Whole-body PET/CT superior to whole-body MRI for tumor staging

In a comparative study, whole-body dual-modality imaging using positron emission tomography (PET) and computed tomography (CT) proved more accurate than whole-body magnetic resonance imaging (MRI) for staging a variety of malignancies.

Dr. Gerald Antoch from University Hospital Essen, Germany, said this study also demonstrates the feasibility and diagnostic accuracy of whole-body tumor staging in a single session. “In most centers, tumor staging is still performed by use of more than one imaging procedure, thus increasing the time between tumor diagnosis and complete tumor staging as well as the overall cost for tumor staging,” he told Reuters Health. In the prospective, blinded study, 98 adults with various cancers underwent whole-body imaging with PET/CT and then MRI for tumor staging. PET/CT and MRI correctly determined the overall TNM (primary tumor, regional lymph nodes, and distant metastasis) stage in 77% and 54% of patients, respectively. In separate studies of T-stage (with pathological verification) in 46 patients, PET/CT was accurate in 37 patients (80%) and MRI was accurate in 24 patients (52%). In all 98 patients, N-stage was correctly determined in 91 (93%) with PET/CT and in 77 (79%) with MRI. Both imaging modalities detected distant metastases equally well. It is noteworthy, Dr. Antoch said, that the treatment regimen was altered in substantially more patients when staging was based on PET/CT. PET/CT had a direct impact on management in 12 patients while MRI results changed the treatment plan of 2 patients. Based on this comparative trial, PET/CT “can be recommended as a first-line tool for whole-body tumor staging of different oncological diseases,” the authors write in the December 24/31 double issue of The Journal of the American Medical Association. “In the future,” Dr. Antoch said, “the development and implementation of new, more specific radioactive tracers for PET and PET/CT may further increase diagnostic accuracy when staging malignant diseases.” Two editorialists writing in JAMA wonder whether some of the superiority of PET/CT over MRI might be due to the inclusion of a large number of patients with lung tumors. Drs. Lennart Blomqvist and Michael R. Torkzad of the Karolinska Institute in Sweden also note that “one of the most important, if not the only, indication for whole-body imaging is the search for metastases.” On this front, “somewhat surprisingly,” PET/CT and MRI were comparable. The editorialists conclude that “while these results are intriguing, additional studies are needed to establish the role of whole-body imaging for tumor staging in oncology practice.” (Source: JAMA 2003;290:3199-3206,3248-3249: Reuters Health: Megan Rauscher: December 23, 2003: Oncolink)