The study find that the retrospectively reviewed the data from 31 pediatric patients with pathologically confirmed YST who underwent 34 PET/CT studies for the purpose of staging or restaging. The PET/CT ;studies are read by two nuclear medicine doctors in consensus. Histopathology combined with clinical and imaging follow-up was take as the reference standard. The results of PET/CT are also compare with conventional imaging and α-fetoprotein (AFP); levels when available.
Clinical and imaging
Of the total 34 studies; six were perform for initial staging and the other 28 for posttherapy evaluation. FDG PET/CT is true-positive in all six staging studies, detect only a few more metastatic foci than conventional imaging, and change the therapeutic regimen in none of the six patients. Nevertheless; PET/CT showed high accuracy in the restaging group, with a sensitivity of 100% and specificity of 85.7%.
The treatment regimen is change in 46.4% of the patients in the restaging group according to the PET/CT study. In addition; PET/CT had higher accuracy than AFP levels in YST restaging. Overall; the per-study performance of PET/CT was a sensitivity of 100%, specificity of 85.7%, positive predictive value of 90.9%, and negative predictive value of 100%.
Negative predictive value
FDG PET/CT was only slightly superior to conventional imaging in staging YST in pediatric patients. However; PET/CT of posttherapy patients with YST showed high diagnostic accuracy and had a great impact on therapeutic management. alignant germ cell tumor (GCT) accounts for only 1–4% of malignant tumors in children;l in which yolk sac tumor (YST) is the most common subtype.
YST is generally believed to originate from primitive germ cells and usually occurs in testes, ovaries, and extragonadal locations including the anterior mediastinum, sacrococcygeal region; and pineal gland . Because of the endodermal origin of YST, the α-fetoprotein (AFP); level is high in most patients. Therefore, AFP value is recognize as an important biologic marker in the diagnosis; treatment evaluation, and follow-up of YST.
Chemotherapy after surgery
The prognosis of patients with YST is closely related to the staging of the tumor. Studies also indicate that children with stage I gonadal YST can be spared from undergoing chemotherapy after surgery . Therefore; accurate staging is important in guiding treatment and improving prognosis.
The use of FDG PET/CT; an imaging modal ity integrating functional metabolic imaging and anatomic localization, has been widely report for therapeutic monitoring and prognosis evaluation in pediatric lymphoma, neuroblastoma; soft-tissue sarcoma, and other malignant tumors. However, the application of PET/CT in pediatric YST has been report in only a few case series . In this study, we evaluated the utility of FDG PET/CT in staging and restaging of disease in infants and children with YST