The Committee on Human Research at three major pediatric oncology centers approved this retrospective evaluation. Pediatric radiologists at UCSF Children’s Hospital, Hospital for Sick Children, which is affiliated with the University of Toronto, and St. Jude Children’s Research Hospital reviewed their records of the last 11 years (1998–2009) and identified eight patients with biopsy-proven alveolar RMS and pancreatic metastases out of a total of 71 cases (males:females
34:37) of alveolar rhabdomyosarcoma. All clinical data and imaging studies of these patients were reviewed retrospectively, including patient’s age, gender, clinical presentation, primary tumor location, presence or absence of metastases at diagnosis, type of therapy, presence or absence of recurrence after therapy, metastases at time of recurrence, duration between initial diagnosis and imaging findings of pancreatic metastases and final outcome.
The eight subjects included three males and five females, ages 1.8 to 35.0 years (mean
4.4 years). Interestingly, all younger patients were females while the males in this series presented with disease in the pubertal and post-pubertal years. The characteristics of the patients are summarized in Table . The diagnosis of alveolar RMS was confirmed on histologic biopsy of the primary tumor. Medical history, treatment history and imaging studies were reviewed.
Synopsis of patient data including demographics, primary tumor, tumor recurrence, imaging findings and prognosis
Evaluations of imaging studies included the following:
Imaging studies at diagnosis of the primary tumor revealed that all eight patients received an MR and three had a CT of the primary tumor. In addition, all patients received a contrast-enhanced chest CT (CECT) at diagnosis. Abdominal axial contrast-enhanced CT scans covered the pancreas in accordance to the Children’s Oncology Group (COG) guidelines for initial staging in all the patients. Three patients received a PET and two received a PET-CT. Three patients didn’t receive any PET examination.
The patients were followed with MRI of the primary tumor and CECT of the chest at weeks 6, 19, and 34 during therapy and at the end of therapy at week 54 per COG protocols. In addition, abdominal CECT was obtained in all patients at weeks 6, 19, 34 and 54 except four instances, when non-enhanced abdominal CTs were obtained in two patients at weeks 6 and 34 of their respective follow-ups.
PET-CT studies were employed for four of these patients who were deemed to be high risk or for evaluating suspected widespread metastases for treatment planning. All imaging studies were retrospectively reviewed by two independent pediatric radiologists at each center concerning the presence, number, size, location and imaging characteristics of pancreatic metastases.
In acquiring the diagnostic-quality CTs associated with this study, the effective dose ranged between 1.76 and 24.7 mSv for all patients. The radiopharmaceutical 18F-FDG was intravenously injected at a rate of 0.21 mCi/kg of body weight (7.78 MBq/kg) with a mean activity of 14.37 mCi (531.69 MBq/kg) administered. Thus, based on the biodistribution of 18F-FDG and the ICRP internal dosimetry model, the radiation exposure of a patient who received the mean dose of 18F-FDG was 1.58 rem (12.2 mSv; http://www.internaldosimetry.com
; CDE Dosimetry Services, Inc. 2001). The combination of PET and CT provided a mean effective dose of 23.49 mSv (range 19.12 to 55.06 mSv).