18F-FDG PET/CT is useful in initial staging, restaging for pediatric rhabdomyosarcoma

This study aimed to evaluate 18F-fluordeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) as an adjunct to CT and/or magnetic resonance imaging (MRI) in the staging and follow-up of pediatric rhabdomyosarcoma (RMS).

A total of 28 consecutive pediatric RMS (20 males, 8 females; mean age: 4.8 years, 10 embryonal, 18 alveolar), in whom FDG PET/CT was performed at staging (13 patients), to evaluate the therapeutic effects and to follow-up (15 patients), were retrospectively included. FDG PET/CT was compared with MRI or CT performed with a less than a 10-day interval for initial staging in 13 patients. Histological data and follow-up (mean, 18 months) were considered as the standard of reference for result interpretation.

At staging, FDG PET/CT and CT/MRI were equally effective in the detection of the primary RMS (accuracy, 100%). FDG PET/CT revealed metastases in lymph nodes, prostate, intestinal wall, chest wall and the peritoneum in 5 patients missed by CT or MRI, and found 41positive lymph node territories in 6 patients, 8 lung metastases in 3 patients and 40 lesions located in other anatomical regions (muscle, brain, etc.) in 4 patients versus 16, 6, and 29 for CT or MRI. In 4 patients (31%), modifications were made and comprised 1 local therapy change and 3 changes of systemic treatment as well. Follow-up time ranged from 3 to 48 months, with a median follow-up time of 18 months in 15 patients for evaluation of therapeutic effects. Alveolar RMS (ARMS) had significantly high SUVmax, and more metastases was found in ARMS.

18F-FDG PET/CT may be useful in staging and restaging pediatric RMS, especially for assessing secondary lesions with potential therapeutic strategy alteration. The significant high SUVmax of ARMS and more metastases may indicate worse prognosis which needs further study. This study confirms that 18F-FDG PET/CT is also valuable in therapeutic assessment and follow-up.