CASE 2
By: Dr. Mervat M. Aboualkheir; Dr. Muhammad Salman; Dr. Shankar Raja; and Dr. Tuli Mahmoud Madhehebu.
HISTORY: Male child – 5-year-old with history of Ewing’s sarcoma, presented with right hip pain and right sided pelvis swelling
What are the findings in following PET-CT images?
What are the possible causes of abnormal uptake on PET-CT?
FINDINGS:
Initial FDG PET-CT scanned on October 2015 showed a right iliac fossa osseous component and an associated large ilio-psoas soft tissue mass which was mildly FDG avid and heterogeneous pattern (SUV max 3.9); and associated with mild hypermetabolic ipsilateral pelvic lymph nodes; no other loco-regional or distant hypermetabolic lesions suggesting metastases were observed.
F/u PET scan- Post- chemo showed interval resolution of previously noted heterogeneous hypermetabolism involving the primary site in right iliac fossa with persistent residual soft tissue morphologically; indicating complete metabolic response and partial morphologic response. Pulmonary nodules were not FDG avid.
DIAGNOSIS:
Ewing's sarcoma with metastasis.
Representative transverse slices (fusion PET-CT) A. and B. right iliac tumor and C. showing pulmonary nodules.
PEARLS AND DISCUSSION:
Current standard of management of Ewing’s sarcoma entails morphologic (MRI/CT) as well as functional imaging with PET-CT to evaluate metabolically active tumor burden at the primary site, metachronous lesion as well as distant metastases. PET-CT is also useful for prognostication (1).
Teaching Points:
FDG-PET is an excellent tool for monitoring the response to chemo-radiotherapy; as illustrated in this patient there was an early complete metabolic response but partial morphologic response.
PET is very sensitive and accurate for response therapy evaluation, showing significant metabolic response even after 1 or 2 cycles of chemotherapy while morphologic imaging modalities (MRI and CT) often lags PET metabolic response even up to few months, by size criteria (RECIST and WHO criteria for response therapy evaluation.
FURTHER READING:
The importance of PET/CT in the evaluation of patients with Ewing tumors. Júlio Brandão Guimarães,1 Letícia Rigo,2 Fabio Lewin et al. Radiol Bras. 2015 May-Jun; 48(3): 175–180.
Impact of whole-body MRI and FDG-PET on staging and assessment of therapy response in a patient with Ewing sarcoma. Furth C, Amthauer H, Denecke T, Ruf J, Henze G, Gutberlet M. Pediatr Blood Cancer 2006;47(5):607–611.
