Abstracts XIX Brazilian Congress of Nuclear Medicine

7. ONCOLOGY

Several studies have reported the use of [Tc-99m] sestamibi in the evaluation of tumor viability. The purpose of this study was to investigate the usefulness of this radiopharmaceutical in the evaluation of Ewing’s sarcoma and osteosarcoma response to preoperative chemotherapy in children and adolescents. Fourteen patients (pts) (8 males, 6 females; 6-17 years, mean 11.6 years), with biopsy-proven high grade osseous sarcomas (9 osteosarcomas and 5 Ewing’s sarcomas) were studied. The images were obtained before and after preoperative chemotherapy. Dynamic images were acquired at 2 seconds intervals for 1 minute immediately after the intravenous injection of 370-740 MBq (10 – 20 mCi) of [Tc-99m] sestamibi to assess tumor blood flow. Early planar images or whole body scans were obtained at 5 – 10 minutes and delayed images (whole body) after 30-60 minutes. Three pts were imaged after 2-3 hours. Tumor uptake of [Tc-99m] sestamibi before and after chemotherapy was graded visually using the 30-60 minutes images as follows: 0=absent or very mild, 1=mild, 2=moderate, 3=marked. The pts were divided into two groups based on the histopathological classification: good responders with 90% or higher of tumor necrosis and poor responders with less than 90% of tumor necrosis. All pts had uptake grade 2 or 3 prior to chemotherapy. After chemotherapy all eleven good responders had significant reduction of tumor uptake to grade 0. One poor responder with borderline amount of post-chemotherapy necrosis (88,4%) had reduction of uptake to grade 1. One of the 2 definitive poor responders (20% of necrosis) had a non-significant reduction of uptake to grade 2; however, the other poor responder (10% of necrosis) had a significant reduction to grade 0. These results support the concept that the reduction of [Tc-99m] sestamibi tumor uptake reflects the response to chemotherapy in most cases. This method was also able to detect two poor responders in this series. The reduction of uptake in a poor responder should be further investigated and may be related to the expression of the multidrug resistance glycoprotein P.

1.Cardiology |  2.Endocrinology | 3.Equipment: Quality Control | 4.Gastroenterology |  5.Infectious Diseases |  6.Nephro-Urology |  7.Oncology |  8.Orthopheadics | 9.PET/SPECT | 10.Pneumology |  11.Radiobiology |  12.Radiopharmacy |  13.Special Clinical Applications |  14.Neuropsychiatry |