New CT lung screening study continues to skirt mortality issues

March 27, 2007

Dr. Claudia I. Henschke, the dean of observational lung cancer screening studies, has reported in the April issue of Radiology that strict adherence to a CT screening regimen catches a high proportion of early disease. Last year, Henschke published a study that used a computer model to predict that 80% of people whose lung cancer is caught early with CT screening can expect to live at least another decade.

Dr. Claudia I. Henschke, the dean of observational lung cancer screening studies, has reported in the April issue of Radiology that strict adherence to a CT screening regimen catches a high proportion of early disease. Last year, Henschke published a study that used a computer model to predict that 80% of people whose lung cancer is caught early with CT screening can expect to live at least another decade.

Rather than provide the definitive word on CT lung cancer screening, however, this latest study from the archives of the Early Lung Cancer Action Project suffers from the same fatal flaw as ELCAP's previous work: It mentions nothing about the mortality rate, according to Dr. Edward F. Patz Jr., a thoracic radiologist at Duke University Medical Center.

"We want to know if CT screening will reduce the number of people who will die from this disease. Finding a lot of early-stage disease does not tell us what we need to know," Patz said.

He said that Henschke's study is reminiscent of prior chest x-ray trials, in which researchers found a lot of early-stage cancer and a greater than five-year survival rate in those treated. The difference is that these studies found no reduction in mortality between the screened and the unscreened arms.

In the latest study, ELCAP investigators at 12 medical institutions in New York State provided baseline CT screenings to 6295 people and annual repeat screenings to 6014 of them. Nearly 15% of baseline screenings and 6% of repeat screenings required further workup.

Of the 134 recommended biopsies, 125 resulted in a diagnosis of lung cancer or another malignancy, while none of the 24 biopsies performed outside of the recommendation of the regimen resulted in a diagnosis of lung cancer.

A high proportion (89% in baseline, 85% in repeat screening) had no evidence of metastases when recommended for biopsy, indicating that a regimen of annual repeat screenings allows for detection of lung cancer at its earliest, most treatable stage, according to the study.

Physicians must understand the importance of following an optimal screening regimen, said Henschke, chief of the divisions of chest imaging and health care policy and technology assessment at New York-Presbyterian Hospital/Weill Cornell Medical Center in New York City.

"This is critical, as it provides the opportunity for earlier treatment, which can be curative," she said.

Critics argue that showing an increase in the cure rate is not the same as showing a decrease in the mortality rate. A study by Bach et al in the March 7 issue of the Journal of the American Medical Association found that screening CT leads to early lung cancer diagnosis and an increase in survival but does not cut lung cancer death rates.

Bach, who used a computer model as a control group, found in the screened group more than three times as many lung cancers, resulting in 10 times the number of surgeries.

"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. We found an answer, and it was no," Bach said.

Henschke cited numerous concerns about the validity of Bach's newly developed computer model. The main problem with Bach's study is that it focused on too short a time period to assess the decrease in lung cancer deaths, which starts to be evident after the first five years of screening, she said.

Henschke's observational studies have always focused on the cure rate rather than a reduction in mortality. Many in the radiology community await the results of the National Lung Screening Trial, an eight-year $200 million randomized controlled trial under the auspices of the National Cancer Institute.

Now in its fifth year, the NLST hopes to discover whether lung cancer screening with low-dose multislice CT can reduce mortality compared with chest x-ray. The trial concluded its enrollment of 52,000 participants in February 2004.

For more information from the Diagnostic Imaging archives:

Study questions ability of CT screening to reduce lung cancer deaths

Lung CT screening saves at-risk lives

Imaging improves outlook for lung cancer patients

Staging criteria for lung cancer face update