Predicting breast cancer response to chemotherapy using quantitative magnetic resonance (MR) imaging

Change in tumour volume may be a relatively late manifestation of chemotherapy response in patients with inoperable breast cancer. Recent studies suggest that quantifying water apparent diffusion coefficient (ADC), microvessel permeability (K^trans) or water to fat signal ratio (WFR), using magnetic resonance (MR) imaging or spectroscopy, may provide an early indication of ultimate treatment response.

Imaging and spectroscopy were carried out prior to chemotherapy (TP0) and shortly after the second (TP2) and final courses. ADC was measured using echo planar imaging (EPI) (maximum diffusion gradient weighting 680 s/mm²); K^trans was measured using dynamic T₁-weighted gradient echo imaging (13 s temporal resolution); WFR was measured using stimulated echo acquisition mode (STEAM) spectroscopy (TE 135 ms); tumour volume was measured using high resolution, three dimensional, post contrast, fat-suppressed images (manually traced regions of interest).

Preliminary results from five (of 35 recruited) women who have completed their chemotherapy course (standard regimen involving 5-fluorouracil, epirubicin and cyclophosphamide) demonstrated that all tumours responded. Both the TP2:TP0 MRI volume ratio and the corresponding K^trans ratio accurately predicted response in all five cases. The corresponding ADC and WFR ratios predicted response in three out of five and four out of five cases, suggesting that they may be less reliable indicators of final treatment efficacy. Results from 25 out of 35 women (course completed) will be presented.