DWI-MRI Predicts Breast Cancer Response to Treatment

Diffusion-weighted MR images (DWI_MRI) acquired 12 weeks after the start of neoadjuvant chemotherapy for breast cancer may provide the best indication of how patients will respond to treatment, according to a study published in Radiology.

The researchers analyzed 242 participants who were randomized to receive 12 weekly doses of paclitaxel with four cycles of anthracycline.   The MRI protocol included, DWI imaging T2-weighted and contrast enhanced sequences.

  

The authors concluded that after 12 weeks of therapy, change in breast tumor apparent diffusion coefficient at MRI predicts complete pathologic response to neoadjuvant chemotherapy

Breast MRI Without Contrast Detects Cancer.

According to a study published in Radiology a radiomics technique that is based on diffusion weighted imaging with an adapted kurtosis model reduces false-positive results in both malignant and benign breast lesions when compared with x-ray mammography.

This institutional study included 222 women at two study sites (site 1: training set of 95 patients; mean age of 58.6 years; with 61 malignant and 34 benign lesions; and site 2: independent set of 127 patients; mean age, 58.2 years with 61 malignant with 66 benign lesions). 

Among all 222 patients, histopathology results confirmed malignant lesions in 122 women (55%); invasive ductal carcinoma was the most common finding, in 90 patients (74%). Benign lesions were found in the remaining 100 women (45%); fibrosis (21 patients, 21%) and fibroadenoma (20 patients, 20%) were the most common abnormalities.

All women presented with findings suspicious for cancer at x-ray mammography (BI-RADS 4 or 5) and an indication for biopsy. Before biopsy, diffusion-weighted MR imaging (b values, 0–1500 sec/mm²) was performed by using 1.5-T imagers from different MR imaging vendors. Lesions were segmented and voxel-based kurtosis fitting adapted to account for fat signal contamination was performed. Conventional interpretations of MR imaging were also assessed for comparison.

The kurtosis radiomics model reduced false-positive results from 66 to 20 (specificity 70.0% [46 of 66]) at the predefined sensitivity of greater than 98.0% [60 of 61] in the independent test set, with BI-RADS 4a and 4b lesions benefiting from the analysis (specificity 74.0%, [37 of 50]; 60.0% [nine of 15]) and BI-RADS 5 lesions showing no added benefit. The model significantly improved specificity compared with the median apparent diffusion coefficient (P < .001) and apparent kurtosis coefficient (P = .02) alone. Conventional reading of dynamic contrast material–enhanced MR imaging provided sensitivity of 91.8% (56 of 61) and a specificity of 74.2% (49 of 66). Accounting for fat signal intensity during fitting significantly improved the area under the curve of the model (P = .001).

 The authors concluded the radiomics model based on kurtosis diffusion-weighted imaging allowed for reliable differentiation between malignant and benign breast lesions.

Combined MRS and DWI could Predict Stroke's Outcome

Parsons etal in their article that appeared in Neurology¹ report on the prognostic value of the biochemical changes seen with proton MR spectroscopy (MRS) in patients with ischemic stroke.

Nineteen patients had 36 1H MRS studies, 13 of the patients acutely (mean, 11.1 hours), 10 patients sub-acutely (mean, 3.9 days), and 13 patients at outcome (mean, 82 days). Single-voxel, long-echo, timepoint-resolved spectroscopy was used to obtain lactate, n-acetylaspartate (NAA), choline, and creatine levels from the infarct core. Diffusion-weighted imaging (DWI) was used to identify regions of ischemia for 1H MRS voxel localization.  Outcome measures were final infarct volume and clinical assessment scales (Canadian Neurological Scale, Barthel Index, and Rankin Scale).

Acute lactate/choline ratio correlated more strongly with clinical outcome scores and final infarct size than acute DWI lesion volume or acute NAA/choline ratio. Combination of acute lactate/choline ratio and DWI lesion volume improved prediction of all outcome scores. The predictive effect of acute lactate/choline ratio was independent of acute DWI lesion volume (p < 0.001). In subacute and chronic infarction, both lactate/choline and NAA/choline ratios continued to correlate with outcome (p < 0.05). At the chronic stage, persistent lactate/choline ratio elevation strongly correlated with outcome measures (r = 0.71 to 0.87).

The authors concluded that lactate/choline ratio measured in the acute infarct core by 1H MRS improves the prediction of stroke outcome and provides prognostic information complementary to DWI.

1. Parsons M, Barber P, Yang G, Darby et al: Combined (1)H MR spectroscopy and diffusion-weighted MRI improves the prediction of stroke outcome. Neurology. 2000 Aug 22;55 (4):498-505