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

Objectives This study aimed to evaluate F-18 fluorodeoxyglucose (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).

Methods A total of 28 consecutive pediatric RMS (20 males, 8 female; mean age, 4.8 years, 10 embryonal，18 alveolar), in whom FDG PET/CT was performed at staging, evaluation of therapeutic effects and follow-up, were retrospectively included. FDG PET/CT was compared with MRI, 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.

Results 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 bone, muscle, brain, etc in 4 patients versus 16, 6, and 29, respectively, with CT or MRI. On the whole analysis, FDG PET/CT modified lymph node staging in 4 of 13 patients. The significant high SUV_max of primary tumor and more metastases were found in alveolar RMS(ARMS). In 4 patients (31%), modifications were made and comprised 1 local therapy change and 3 changes of systemic treatment as well. Four patients (4/11) achieved complete metabolic response on FDG PET/CT and 2 were partial responders on FDG PET/CT.

Conclusions FDG PET/CT is useful in staging and restaging pediatric RMS, especially for assessing lymph nodes and prostate involvement with potential therapeutic strategy alteration. The significant high SUV_max of ARMS and more metastases may indicate worse prognosis which needs further study. This study confirms that FDG PET/CT is also valuable in therapeutic assessment and follow-up.

Research Support National Natural Science Fund (grant 51233007，81271612 and 81401439), Shanghai Pujiang Program (grant 13PJD022), and Shanghai Health Bureau Fund (grant 20124016).