Prediction of final tumor response to preoperative chemotherapy by Tc-99m MIBI imaging at the middle of chemotherapy in malignant bone and soft tissue tumors: comparison with Tl-201 imaging.

The aim of this study was to assess the predictive power of 99mTc-MIBI scintigraphy performed in the middle of chemotherapy, for the final tumor response to chemotherapy, and compare it to that of (201)Tl in malignant bone and soft tissue tumors (MBST). Sixty-eight patients with MBST underwent 99mTc-MIBI and 201Tl scintigraphies at 15 min after tracer injection before the first, and after the third, chemotherapy cycles. After five cycles of chemotherapy and tumor resection, therapeutic effect was assessed by histopathology. Less than 90% and > or =90% necrosis were judged as poor and good response to chemotherapy, respectively. Tracers uptake ratios were calculated by dividing the lesion count density by that of the background. 99mTc-MIBI perfusion index was also calculated. The % reduction of the perfusion index (DeltaPI) and uptake ratios (DeltaUR) calculated by 100 x [(prechemotherapy value--postchemotherapy value)/prechemotherapy value] were compared with histologic response. The sensitivity, specificity, and accuracy for the prediction of effective chemotherapy in 99mTc-MIBI imaging were 80%, 95%, 88% in DeltaUR, and 74%, 74%, 74% in DeltaPI, respectively. The area under the receiver operator characteristic curve (A(z)) of the 99mTc-MIBI-DeltaUR (0.923) was significantly higher than that of DeltaPI (0.809, p = 0.025) but only marginally higher than that of the 201Tl-DeltaUR (0.865, p = 0.079). A(z) in 201Tl (0.865) was not significantly different from that of DeltaPI (0.809, p = 0.35). 99mTc-MIBI imaging performed in the middle of chemotherapy well predicts the final tumor response to chemotherapy in patients with malignant bone and soft tissue tumors.