Early response monitoring to neoadjuvant chemotherapy in osteosarcoma using sequential 18F-FDG PET/CT and MRI

Objectives We evaluated the potential of sequential 18F-FDG PET/CT and MRI (PET/MRI) after 1 cycle of neoadjuvant chemotherapy to predict a poor histologic response in osteosarcoma.

Methods A prospective study was conducted on 30 patients with osteosarcoma treated with 2 cycles of neoadjuvant chemotherapy and surgery. All patients underwent PET/MRI before, after 1 cycle, and after the completion of neoadjuvant chemotherapy, respectively. Imaging parameters [maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and tumor volume based on magnetic resonance (MR) images (MRV)] and their % changes were calculated on each PET/MRI dataset and histological responses were evaluated on the postsurgical specimen.

Results A total of 17 patients (57%) exhibited a poor histologic response after 2 cycles of chemotherapy. Unlike the little volumetric change in MRI, PET parameters significantly decreased after 1 and 2 cycles of chemotherapy, respectively. After 1 cycle of chemotherapy, SUVmax, MTV, and TLG predicted the poor responders. Among these parameters, either MTV ≥ 47 mL or TLG ≥ 190 g after 1 cycle of chemotherapy was significantly associated with a poor histologic response on multivariate logistic regression analysis (OR 8.98, p = 0.039). The sensitivity, specificity, and accuracy of these parameters were 71%, 85%, and 77%, and 71%, 85%, and 77% respectively.

Conclusions The histologic response to neoadjuvant chemotherapy in osteosarcoma can be predicted accurately by FDG PET after one course of chemotherapy. Among PET parameters, MTV and TLG were independent predictors of the histologic response.