Early evaluation of the response to chemotherapy of sarcomas in children using 99mTc-SESTAMIBI

Several reports in the literature have shown that the radiopharmaceutical 99mTc-sestamibi is a marker of tumor viability. Aim: Evaluate the response of bone and soft tissue high-grade sarcomas to pre-operative chemotherapy in children and young adults, using 99mTc-sestamibi before, during and after chemotherapy. Materials and Methods: Forty-four patients (28 males, 16 females; 6-20 years, mean age 12.3 years) with biopsy-proven osteosarcoma (27 patients) and Ewing's sarcoma (17 patients) were studied by planar imaging with 99mTc-sestamibi before and after preoperative chemotherapy. Ten patients were also studied during chemotherapy. A dynamic study of 1 frame/ 2 seconds for 1 minute was obtained immediately after an intravenous injection of 370-740 MBq of 99mTc-sestamibi to assess regional blood flow to the tumor. Static images at 5, 10 and 60 minutes after tracer injection were also performed. Tumor blood flow and uptake of 99mTc-sestamibi were visually compared with the contra-lateral side and graded as follows: 0 = absent, 1 mild, 2 = moderate, 3 = marked 99mTc-sestamibi uptake. Histopathological classification divided the specimens into two groups: good responders with 90% or greater cellular necrosis and poor responders with less than 90% cellular necrosis. Results: All patients had uptake grade 2 or 3 prior to chemotherapy. All the good responders (34/44) had reduction of tumor uptake to grades 0 and 1 after chemotherapy. Among the poor responders, 6/10 remained with high tumor uptake (grades 2 and 3) after chemotherapy, while 4/10 had reduction of tumor uptake (grades 0 and 1) after chemotherapy. The 10 patients that were also imaged at midpoint of chemotherapy were all good responders and presented reduction of tumor uptake during and after chemotherapy. Conclusion: These results support the concept that the tumor uptake correlates well with histopathological response of bone and soft tissue high-grade sarcomas. The reduction of uptake in some poor responders should be further investigated and may be related to the expression of the multidrug resistance glycoprotein P. Uptake reduction is progressive throughout chemotherapy and imaging with 99mTc-sestamibi at midpoint can predict the degree of uptake reduction at the end of chemotherapy