Diffusion-weighted imaging in differentiating mid-course responders to chemotherapy for long-bone osteosarcoma compared to the histologic response: an update

Abstract

Background: Diffusion-weighted imaging (DWI) has been described to correlate with tumoural necrosis in response to preoperative chemotherapy for osteosarcoma.

Objective: To assess the accuracy of DWI in evaluating the response to neoadjuvant chemotherapy at the mid-course treatment of long-bone osteosarcoma and in predicting survival.

Materials and methods: We conducted a prospective single-centre study over a continuous period of 11 years. Consecutive patients younger than 20 years treated with a neoadjuvant regimen for peripheral conventional osteosarcoma were eligible for inclusion. Magnetic resonance imaging (MRI) with DWI was performed at diagnosis, and mid- and end-course chemotherapy with mean apparent diffusion coefficients (ADC) calculated at each time point. A percentage less than or equal to 10% of the viable residual tissue at the histological analysis of the surgical specimen was defined as a good responder to chemotherapy. Survival comparisons were calculated using the Kaplan-Meier method. Uni- and multivariate analyses with ADC change were performed by Cox modelling. This is an expansion and update of our previous work.

Results: Twenty-six patients between the ages of 4.8 and 19.6 years were included, of whom 14 were good responders. At mid-course chemotherapy, good responders had significantly higher mean ADC values (P=0.046) and a higher increase in ADC (P=0.015) than poor responders. The ADC change from diagnosis to mid-course MRI did not appear to be a prognosticator of survival and did not impact survival rates of both groups.

Conclusion: DWI at mid-course preoperative chemotherapy for osteosarcoma should be considered to evaluate the degree of histological necrosis and to predict survival. The anticipation of a response to neoadjuvant treatment by DWI may have potential implications on preoperative management.

Keywords: Bone neoplasm; Children; Diffusion-weighted imaging; Magnetic resonance imaging; Osteosarcoma; Therapeutic response.

Fig. 1

Osteosarcoma of the proximal tibial metaphysis with extension to physis, epiphysis and joint surface in a 9.5-year-old boy (patient 17). a−f Coronal planes acquired at T1-W (a, d), DWI at b0 value (b, e) and corresponding apparent diffusion coefficient (ADC) maps (c, f). Examples of ADC calculation (good responder) at MRI-1 (a, b, c) and MRI-2 (d, e, f): a region of interest is manually drawn around the tumour along its longer axis to calculate the mean ADC of the tumour. A qualitative assessment of the ADC map shows a decrease in signal intensity at mid-course chemotherapy

Fig. 2

Flow diagram of participants

Fig. 3

Box plots comparing apparent diffusion coefficient (ADC) values at MRI acquired at mid-course of chemotherapy (MRI-2). a−c Box plots compare ADC2 values (a), absolute differential ADC2−ADC1 values (b) and ratio (ADC2−ADC1)/ADC1×100 values (c). Good responders have higher mean ADC values and higher increases in ADC from initial to mid-course MRI than poor responders