Multiparametric magnetic resonance imaging for radiotherapy response evaluation in high-risk soft tissue sarcoma: A pilot study

TL;DR

This pilot study investigates the use of multiparametric MRI to evaluate treatment response in high-risk soft tissue sarcomas, but finds no clear link between MRI changes and tumor cell viability.

Contribution

The study provides new insights into the repeatability and variability of qMRI parameters in soft tissue sarcomas during treatment.

Findings

ADC and T2 showed low repeatability, while Ktrans had higher repeatability.

qMRI parameters showed heterogeneous changes across patients.

No significant association was found between qMRI changes and tumor cell viability.

Abstract

Soft tissue sarcomas (STS) are rare mesenchymal tumors for which no clinically validated quantitative magnetic resonance imaging (qMRI) parameters exist yet.

This study explores repeatability and association with histopathology of qMRI parameters during and after neo-adjuvant angiogenesis inhibition (oral pazopanib) and radiotherapy for localized, high-risk STS.

For fifteen patients, qMRI parameters, including apparent diffusion coefficient (ADC), volume transfer constant (Ktrans) and T2 relaxation times were acquired twice at baseline (B1 and B2), twice during neo-adjuvant treatment and pre-surgery. For all three parameters, the mean was determined per tumor. Subsequently, repeatability coefficient (RC or %RC) was assessed from B1 and B2 mean values. Mixed models were estimated to study the association between percentage viable cells from histopathology and absolute change from baseline (ΔqMRI) for ADC mean and percentage change from baseline (%ΔqMRI) for T2 and Ktrans at each time point.

RC was 0.17 × 10-3 mm2/s for ADC and %RC was, 5 % and 65 % for T2 and Ktrans, respectively.

The changes in mean ADC and T2 showed both increases and decreases at each timepoint, whereas mean Ktrans predominantly showed decreases. ΔqMRI for ADC mean, %ΔqMRI for T2 mean and %ΔqMRI for Ktrans mean showed no statistically significant association with % viable cells.

This pilot study reported relatively low repeatability coefficients for ADC and T2 and a higher repeatability coefficient for Ktrans and showed heterogeneous changes in qMRI parameters in fifteen STS patients, however with no association between these parameters and percentage viable cells.

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