Mary McCarville, MD

    Mary McCarville, MD

    A better view of tumors

    The combination of PET/CT appears to be a promising new imaging technique for use in the initial staging of pediatric sarcomas (determining how advanced the tumors are) and in following up children who have been treated for these solid tumors, according to a team of St. Jude researchers. The use of PET/CT provides information that might not otherwise be readily obtained, the researchers report. Sarcomas are malignant tumors growing from connective tissues, such as cartilage, fat, muscle or bone.

    The technique combines the ability to get anatomic information provided by CT (computed tomography) with information on the activity of living tumor tissue provided by PET scans. A report on their findings appears in the April issue of the American Journal of Roentgenology.

    PET scans take pictures of tissues and organs that have absorbed sugar-like molecules chemically tagged with an atom that releases particles called positrons, which a special camera catches and turns into images. These images include sites of abnormal growth, such as tumors. However, PET alone sometimes fails to accurately locate those tumors, according to M. Beth McCarville, MD, Radiological Sciences. And CT images alone lack metabolic information, so subtle or unexpected diseases might be overlooked, she added. 

    “Using PET/CT we identified sarcomas that had spread from their original sites to unusual locations, such as the pancreas and breast,” McCarville said. “Not only were these locations unsuspected sites of cancer, but our conventional imaging techniques for finding metastatic cancer did not identify them.” Metastatic cancers are those that have spread from the original, or primary site.

    Using PET/CT, the team was also able to find the primary site of sarcomas in several patients whose cancer had already spread widely and whose primary tumor site was otherwise not obvious on physical exam, said Sue Kaste, DO, Radiological Sciences.

    “We also found that PET/CT is valuable for monitoring the response of sarcomas to chemotherapy, radiation therapy and radiofrequency ablation [using radio waves to kill tumors],” McCarville added. “And it was helpful in determining the success of surgical removal of sarcomas.”

    The investigators found that PET/CT offered only limited help in distinguishing between benign and malignant disease in lymph nodes.

    Other St. Jude authors of this study include Najat Daw, MD, and Sheri Spunt, MD, both of Hematology-Oncology.

    Last update: May 2005