Usefulness of increased 18F-FDG uptake for detecting local recurrence in patients with extremity osteosarcoma treated with surgical resection and endoprosthetic replacement

Objective To investigate the changes of increased F-18 fluorodeoxyglucose ( 18 F-FDG) uptake around the prosthesis and its ability to differentiate local recurrence from postsurgical change after endoprosthetic replacement in extremity osteosarcoma. Materials and methods A total of 355 positron emission tomography (PET)/computed tomography (CT) scans in 109 extremity osteosarcoma patients were retrospectively analyzed. All patients were followed up with 18 F-FDG PET/CT for more than 3 years after tumor resection. For semiquantitative assessment, we drew a volume of interest around the entire prosthesis of the extremity and measured the maximum standardized uptake value (SUVmax). Independent samples t test was used to compare SUVmax at each follow-up time. SUVmax at 3 months (SUV1) and SUVmax at the time of local recurrence in patients with recurrence or at the last follow-up in others (SUV2) were compared using the Mann–Whitney test. Diagnostic performances of PET parameters were assessed using ROC curve analyses. Results Nine patients (8 %) showed a local recurrence. Mean SUVmax at 3, 12, 24, and 36 months was 3.1 ± 1.5, 3.8 ± 1.9, 3.6 ± 1.9, and 3.7 ± 1.5 respectively. In ROC curve analysis, the combination of SUV2 >4.6 and ΔSUV >75.0 was a more useful parameter for predicting local recurrence than SUV2 or ΔSUV alone. The sensitivity, specificity, and accuracy for identifying local recurrence were 89, 76, 77 % for SUV2; 78, 81, 81 % for ΔSUV; and 78, 94, 93 % for the combined criterion respectively. Conclusion The combination of SUV2 and ΔSUV was more useful than the SUV2 or ΔSUV used alone for the prediction of local recurrence.