More Evidence Backs Routine CT Scans for Early Lung Cancer Detection
Yearly tests picked up malignant tumors sooner than X-rays, study found
A public comment period on the task force's draft recommendation ended on Aug. 26. The health care community now awaits the panel's final rule.
The U.S. study follows up on earlier findings that showed that three years of low-dose CT scans reduced lung cancer deaths by about 20 percent. The trial involved more than 53,000 people who were assigned either CT scans or chest X-rays for three years.
The new study provides more detail on how the follow-up annual scans improve the effectiveness of screening, Chiles said.
"You have to show not only an increase in the number of patients with early stage, you also have to show a decrease in the number of advanced-stage lung cancer," Chiles said. "That way, we know the true benefit comes with the screenings that come in the following year, and the year after that. Cancer was not detectable the year earlier."
Early stage lung cancer accounted for about half of the cancers detected by CT scans in the first and second follow-up years. Only 24 percent of the cancers detected by chest X-rays were early stage.
At the same time, CT scans detected half as many cancers that had been allowed to progress to the last stage: 15 percent of all cancers detected, compared with 30 percent of all the cancers detected by X-rays.
"We saw a significant decrease in the number of late-stage lung cancers," Chiles said. "We feel we showed a shift to early stage treatable lung cancer in the low-dose CT group."
The Canadian researchers took a similar multiyear tack. They used their checklist to assess the potential hazard of lung nodules detected during the first CT scans, and then used two years of follow-up lung screenings to see whether their model worked.
A total of more than 12,000 lung cancer nodules observed on CTs of nearly 3,000 current and former smokers were examined.
The checklist runs counter to current standards, which mainly rely on the size of a nodule to determine whether more tests should be run.
But the team found that in one of five study participants, the largest nodule in their lungs did not prove malignant. Other dynamics like the shape of the mass, its location in the lung, and the individual person's risk factor must be accounted for to properly assess the hazard posed.
For example, nodules located in the upper lobes of the lungs increased the likelihood of cancer, the report says. However, more nodules found in a CT scan actually decreases cancer risk.
The new model is much better at predicting cancer than previous checklists, said Dr. Christine Berg, co-principal investigator of the National Lung Screening Trial for the U.S. National Cancer Institute.