Metastatic disease to the liver is common and is cause of morbidity and mortality. In this talk, we will discuss the MR imaging techniques available to assess the response liver metastases to treatment. In particularly, we will discuss the use of diffusion-weighted MRI and dynamic contrast enhanced MRI. The potential of using MRI to assess the effects of treatment on the liver will be discussed. The challenges of evaluating response to new immunotherapies will also be highlighted.
In patients with cancer, metastatic disease to the liver is common, particularly from colorectal, neuroendocrine and breast cancers. Conventional morphological imaging using CT and MRI relies on using size measurement criteria (e.g. RECIST 1.1) for assessment treatment response. However, novel therapeutics may be effective without causing a significant reduction in tumour size. Hence, other methods to quantify therapeutic response is desired.
Clinical multi-parametric MRI may be applied to study different aspects of tumour biology, including angiogenesis and perfusion (dynamic contrast enhanced MRI), cellularity and microstructural organisation (diffusion-weighted imaging), tumour metabolism (MR spectroscopy), associated macromolecules (magnetisation transfer) and tissue magnetic relaxivity (e.g. T1 measurement). These methods have been used in research and clinical practice to assess the response of liver metastases to treatment.
Of these, diffusion-weighted imaging and dynamic contrast enhanced MRI have been most widely investigated. However, applying these techniques in a multi-centre setting can still be challenging and poses a translation gap for their wider adoption. Knowledge of measurement repeatability, process of quality assurance and quality control, as well as careful technical implementation will help to enhance clinical utility.
There is potential for using MR imaging to assess the effects on treatment on the normal liver. For example, in using selective internal radiotherapy, MR imaging is helpful in identify the onset of sinusoidal obstruction syndrome, which can be difficult to recognise on conventional CT imaging.
One of the current challenges in response assessment is to evaluate treatment response to immunotherapy. The potential for pseudo-progression and hyper-progression on such treatment requires accurate identification of patients that are not benefitting from treatment, so that there can be early termination of ineffective treatment and switching to a new therapy with the aim of maintaining patients in the best health for as long as possible.
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