found Peter Bach, M.D., of Memorial Sloan-Kettering Cancer Center.

The finding implies that the additional small cancers detected by CT screening are unlikely to grow rapidly enough to significantly affect lung cancer mortality overall, Dr. Bach and colleagues reported in the March 7 issue of the Journal of the American Medical Association.

"Early detection and additional treatment did not save lives but did subject patients to invasive and possibly unnecessary treatments," Dr. Bach said.

"Ours is the first study to ask whether detecting very small growths in the lung by CT is the same as intercepting cancers before they spread and become incurable," Dr. Bach said. "We found an answer and it was, 'no'."

The finding appears to contradict the recently published International Early Action Lung Cancer Program (I-ELCAP) study, which showed that CT screening prolonged survival. (Spiral CT Screening for Lung Cancer Detects Early Curable Disease)

But Dr. Bach and colleagues said the contradiction may be only apparent, because prolonged survival of lung-cancer patients is necessary but not sufficient for there to be an effect on overall mortality.

To lower mortality, the authors argued, "computed tomography screening must also intercept at an early stage those cancers that will later progress to cause clinical disease and death, and in our study, CT screening did not intercept these cancers."

In fact, they said, few of the patients who eventually died of lung cancer in the three cohorts were among those diagnosed by CT screening and subsequently treated for early lung cancer.

The three cohorts -- at the Instituto Tumori in Milan, Italy, the Mayo Clinic in Rochester, Minn., and the Moffitt Cancer Center in Tampa, Fla. -- included a total of 3,246 asymptomatic men and women (median age of 60) who had smoked or still smoked for an average of 39 years.

The volunteers were given annual CT scans and Dr. Bach and colleagues compared their lung cancer outcomes (from national vital statistics databases) with a validated model of lung cancer.

The analysis found that after a median follow-up of 3.9 years :

  • 144 volunteers were diagnosed with lung cancer, compared with 44.5 expected cases. The relative risk was 3.2, with a 95% confidence interval from 2.7 to 3.8, which was significant at P