Purpose: Tc-99m-methoxyisobutylisonitrile (MIBI) accumulates in only viable cells. In patients with bone and soft tissue sarcomas, preoperative chemotherapy is essential and the early prediction of the tumor response to chemotherapy would be beneficial for the planning of treatment strategy. The purpose of this study was to assess whether the change of Tc-99m-MIBI images from the prechemotherapy state to the early to midportion of chemotherapy can predict the final histopathological tumor response as accurately as the change of imaging after completion of chemotherapy.
Methods: Seventy-three patients with bone and soft tissue sarcomas underwent Tc-99m-MIBI scintigraphy before chemotherapy and at least 2 times after the second or third or fifth course of chemotherapy. The changes of the tracer uptake (DeltaUR) and perfusion (DeltaPI) from prechemotherapy to postchemotherapy were compared with histologic response.
Results: The sensitivity, specificity, and accuracy for the prediction of effective chemotherapy in DeltaPI were 88%, 83%, 85% after second, 85%, 72%, 78% after third, and 81%, 71%, 76% after 5th chemotherapy, and those in DeltaUR were 88%, 83%, 85% after 2nd, 85%, 92%, 89% after 3rd, and 94%, 77%, 85% after fifth chemotherapy, respectively. The area under the receiver operator characteristic curve of the DeltaPI after second, third, and fifth chemotherapy were similarly good (0.842, 0.858, 0.811, respectively) and those of DeltaUR were similarly excellent (0.915, 0.936, 0.931, respectively).
Conclusion: In patients with bone and soft tissue sarcomas, the change of Tc-99m-MIBI images from prechemotherapy to early to middle of chemotherapy can predict the final histopathological tumor response to chemotherapy as accurately as the change of Tc-99m-MIBI images from prechemotherapy to the completion of the preoperative chemotherapy.