Is PET useful in detecting occult nonpulmonary metastases in pediatric bone sarcomas?

UNLABELLED: Orthopaedic oncologists are increasingly utilizing positron emission tomography (PET) technology in the initial workup and staging of sarcomas and for monitoring treatment response. We evaluated the use of PET with fluorine-18-fluoro-2-deoxy D-glucose (FDG) to detect occult nonpulmonary metastases in patients < age 30 newly diagnosed with either Ewing's or osteosarcoma, and the impact of this information upon therapeutic decision making. We retrospectively reviewed prospectively collected data (1994-2004) on 55 patients age < 30 years old over a 10 year span. PET detected metastases in 12/55 (22%) of these patients, eight of whom (67%) harbored disease outside the lung; however, only 4/55 (7%) were upstaged to Stage IV specifically due to findings determined by PET alone. Three of 17 (18%) Ewing's sarcoma patients, but only one of 38 (3%) osteosarcoma patients, were upstaged by PET alone. The most important alteration in treatment decisions was the substitution of irradiation in lieu of surgery for local control in Ewing's sarcoma patients. LEVEL OF EVIDENCE: Diagnostic study, level II.

Positron Emission Tomography for pretreatment staging and posttreatment evaluation in cancer of the anal canal.

PURPOSE: In recent years, combined modality therapy (CMT) with chemotherapy and radiation has replaced surgery as the preferred treatment for cancer of the anal canal. Clinical staging with computed tomography (CT) scan alone may underestimate the extent of disease. We investigated the utility of positron emission tomography (PET) with 2-deoxy-2[F-18]fluoro-D-glucose (FDG) in the staging and determination of response to CMT. PATIENTS AND METHODS: From September 1999 to August 2002, 21 patients with cancer of the anal canal were studied prospectively. All patients underwent pretreatment PET, in addition to standard clinical evaluation that included CT scanning. Follow-up PET studies were ordered one month after completion of CMT. RESULTS: Sites of metastases not observed on CT scan were identified in five of 21 patients (24%). These sites included pelvic lymph nodes (four patients) and distant omental metastasis (one patient). In another patient, PET confirmed the presence of suspected M(1) disease in the liver. Posttreatment PET imaging was less useful. Nine patients had minimal residual PET activity at the primary site on the one-month follow-up PET study, but only three of these subsequently developed local recurrence. In addition, recurrences occurred in three patients (two local, one distant) of the six who had negative posttreatment PET studies. CONCLUSIONS: FDG-PET, in conjunction with CT scanning, provides additional staging information in cancer of the anal canal. This information may have implications for prognosis and radiotherapy planning. Posttreatment PET scans appear to be of little value in predicting durability of response.

Clinical use of fluorodeoxyglucose F 18 positron emission tomography for detection of renal cell carcinoma.

PURPOSE: We evaluate the role of fluorodeoxyglucose F 18 positron emission tomography (PET) in patients with renal cell carcinoma (RCC) by retrospective review. To our knowledge this series is the largest reviewing the use of PET in patients with RCC. MATERIALS AND METHODS: A total of 66 patients who underwent 90 PET scans for suspected or known RCC were identified. Dictated reports of PET, chest computerized tomography (CT), abdominal/pelvic CT and bone scan were examined with confirmation of results by histopathology or followup of at least 1 year. The accuracies of PET and conventional imaging modalities were compared. RESULTS: PET exhibited a sensitivity of 60% and specificity of 100% for primary RCC tumors (abdominal CT demonstrated 91.7% sensitivity and 100% specificity). For retroperitoneal lymph node metastases and/or renal bed recurrence, PET was 75.0% sensitive and 100.0% specific (92.6% sensitivity and 98.1% specificity for abdominal CT). PET had a sensitivity of 75.0% and a specificity of 97.1% for metastases to the lung parenchyma compared to 91.1% and 73.1%, respectively, for chest CT. PET had a sensitivity of 77.3% and specificity of 100.0% for bone metastases, compared to 93.8% and 87.2% for combined CT and bone scan. In 39 scans (32 patients) PET failed to detect RCC lesions identified by conventional imaging. CONCLUSIONS: The role of fluorodeoxyglucose F 18 PET in the detection of RCC is limited by low sensitivity. With superior specificity PET may have a complementary role as a problem solving tool in cases that are equivocal on conventional imaging.