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 TI-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 ²⁰¹T1 in malignant bone and soft tissue tumors (MBST). Sixty-eight patients with MBST underwent ^99mTc-MIBI and ²⁰¹T1 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 ≥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 (ΔPI) and uptake ratios (ΔUR) calculated by 100 ′ [(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 ΔUR, and 74%, 74%, 74% in ΔPI, respectively. The area under the receiver operator characteristic curve (A_z of the ^99mTc-MIBI-ΔUR (0.923) was significantly higher than that of API (0.809, p = 0.025) but only marginally higher than that of the ²⁰¹T1-ΔUR (0.865, p = 0.079). A_z in ²⁰¹T1 (0.865) was not significantly different from that of ΔPI (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.