Abstract
Background
Bone lesions in Ewing's sarcoma (ES/PNET) have been traditionally diagnosed with bone Scan. PET-scan is emerging as a promising investigative modality for detection of metastatic lesions. In this prospective study, we compare the utility of both to detect the metastatic sites.
Methods
One hundred and seventy five histologically proven cases of ESPNET from 2004-2009 were prospectively staged with bone scan and PET-scan with Breath- hold CT scan- thorax. The diagnostic value of PET-scan to pick up metastatic lesions was compared with bone scan.
Results
The site of primary disease was axial in 62(35.4 %) patients, appendicular in 94(53.7 %) patients, and extraskeletal in 19 (10.8 %) patients. 24(13.7 %) patients were metastatic at presentation, while 151(86.2 %) patients had localized disease. In all patients with localized disease, bone scan did not detect any lesion other than that detected on PET-scan. In metastatic patients, PET-scan detected 12 patients with lymph node involvement which were not detected by bone scan, 10 patients were found to have lung metastasis by PET scan with breath-hold CT thorax, bony metastases were seen in two patients where the number and site of lesions were same in both PET and bone scan. In 19 patients with extraskeletal PNET, PET scan detected primary lesion in all while the bone scan was non-avid in any of these.
Conclusion
PET- Scan was able to detect all the bony lesions picked up by bone scan at baseline in newly diagnosed patients of PNET/ES. Furthermore, PET-scan was able to detect extra-skeletal sites of metastases. We conclude that PET scan may obviate the need of bone scan in the diagnostic work up of patients with Ewing's sarcoma.
