¹⁸F-FDG Uptake During Early Adjuvant Chemotherapy Predicts Histologic Response in Pediatric and Young Adult Patients with Osteosarcoma.

Abstract

The purpose of this study was to determine the relationship of ¹⁸F-FDG uptake in the primary tumor at diagnosis, during therapy, and after therapy with a histologic response and event-free survival in pediatric and young adult patients with osteosarcoma (OS). <b>Methods:</b> Serial (baseline and 5 and 10 wk after start of therapy) ¹⁸F-FDG PET/CT imaging was performed in patients with newly diagnosed OS treated uniformly in a therapeutic trial at a single institution. Whole-body images were obtained approximately 1 h after injection of ¹⁸F-FDG. Logistic regression was used to study the association of tumor uptake and changes in SUV_max between 0, 5, and 10 wk for both clinical endpoints. <b>Results:</b> Thirty-four patients (17 males; median age, 12.2 y; age range, 6.8-19.1 y) underwent PET imaging; 25 (74%) had localized disease. Primary tumor locations included the femur (<i>n</i> = 17; 50%), tibia (<i>n</i> = 9; 26%), and humerus (<i>n</i> = 5; 15%). Logistic regression showed that SUV_max at 5 wk (<i>P</i> = 0.034) and 10 wk (<i>P</i> = 0.022) and percentage change from baseline at 10 wk (<i>P</i> = 0.021) were highly predictive of a histologic response. Using SUV_max of 4.04 at week 5, SUV_max of 3.15 at week 10, and 60% decrease from baseline at week 10 as cutoff values, we determined that the respective sensitivities were 0.93, 0.93, and 0.79 and that the respective specificities were 0.53, 0.71, and 0.76. <b>Conclusion:</b> SUV_max on routine images at 5 or 10 wk and percentage change in SUV_max from baseline to week 10 were metabolic predictors of a histologic response in OS. These findings may be useful in the early identification of patients who are responding poorly to therapy and may benefit from a change in treatment.