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Lung Cancer Health Center

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More Evidence Backs Routine CT Scans for Early Lung Cancer Detection

Yearly tests picked up malignant tumors sooner than X-rays, study found


The U.S. Preventive Services Task Force -- an independent volunteer panel of national health experts -- has recommended regular low-dose screenings for current and former smokers aged 55 to 80 with at least a 30 "pack-year" history of smoking who have had a cigarette sometime within the last 15 years.

Pack years are determined by multiplying the number of packs smoked daily by the number of years a person has smoked. For example, a person who has smoked two packs a day for 15 years has 30 pack years, as has a person who has smoked a pack a day for 30 years.

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."

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