Research Cautions On False Positives For Cancer With PET Scans
Roberto Bergamaschi, MD, PhD, Chief, Colon and Rectal Surgery Division in the Department of Surgery, recently co-authored an article in the journal Tech ColoProctol warning about the possibility of false positive findings for cancer detection when using PET scans.
“Positron emission tomography–computed tomography (PET-CT) scans with [18F]-fluorodeoxyglucose (FDG) and PET–magnetic resonance imaging (MRI) have become standard practice in staging and restaging of colorectal cancer patients by providing important information about the primary cancer as well as metastases,” the authors wrote. “The PET portion of this imaging modality relies on the accumulation of radioactive glucose analog, FDG. In cancer cells, there is an overproduction of glucose transporters and, as a result, increased FDG uptake. However, not all PET-positive lesions are cancer, and in many instances, PET findings can be false positive."
“A few points need to be considered before understanding FDG,” the article states. “First, not all cancer cells use the same amount of glucose: some use more and some use less. Cancer cells with a faster metabolic rate such as colorectal adenocarcinoma are very FDG avid, whereas others such as mucinous cancers consume less glucose and therefore are less FDG avid. Inflammatory cells also have increased metabolic rates and, as a result, are FDG avid….”
There are many false-positive causes of FDG uptake,” the authors conclude. “The pattern of FDG uptake is easily identifiable as benign or malignant, especially if this is confirmed by CT or MRI findings. However, there are still a considerable number of challenging PET findings that may lead to false interpretation with subsequent inappropriate treatment decisions. When seeing a new focus of FDG uptake, before informing the patient that the lesion is cancer, the surgeon and oncologist must determine whether this is truly a cancer or a possible false-positive finding.”
Dr. Roberto Bergamaschi also leads the Colorectal Cancer Management Team at Stony Brook Cancer Center.