MIDCOURSE TL-201 SCINTIGRAPHY TO PREDICT TUMOR RESPONSE IN BONE AND SOFT-TISSUE TUMORS

The purpose of this study was to assess the predictive power of (TI)-T -201 scintigraphy in the midcourse of chemotherapy for the final tumor response to chemotherapy in malignant bone and soft-tissue tumors. Me thods: The 21 patients studied with (TI)-T-201 scintigraphy were 14 ma les and 7 females (average age 39.8 +/- 22.1 yr; age range 8-74 yr). P lanar scintigraphy was performed 15 min after injection of 111 MBq 201 TI 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 (TI)-T-201 uptake ratio was calculated by dividing the count density of the lesion by that of the contralateral normal area. The percent reduction of the (TI)-T-201 uptake ratio calc ulated by 100 x [(prechemotherapy ratio - postchemotherapy ratio)/prec hemotherapy ratio] in the midcourse was compared with that after the f inal course of chemotherapy, and it also was compared with the histolo gic response. Results: In patients with histologically complete respon se [(CR), n = 6] and with partial response [(PR), n = 5], the percent reduction in (TI)-T-201 uptake ratio after three cycles of chemotherap y was 64.1% +/- 14.4% and 50.9% +/- 10.5%, respectively. In patients w ith histologically no change [(NC), n = 10], the percent reduction was 0.40% +/- 18.2% after the third cycle; -5.3% +/- 20.9% in four patien ts with full courses of chemotherapy (p < 0.0001 and p < 0.005 compare d with the CR and PR groups, respectively). After the final cycle of c hemotherapy, 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). Co nclusion: Thallium-201 scintigraphy performed in the midcourse of chem otherapy is predictive of the final response to chemotherapy that can be demonstrated histologically. Serial 201TI scintigraphy in the midco urse of chemotherapy is useful in assessing final chemotherapeutic res ponse in the early stage of chemotherapy, and it helps clinicians when choosing the most appropriate treatment strategies in patients with b one and soft-tissue tumors.