Assessing Treatment Response of Breast Cancer Using Multimodal Functional Imaging

Patients with large primary operable breast cancers are offered chemotherapy prior to surgery to shrink the tumour and enable breast conserving surgery. Conventional assessment of response to chemotherapy relies on a change in tumour size which does not always correlate with the change in amount of viable tumour. Newer techniques such as functional MRI, microbubble and optoacoustic ultrasound offer the potential to detect responses to chemotherapy by evaluating functional changes in tumour vascularity and oxygenation. Neither modality utilises ionising radiation.

Although MRI is widely used for detecting breast cancer, its ability in assessing functional responses to chemotherapy prior to surgery has not been fully exploited. Dynamic contrast enhanced (DCE) MRI has a sensitivity around 90% and provides quantitative measurements of blood volume and flow. Other functional techniques detect variation in tissue oxygenation: this is called the blood oxygen level-dependent (BOLD) mechanism. The BOLD technique uses a special magnetic resonance (MR) sequence called T2* to measure the weakly magnetic effect of deoxygenated haemoglobin. The investigators wish to develop and validate T2* measurements which relate to oxygenation of a tumour. The investigators also want to validate other MR sequences including diffusion weighted (DW) MRI, which quantifies microcirculation of blood in the capillary network and the diffusion of water within tissues.

Microbubble ultrasound is an established technique that utilises an intravenous contrast agent comprising tiny microbubbles of gas that can increase the reflectivity of blood and enhance spectral and colour Doppler signals obtained from routine ultrasound imaging. Optoacoustic imaging is new technique where the output signal depends on the oxygenation of the tissues under study. It utilises a light signal input and measures ultrasound signal output.

The investigators want to correlate our imaging findings with histopathology after surgical resection of the tumour.