An imaging biomarker is a biologic feature, or a biomarker detectable in an image. Cardinal physiological features of tumours that occur as a result of interactions between cancer cells, stromal cells and secreted factors and cytokines and how they change with treatment, provide the opportunity to detect changes in the tumour microenvironment prior to any morphological change.
Functional magnetic resonance (MR) encompasses a spectrum of techniques that depict physiological and molecular processes before morphological changes are visible on conventional imaging. As the understanding of the pathophysiological and biomolecular processes involved in breast malignancies evolves, newer functional MR techniques can be employed that define early predictive and surrogate biomarkers for monitoring a response to chemotherapy.
Magnetic resonance imaging (MRI) of the breast has an established role in assessing response to neoadjuvant chemotherapy and provides better monitoring of the chemotherapeutic effect than clinical breast examination, mammography and ultrasound, especially in non-mass lesions and tumours that have fragmented into many foci. However, in the overall spectrum there is no definite advantage of MRI assessment over ultrasound and more studies at a larger scale are needed.
More complex functional MRI techniques offer to quantify changes in tumour microvasculature, cell density, hypoxia, metabolism and stiffness and therefore provide early predictive and surrogate biological biomarkers for monitoring response to chemotherapy. Through sequential imaging, the tumour response can be assessed and non-responders can be identified early to enable alternative therapies to be considered.
This E-learning module summarises the functional MR biomarkers of response in patients with breast cancer that are currently available and under development. The author describes the current state of each biomarker and explores their potential clinical uses and limitations in assessing treatment response. With the aid of selected interesting cases, biomarkers related to dynamic contrast-enhanced MRI, diffusion-weighted MRI, MR spectroscopy and multiparametric MRI are described and illustrated.
Ongoing research and recent technical advances indicate that the prospects for substantial improvements in monitoring the therapeutic response as well as for improvement of early detection and accurate diagnosis of breast cancer with functional MRI are promising, with the rate of development indicating early translation to routine clinical care. A key factor in their success will depend on rigorous quality control and on ensuring that the quantitative measurements are robust and reproducible.
