18F-fluorodeoxythymidine PET for evaluating the response to hyperthermic isolated limb perfusion for locally advanced soft-tissue sarcomas.

UNLABELLED Locally advanced soft-tissue sarcomas of an extremity can be treated either by amputation of the limb or by hyperthermic isolated limb perfusion (HILP) followed by resection of the tumor. In this study, the response to HILP was measured by PET with (18)F-fluorodeoxythymidine ((18)F-FLT). METHODS Ten patients with primary nonresectable soft-tissue sarcomas of an extremity underwent HILP with tumor necrosis factor-alpha and melphalan. Before and after HILP, all patients underwent PET with (18)F-FLT for response evaluation. RESULTS Before HILP, all tumors were clearly visible on (18)F-FLT PET; for the maximum standardized uptake value (SUV(max)), the mean was 3.5 (range, 1.0-6.7), and for the mean standardized uptake value (SUV(mean)), the mean was 1.9 (range, 0.7-2.7). After HILP, all but 1 tumor showed necrosis ranging from 10% to 95%. (18)F-FLT PET after HILP revealed significantly decreased uptake of the tracer. The mean SUV(max) decreased to 1.7 (P = 0.008), and the mean SUV(mean) decreased to 0.8 (P = 0.002). One small axillary lymph node metastasis was not visible on (18)F-FLT PET. CONCLUSION (18)F-FLT PET revealed high uptake in soft-tissue sarcomas. (18)F-FLT uptake was correlated with the mitotic index of the tumors (r = 0.82 and P = 0.004 for SUV(max); r = 0.87 and P = 0.001 for SUV(mean)). After HILP, the uptake of (18)F-FLT decreased significantly (P = 0.008 and P = 0.002 for SUV(max) and SUV(mean), respectively). Tumors with initially high (18)F-FLT uptake showed a better response to HILP (r = 0.64, P < 0.05). Software fusion of PET images with images from conventional imaging modalities revealed the heterogeneity of the tumors before and after HILP. Such data can help a surgeon in planning the resection of a tumor.