Combination of ¹⁸F-FDG PET/CT and Diffusion-Weighted MR Imaging as a Predictor of Histologic Response to Neoadjuvant Chemotherapy: Preliminary Results in Osteosarcoma

Abstract

We evaluated the potential of 18 F-FDG PET/CT and diffusionweighted imaging (DWI) to monitor the histologic response in patients with extremity osteosarcoma receiving neoadjuvant chemotherapy, using sequential PET/CT and MR imaging. Methods: We prospectively registered 28 patients with high-grade osteosarcoma treated with 2 cycles of neoadjuvant chemotherapy and surgery. All patients underwent sequential 18 F-FDG PET/CT and MR imaging before (PET/MR1) and after neoadjuvant chemotherapy (PET/MR2). Maximum standardized uptake value (SUV), tumor volume based on MR imaging (MRV), and the mean apparent diffusion coefficient (ADC) values were measured on PET/MR1 (SUV1, MRV1, and ADC1) and PET/MR2 (SUV2, MRV2, and ADC2). The percentage changes in maximum SUV (ΔSUV), MRV (ΔMRV), and ADC (ΔADC) were calculated, and the correlations among these parameters were evaluated. After surgery, the effects of neoadjuvant chemotherapy were graded histopathologically: grades III and IV (necrosis of $ 90%) indicated a good response, and grades I and II (necrosis of , 90%) indicated a poor response. The optimum cutoff values of ΔSUV, ΔMRV, ΔADC, and their combination for predicting histologic response were assessed by single-and multi-receiver-operating-characteristic curve analysis. Results: Twenty-seven patients were enrolled in the present study after 1 patient with inadequate acquisition of MR imaging was excluded. ΔSUV and ΔADC negatively correlated with each other (r 5 20.593, P 5 0.001), and ΔMRV did not correlate with ΔSUV or ΔADC. The cutoff value, sensitivity, specificity, and accuracy for predicting good histologic response were # 252%, 67%, 87%, and 78%, respectively, for ΔSUV and . 13%, 83%, 73%, and 78%, respectively, for ΔADC. However, ΔMRV did not predict histologic response. Sensitivity, specificity, and accuracy were 83%, 87%, and 85%, respectively, using the combined criterion of ΔSUV # 231% and ΔADC . 13%. Conclusion: In the current preliminary study, both PET/CT and DWI are useful for predicting histologic response after neoadjuvant chemotherapy in osteosarcoma. Combining PET/CT and DWI may be an effective method to predict the histologic response of patients to neoadjuvant chemotherapy.

Value of diffusion-weighted imaging for evaluating chemotherapy response in osteosarcoma: A meta-analysis

“…Certain studies revealed that an increased ADC following neoadjuvant chemotherapy is associated with good histological response (24,25,27,29,30). However, there have been conflicting results.…”

“…Subsequently, 3 articles were excluded after reviewing the whole article (23)(24)(25). Five articles with 106 patients who fulfilled all of the inclusion criteria were selected for the meta-analysis (Table I) (26)(27)(28)(29)(30). The detailed procedure of study selection and its exclusion reasons in the meta-analysis is presented in Fig.…”

“…The combination of PET/CT and DWI may yield varied biological information, such as changes in glucose metabolism and cellularity, which means that it has the potential to overcome the functional limitations of individual PET/CT and DWI. Several studies have suggested 40-60% of the standardized uptake value (SUV) ratio as the PET/CT cutoff point for a good response to neoadjuvant chemotherapy of osteosarcoma (12,27,31), but the optimal ADC cutoff point for good responders to neoadjuvant chemotherapy of osteosarcoma has yet to be reported. Furthermore, there is no standard means to measure ADC values.…”

“…Recently, PET or PET/CT has become one of the most intensively-investigated imaging modalities for the monitoring of preoperative chemotherapy effects (12). Byun et al (27) reported the equivalent potential of PET/CT and DWI to predict the histologic response to neoadjuvant chemotherapy in 28 patients with extremity osteosarcoma, using sequential imaging capture. The combination of PET/CT and DWI may yield varied biological information, such as changes in glucose metabolism and cellularity, which means that it has the potential to overcome the functional limitations of individual PET/CT and DWI.…”

A Novel System for the Surgical Staging of Primary High-grade Osteosarcoma: The Birmingham Classification

“…The ability of functional imaging to predict response to chemotherapy in osteosarcomas becomes more vital with our findings, and several groups are investigating the role of PET-CT or functional MRI to preoperatively predict response to neoadjuvant chemotherapy, which may aid the preoperative planning of margins in light of this classification system [8,14]. In particular, it may affect the decision as to the type of surgery planned if the margins are likely to be less than 2 mm and the chemotherapy response is poor because of the probable higher rate of LR after a closer margin.…”