Comparison of PET–CT and conventional imaging in staging pediatric rhabdomyosarcoma

Abstract

Purpose To compare PET-CT to conventional imaging (CI) in staging pediatric rhabdomyosarcoma (RMS). Subjects and Methods Thirty subjects with RMS, median age 7.3 years, underwent PET-CT before therapy. PET-CTs and CI were independently reviewed by two radiologists and two nuclear medicine physician to determine the presence of nodal, pulmonary, bone, bone marrow and other sites of metastasis. Accuracy, sensitivity and specificity of PET-CT for detecting metastases was compared to CI using biopsy and clinical follow-up as reference standards. Maximum standardized uptake values (SUVmax) of primary tumors, lymph nodes and pulmonary nodules were measured. Results Primary tumors had an average SUVmax of 7.2 (range, 2.5-19.2). Accuracy rates for 17 subjects with nodal disease were 95% for PET-CT and 49% for CI. PET-CT had 94% sensitivity and 100% specificity for nodal disease. Of 7 pulmonary nodules detected by CI, 3 were not identified by PET-CT, 2 were indeterminate by PET-CT, and 1 was malignant with a SUVmax (3.4) > twice that of benign nodules. Two subjects had bone disease; both were identified by PET-CT but only 1 by CI. Four subjects had bone marrow disease, 2 had positive PET-CTs but none had positive CI. Two subjects had soft tissue metastases detected by PET-CT but not CI. Conclusion PET-CT performed better than CI in identifying nodal, bone, bone marrow, and soft tissue disease in children with RMS. CI remains essential for detection of pulmonary nodules. We recommend PET-CT for routine staging of children with RMS. CI with Tc99m bone scan can be eliminated.

Diagnostic imaging of benign and malignant neck masses in children—a pictorial review

“…Positron Emission Tomography (PET) CT has also shown promise in staging these patients (3,7,19,(24)(25)(26).…”

Value of18F-FDG PET and PET/CT for Evaluation of Pediatric Malignancies

“…It was recommended that bone scans be omitted if bone sarcomas are evaluated with 18 F-FDG PET (81). The appropriateness of this recommendation was confirmed by studies that evaluated rhabdomyosarcomas and bone sarcomas separately: for detection of bone metastases in rhabdomyosarcomas, 18 F-FDG PET/CT showed a sensitivity of 100%, compared with 66% for conventional imaging modalities, including radiography, CT, MR imaging (79), or bone scintigraphy alone (2,71). For detection of bone metastases in Ewing sarcomas, 18 F-FDG PET showed a sensitivity of 88%, compared with 37% for conventional imaging modalities (78).…”

“…The presence of regional lymph node metastases is a strong prognostic factor in rhabdomyosarcoma patients (72,86). 18 F-FDG PET/CT was more sensitive (94%-100%) and more accurate (95%-100%) than conventional imaging (75%-94% and 49%-88%, respectively) for detection of lymph node metastases (71,79). Integrated 18 F-FDG PET/CT was also more accurate than 18 F-FDG PET alone (96% vs. 86%) (77).…”

“…The presence of metastases is common in sarcomas and is associated with poor prognosis (71,72). Typical sites to be investigated with imaging tests are lymph nodes (more common in rhabdomyosarcomas, less common in bone sarcomas), lung, and bone (73)(74)(75).…”

Childhood extracranial neoplasms: the role of imaging in drug development and clinical trials

“…This is exemplified in the lungs where conventional, higher-dose CT remains more sensitive in the detection of small lung nodules (<5 mm) [128]. Unfortunately, the resolution of the PET camera is fundamentally limited by positron range, although effects that degrade spatial resolution can be reduced or eliminated by meticulous camera design [129].…”