Feb. 11 (HealthDay News) -- Positron emission tomography (PET) is more accurate and sensitive than standard scans for measuring treatment response in sarcoma patients, UCLA researchers report.

The study, reported in the Feb. 1 issue of Clinical Cancer Research and among the first to compare PET to CT scanning, found standard scans only identified 20 percent of patients who responded to treatment, while PET identified 100 percent of responders.

Currently, sarcoma patient response to treatment is evaluated after patients are scanned using CT or MRI before and after treatment. The before and after findings are compared to determine if the tumor has shrunk. If there's no change, the disease is considered stable. Tumor shrinkage of more than 30 percent is considered partial response, while tumor elimination is considered total response.

CT and MRI scans provide anatomical images of the body, while PET provides information about numerous biochemical functions in real time.

The findings could prove important for patients, according to the UCLA researchers. They noted that if CT or MRI scans fail to detect treatment response, doctors may halt therapies that are working.

"We knew from our considerable experience with neoadjuvant therapy (treatment before surgery) in sarcoma patients that measuring tumor size correlated poorly with response," study senior author Dr. Fritz Eilber, an assistant professor of surgery and director of the Sarcoma Program at UCLA's Jonsson Cancer Center, said in a prepared statement.

"We have removed many tumors that have not changed in size with treatment or have even grown, but are completely dead on pathologic analysis. Just because the tumor doesn't shrink doesn't mean the treatment didn't work," he said.

SOURCE: University of California, Los Angeles, news release, Feb. 1, 2008