Midcourse Thallium-201 Scintigraphy to Predict Tumor Response in Bone and Soft-Tissue Tumors

The purpose of this study was to assess the predictive power of 201TI scintigraphy in the midcourse of chemotherapy for the final tumor response to chemotherapy in malignant bone and soft-tissue tumors. The 21 patients studied with 201TI scintigraphy were 14 males and 7 females (average age 39.8+/-22.1 yr; age range 8-74 yr). Planar scintigraphy was performed 15 min after injection of 111 MBq 201TI before chemotherapy, after the third chemotherapy cycle (midcourse) in all 21 patients and after the final chemotherapy cycle but before surgery in 11 patients. The 201TI uptake ratio was calculated by dividing the count density of the lesion by that of the contralateral normal area. The percent reduction of the 201TI uptake ratio calculated by 100 x [(prechemotherapy ratio - postchemotherapy ratio)/prechemotherapy ratio] in the midcourse was compared with that after the final course of chemotherapy, and it also was compared with the histologic response. In patients with histologically complete response [(CR), n=6] and with partial response [(PR), n=5], the percent reduction in 201TI uptake ratio after three cycles of chemotherapy was 64.1%+/-14.4% and 50.9% +/-10.5%, respectively. In patients with histologically no change [(NC), n=10], the percent reduction was 0.40%+/-18.2% after the third cycle; -5.3%+/-20.9% in four patients with full courses of chemotherapy (p < 0.0001 and p < 0.005 compared with the CR and PR groups, respectively). After the final cycle of chemotherapy, the percent reduction in 201TI uptake ratio was 68.6%+/-14.7%, 56.2%+/-6.1% and -0.3%+/-17.2% in the CR, PR and NC groups, respectively (NC versus CR, p < 0.0005; NC versus PR, p < 0.005). Thallium-201 scintigraphy performed in the midcourse of chemotherapy is predictive of the final response to chemotherapy that can be demonstrated histologically. Serial 201TI scintigraphy in the midcourse of chemotherapy is useful in assessing final chemotherapeutic response in the early stage of chemotherapy, and it helps clinicians when choosing the most appropriate treatment strategies in patients with bone and soft-tissue tumors.