Imaging Assessment of Tumor Response: Past, Present and Future

Abstract

Anatomical response assessment criteria have been in use for decades, with the WHO guidelines being replaced by Response Evaluation Criteria in Solid Tumors (RECIST), updated in 2009 to RECIST 1.1. These methods rely on a change in size of a tumor as the main response criteria, but newer cytostatic agents tend to target tumor function at a molecular level before changing the size of a lesion. Recent modifications, such as the Choi criteria, have improved assessment by taking into account density of tumor, but all of these criteria fail to utilize functional imaging parameters, which are becoming increasingly available, including perfusion CT, perfusion MRI, diffusion-weighted imaging, magnetic resonance spectroscopy, dynamic contrast-enhanced ultrasound and combined PET/computed tomography. Developments in these modalities and standardization of imaging acquisition will help to optimize the next set of response criteria, with inclusion of multiparametric, functional modalities, evaluating tumors at the same molecular level at which they are being targeted by therapeutic agents.

Diffusion-Weighted Magnetic Resonance Imaging for Early Detection of Chemotherapy Resistance in Non-Small Cell Lung Cancer

“…Until now, the evaluation of chemotherapy resistance in lung cancer mainly relies on RECIST system [16,17], which needs a long time before the morphology changes appears [18]. Clinically, CT images are used for the assessment of the efficacy firstly after the end of 2 cycles of chemotherapy [4].…”

Simultaneous PET–MRI in oncology: a solution looking for a problem?

“…In recent years there have been dramatic increases in the range and quality of information available from these non-invasive methods so that many potentially valuable imaging metrics are now available to assist in diagnosis, determine extent of disease, measure tumor size, and predict treatment response [see, e.g., 1]. Depending on the modality, quantitative information can be obtained that reports on anatomical (MRI, CT, US), physiological (MRI, CT, PET, US), cellular (MRI, PET), and even molecular (MRI, PET, SPECT, US) events.…”

Evaluation of a Novel Macromolecular Cascade-Polymer Contrast Medium for Dynamic Contrast-Enhanced MRI Monitoring of Antiangiogenic Bevacizumab Therapy in a Human Melanoma Model

“…Published studies on the applicability of DCE-MRI with clinically available small-molecular contrast medium (molecular weight <1 kDa) for monitoring angiogenesis and anti-angiogenic therapies reveal controversial results with regard to the pathophysiologic correlate and validity of the assessed noninvasive parameters of microcirculation (28,29). Additionally, a lack in standardization of acquisition and postprocessing protocols (30) may be in part responsible that some investigators had difficulties to duplicate each others' results (31). Alternatively, macromolecular contrast media (molecular weight >60 kDa) have been proposed for monitoring antiangiogenic treatment because they follow a primarily intravascular distribution profile with a pronounced extravasation through the hyperpermeable endothelium of angiogenically active tissues under VEGF stimulation, allowing for a sensitive assessment of angiogenic activity in tumors (29,32).…”