Noninvasive positron emission tomography (PET) imaging may allow earlier prediction of a patient's response to chemotherapy for ovarian cancer, according to research reported at the Society of Nuclear Medicine's 52nd Annual Meeting June 18–22 in Toronto.
"PET might be a promising tool for early prediction of response to chemotherapy and to individualize treatment for patients," noted Norbert Avril, chief of the division of nuclear medicine at the University of Pittsburgh Medical Center, Pittsburgh, Pa. "The development of new methods that allow earlier monitoring of response to treatment is highly relevant in the current clinical setting," said Avril, who performed the study at the Technical University of Munich. "It is important to identify response to therapy as early as possible so that ineffective therapies can be discontinued. Patients who are not responding to a given chemotherapy are not only suffering from unnecessary side effects but might be offered potentially more effective treatments," explained the senior author of "Sequential FDG-PET for Prediction of Survival Following Neoadjuvant Chemotherapy in Advanced Ovarian Cancer."
FDG PET can identify primary ovarian cancer as well as tumor spread in the pelvis and abdominal cavity. PET uses the radiolabeled glucose analogue F-18-fluorodeoxyglucose (FDG) to visualize the increased metabolic activity of cancer cells. FDG is taken up by cancer cells together with the glucose, and the amount of FDG taken up is measured with PET imaging. The researchers found that there is little or no decrease in the metabolic activity of non-responding tumors, but there is a significant decrease in glucose metabolism in responding tumors already after the first cycle of chemotherapy.
"Computed tomography (CT) and magnetic resonance imaging (MRI) are typically used to evaluate response to chemotherapy," explained Avril. "The decrease in tumor size is the most important criterion to assess if chemotherapy was successful. Both imaging modalities, CT and MRI, have certain limitations in imaging tumor sites in the abdomen and pelvis. More important, several cycles of chemotherapy are generally necessary before the tumor size changes and physicians know if the treatment was successful," he said. These results suggest that sequential FDG PET could be used to predict response to neoadjuvant chemotherapy in advanced stage ovarian cancer as early as after the first cycle of chemotherapy. This would be significantly better than with current CT or MRI, said Avril. Although the research team's findings were "exciting," Avril added, "Our results need to be confirmed by larger prospective (multicenter) trials."
During the past 10 years, FDG-PET imaging has gained increasing acceptance for staging of various types of cancer, said Avril. "FDG PET holds promise to be more accurate than current CT and MR imaging for the assessment of response to chemotherapy," he explained, saying that the use of serial FDG-PET at baseline and after one cycle of chemotherapy to predict if patients would benefit from continued chemotherapy could significantly increase the use of PET imaging.
"This research highlights an important trend in PET," agreed Lale Kostakoglu, M.D., an associate professor at Cornell University's Weill Medical School who is also on staff in the department of radiology, division of nuclear medicine, at New York Presbyterian Hospital. "This team of researchers from Munich used PET not just for diagnosis or staging of ovarian cancer, but for prognosis," she added. "Sequential FDG-PET for Prediction of Survival Following Neoadjuvant Chemotherapy in Advanced Ovarian Cancer" was written by Stefanie Sassen, department of nuclear medicine and pathology, Technische Universitaet Muenchen, Munich, Germany; Walther Kuhn, gynecology, Technische Universitaet Muenchen, Munich, Germany, and gynecology, University of Bonn, Bonn, Germany; Joerg Naehrig, pathology, Technische Universitaet Muenchen, Munich, Germany; Barbara Schmalfeldt, gynecology, Technische Universitaet Muenchen, Munich, Germany; Wolfgang A. Weber, nuclear medicine, Technische Universitaet Muenchen, Munich, Germany, and medical and molecular pharmacology, University of California, Los Angeles, Calif.; Markus Schwaiger, nuclear medicine, Technische Universitaet Muenchen, Munich, Germany; and Norbert Avril, nuclear medicine, Technische Universitaet Muenchen, Munich, Germany, and division of nuclear medicine, University of Pittsburgh Medical Center, Pittsburgh, Pa. The team's work was done at the Technical University in Munich and funded by internal sources.