Positron emission tomography superior to standard evaluation tools in measuring treatmen...( Positron Emission Tomography (PET) w...)

Positron Emission Tomography (PET) was much more sensitive and more accurate than conventional imaging methods in detecting response to treatment in sarcoma patients, according to a UCLA study that is among the first to directly compare PET to CT scanning.

The study has important implications for patients. If conventional imaging fails to detect treatment response, oncologists may discontinue therapies that in fact are working and study participants may be dismissed from clinical trials that are actually helping them. Conversely, if a patient is not responding, using PET scanning to evaluate response could help prevent them from undergoing toxic therapies that arent working.

The study, conducted by a multidiscplinary team of scientists at UCLAs Jonsson Cancer Center, appears in the Feb. 1, 2008 issue of Clinical Cancer Research. Researchers found that standard size-based evaluation methods only identified 20 percent of responders, while PET was able to identify responders 100 percent of the time.

Current practice evaluates response to treatment using RECIST, or Response Evaluation Criteria in Solid Tumors. Patients are scanned using CT or MRI before and after treatment and the scans are then compared to determine if the tumor has decreased in size. If there is no change, the disease is considered stable. A partial response is tumor shrinkage of more than 30 percent, while a total response is tumor elimination.

We knew from our considerable experience with neoadjuvant therapy (treatment before surgery) in sarcoma patients, that measuring tumor size correlated poorly with response, said Dr. Fritz Eilber, an assistant professor of surgery, director of the Sarcoma Program at UCLAs Jonsson Cancer Center and senior author of the study. 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 doesnt shrink doesnt mean the t
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