[201Tl scintigraphic evaluation of tumor mass and viability of bone and soft-tissue tumors].

To characterize 201Tl uptake in patients with bone and soft-tissue tumor, we studied 49 patients with surgically proven tumors and one patient with a tumor diagnosed arteriographically. In 37 of our 50 patients, the tumor was evaluated with 201Tl and arteriography. Moreover, in 14 of patients with pre-operative chemotherapy, pathologic changes were graded on the basis of percent tumor necrosis as defined histologically. The percent tumor necrosis histologically was compared with changes in the scintigraphic and conventional angiographic studies. Radiologic comparisons demonstrated a high degree of correlation with images of 201Tl and both arterial and blood pool phase of 99mTc-HMDP. Ninety-six percent of 28 malignant tumors had positive 201Tl uptake. None of the patients showed any thallium accumulation in the soft tissues or skeleton adjacent to the lesion. Activity of 201Tl was mainly dependent upon a tumor blood flow and a vascular density. In of 14 cases with the preoperative chemotherapeutic treatment, 201Tl scintigraphic changes showed concordance with % tumor necrosis. Thallium-201 was superior to 99mTc-HMDP in predicting tumor response to chemotherapy. Interestingly, delayed images of 99mTc-HMDP of 5 responders with > 90% tumor necrosis showed decreased uptake in the adjacent bone to the tumor mass lesions. It seems to be quite all right to consider that a major determinant of 201Tl uptake is intratumoral angiogenecity, which is closely connected with tumor viability. Therefore, 201Tl is a sensitive radiopharmaceutical for detection of vascular rich bone and soft-tissue tumors, and appears to be a simple and an accurate test for evaluating the response to specific therapeutic regimens of malignant bone and soft-tissue tumors.