Our study is the first to test PET-CT in a randomized setting in any cancer, Barbara Fischer of Copenhagen University Hospital, who led the study, said in the New England Journal of Medicine.

When performing a stand-alone PET, you will lack anatomical details, Fischer said via e-mail. In a PET-CT you get both metabolic and anatomic details in one examination.

The study involved 189 patients with newly diagnosed cancer, whose tumors were thought to be treatable with surgery based in part on a CT scan.

On examining further it was found that 18 of the 91 people who received conventional evaluation had inoperable cancer, compared to 38 of 98 scanned by a PET-CT unit. It lead to surgery in 73 people after conventional evaluation and in 60 people after PET-CT scan.

It was determined by doctors after surgery that 38 patients who did not get the combined scan endured surgery did not help them, compared with 21 evaluated with PET-CT.

Fisher said the results will make it unjustifiable to perform surgery on a patient with lung cancer without performing a PET-CT as part of the staging procedures, before reaching a decision on operability.

She said PET-CT scans probably improve the quality of life for non-small-cell lung cancer patients by eliminating unnecessary surgery, although it should be stressed that we have not performed a quality-of-life analysis.

Fischer said she worried that people who skipped surgery because of the scans might die sooner. But she added: We were glad to conclude that this was not the case.