PET/CT shows chemo effectiveness after first dose

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Using a PET/CT scanner, researchers found that the response of patients receiving chemotherapy treatment could be determined about a week after the first dose of chemotherapy drugs, according to a study published in the April 15 issue of Clinical Cancer Research.

Investigators from University of California, Los Angeles' Jonsson Comprehensive Cancer Center monitored 50 patients undergoing treatment for high-grade soft tissue sarcomas. The participants were receiving neoadjuvant chemotherapy treatments to shrink their tumors prior to surgery.

"The question was, how early could we pick up a response? We wanted to see if we could determine response after a single administration of chemotherapy," said the study's senior author Fritz Eilber, MD, an assistant professor of surgical oncology and director of the Sarcoma Program at Jonsson. "There's no point in giving a patient a treatment that isn't working. These treatments make patients very sick and have long-term serious side effects."

For the study, Eilber and colleagues used FDG PET to monitor the tumor's metabolic function, or how much sugar was being consumed by the cancer cells. 

To identify an effective response to treatment, researchers needed to see a 35 percent decrease in the tumor's metabolic activity. Of the 50 patients, 28 did not respond and the researchers knew within a week of their initial treatment, which allows the treatment course to be discontinued or changed to another more effective treatment, getting the patient to surgery more quickly, the authors wrote.

"The significance of this study was that it identified people -- more than half of those in the study -- who were not going to benefit from the treatment early in the course of their therapy," Eilber said. "This information significantly helps guide patient care. Although this study was performed in patients scheduled for surgery, I think these findings will have an even greater impact on patients with inoperable tumors or metastatic disease as you get a much quicker evaluation of treatment effectiveness and can make decisions that will hugely impact quality of life."

Eilber said he was surprised how soon response to therapy could be determined. "We had an idea that patients either respond or do not respond to treatment, but we weren't sure how early you could see that," he said. "I really was not sure we would be able to see effectiveness this early."

Eilber and colleagues will continue to follow the patients and a clinical trial currently is underway based on the results of this study. Eilber believes it will help personalize treatment for each patient and may one day become the standard of care.