The current study was designed to evaluate the ability of thallium-201 scintigraphy to predict the response to preoperative chemotherapy in osteosarcoma, by comparing changes in thallium uptake ratio after chemotherapy to the tumor necrosis ratio.

Twelve osteosarcoma patients were included in this study. Thallium-201 scintigraphy was performed before and after preoperative chemotherapy, and the degree of tumor necrosis was estimated by histologic mapping postoperatively. To quantitatively determine thallium uptake, we drew a region of interest on the tumor side and on the contralateral normal side as a mirror image, and calculated the uptake ratio with dividing the gamma count in the tumor side by that of the normal side. We calculated these percent changes of thallium uptake ratio in the early and delayed phases, and compared these to the corresponding tumor necrosis ratio.

Percent changes in the thallium uptake ratio were found to be correlated with the tumor necrosis ratio (p<0.03). This correlation was found in both the early (p<0.03) and delayed phase (p<0.03); moreover the correlation coefficient in early phase (0.79) was greater than that in the delayed phase (0.67).

Thallium-201 scintigraphy could be effective at predicting the response to preoperative chemotherapy in osteosarcoma.