A group of heavy Marlboro smokers filed a lawsuit in federal court Thursday, asking Philip Morris USA to pay for screenings that may detect the early stages of lung cancer.

The class-action lawsuit, which was filed on behalf of current and former Marlboro smokers over 50 years old who smoked a pack or more a day for 20 years, demands the tobacco company pay for an annual low-dose CT scan of the chest.

CT scans are special X-rays and a low-dose scan is used to minimize the risk that the procedure itself could cause cancer.

The plaintiffs, from New York, are not seeking compensatory or punitive damages, according to the lawsuit.

A spokesman for Altria Group Inc. (MO), the parent of Philip Morris, said his company had not yet seen the lawsuit, but said juries in two other cases in which smokers sought payment for "medical monitoring," ruled in favor of the tobacco company.

Philip Morris should pay for the scans because its "misconduct in manufacturing and selling Marlboro cigarettes, was and remains egregious and renders it liable," according to the lawsuit filed in U.S. District Court in Brooklyn.

Jerome Block, a New York attorney representing the plaintiffs, estimated the class size in the "tens of thousands" and said annual scans cost about $500 each.

"With early detection, the lung cancer can be found while it is still curable," Block said. "Stage-one lung cancers are very curable but most lung cancer is diagnosed too late for treatment."

Lung cancer is the No. 1 cancer killer, resulting in 30 percent of all cancer deaths and killing more people annually than breast, prostate, colon, liver and kidney cancers combined, according to the non-profit Lung Cancer Alliance.

Studies have found that a low-dose CT scan can help in the early detection of cancer but there is some debate.

"There is an ongoing discussion of whether this should be used across the board as an effective way of screening for cancer," said Dr. Norman Edelman, chief medical officer for the American Lung Association.

"It's controversial because you pick up more lumps that aren't tumors so the big issue is whether you are doing more harm than good by operating on those tumors," he said.