FDG-PET imaging predicts lung cancer patients' response to chemotherapy

May 10 2007

An earlier indication of whether chemotherapy benefits non-small cell lung cancer patients, provided by positron emission tomography (PET) imaging, can guide doctors in offering them better care, according to researchers in the May Journal of Nuclear Medicine.

"Our study demonstrates that patients who respond to chemotherapy can be identified early in the course of their treatment, and these patients will generally exhibit prolonged overall survival," explained Claude Nahmias, professor of radiology and medicine at the University of Tennessee Medical Center in Knoxville. "Although we studied a relatively small number of patients, and our results should be interpreted with caution, it is clear that a repeat PET study with the radiotracer fluorodeoxyglucose (FDG) at the end of the first cycle of chemotherapy would allow the identification of those patients for whom the therapy was futile," he said. "The ability to provide an early indication of therapeutic response has the potential to improve patient care by identifying those patients who do not benefit from their current treatment," explained Nahmias. "Patients would benefit from either having chemotherapy and its associated toxic side effects stopped or going on to a different, and hopefully more adequate, therapeutic approach," added the co-author of "Time Course of Early Response to Chemotherapy in non-Small Cell Lung Cancer Patients With 18F-FDG PET/CT."

non-small cell lung cancer is the most common type of lung cancer, usually growing and spreading more slowly than small cell lung cancer. Lung cancer is the second most common cancer and the most common cause of cancer-related death in both men and women in the United States. In 2007, about 213,380 new cases of lung cancer (both small cell and non-small cell) are expected in the United States, and about 160,390 people will die of this disease. For most patients with non-small cell lung cancer, current treatments do not cure the cancer.

"With non-small cell lung cancer, since the relatively modest increase in survival must be balanced against the toxicity of the chemotherapeutic treatment, the case for monitoring therapeutic response is especially compelling," said Nahmias. "To assess the response to chemotherapy in patients with advanced non-small cell lung cancer, all of the studies published thus far have evaluated the patients at one, or at most two, time points after the initiation of chemotherapy," said Nahmias. "In our study, we evaluated 15 patients weekly, for seven weeks, as they started their chemotherapy regiment. In spite of the persuasive findings of several studies investigating PET for monitoring response to cancer therapy, until now no published reports have clearly demonstrated that PET results were used to alter treatment," he noted.

PET is a powerful molecular imaging procedure that noninvasively demonstrates the function of organs and other tissues. When PET is used to image cancer, a radiopharmaceutical (such as FDG, which includes both a sugar and a radionuclide) is injected into a patient. Cancer cells metabolize sugar at higher rates than normal cells, and the radiopharmaceutical is drawn in higher amounts to cancerous areas. PET scans show where FDG is by tracking the gamma rays given off by the radionuclide tagging the drug and producing three-dimensional images of their distribution within the body. PET scanning provides information about the body's chemistry, metabolic activity and body function.

"Our result, that PET studies one and three weeks after initiation of cancer therapy can predict success or failure of the therapy should be validated in a larger study in which patients are enrolled with the intention of applying it in patient management," said Nahmias. He added, "I am forever grateful to all the patients who came back week after week to undergo our PET scans."