PET surveillance of patients with Ewing sarcomas of the trunk: Must the lower legs be included?

AIM:FDG-PET(/CT) is frequently used in surveillance of Ewing sarcoma (ES) patients. Since ES and PNET (primitive neuroectodermal tumours) may cause peripheral metastases some centers routinely recommend whole body PET acquisition from head to toe what may necessitate repositioning of the patient and thus extending examination time. It is not clear yet whether inclusion of lower leg adds to the diagnostic accuracy of PET scanning, especially in primary tumors of the trunk. PATIENTS, METHOD: 40 patients with ES and PNET of the trunk who were referred for surveillance after primary therapy with complete remission, were evaluated retrospectively: 27 men, 13 women; mean age at diagnosis 16.3 (3-35) years. At the time of diagnosis 28 patients had localized and 12 metastatic disease. Almost all of the patients had undergone a combined chemotherapy with surgery or/and radiotherapy. 156 follow-up PET scans of the legs of these patients were evaluated retrospectively. RESULTS:only in three (1.9%) of 156 scans a pathologic FDG accumulation was attributed to metastatic disease of the lower extremities. In these cases the observation of metastatic disease in the legs did not alter therapy, since in all three cases a multifocal disease progression was observed. CONCLUSION:scanning of the lower legs may be omitted during follow-up in patients in whom the primary tumor was located in the trunk and in whom no clinical signs pointing to metastases in the lower legs are present. This provides a sufficient diagnostic power and a shorter examination time, thus increasing patient comfort and scanner availability.