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

MRI Scans May Predict A Woman’s Future Risk Of Developing Breast Cancer

Research by Dontchos et al published in Radiology suggests that MRI of the breast may predict a woman’s future risk of developing breast cancer.  They looked whether qualitative magnetic resonance imaging (MRI) assessments of background parenchymal enhancement (BPE), amount of fibroglandular tissue (FGT), and mammographic density are associated with risk of developing breast cancer in women who are at high risk.

They reviewed all screening breast MRI studies obtained from January 2006 to December 2011 in women aged 18 years or older and at high risk for but without a history of breast cancer. Women in whom breast cancer was diagnosed after index MR imaging comprised the cancer cohort, and one-to-one matching (age and BRCA status) of each woman with breast cancer to a control subject was performed by using MR images obtained in women who did not develop breast cancer with follow-up time maximized. Amount of BPE, BPE pattern (peripheral vs central), amount of FGT at MR imaging, and mammographic density were assessed on index images.

Twenty-three women at high risk (mean age, 47 years ± 10 [standard deviation]; six women had BRCA mutations with no history of breast cancer underwent screening breast MR imaging; in these women, a diagnosis of breast cancer (invasive, n = 12; in situ, n = 11) was made during the follow-up interval. Women with mild, moderate, or marked BPE were nine times more likely to receive a diagnosis of breast cancer during the follow-up interval than were those with minimal BPE. BPE pattern, MR amount of FGT on MRI, and mammographic density were not significantly different between the cohorts.

Greater background parenchymal enhancement (BPE) was associated with a higher probability of developing breast cancer in women at high risk for cancer and warrants further study.

3-minute MRI of the Breast for Cancer Screening

Kuhl et al in their JCO article report on the suitability of a fast MRI of breast cancer for screening.  Their protocol consisted of one pre-contrast and one post-contrast sequences their derived images [FAST] and maximum-intensity projection [MIP] images.

They conducted a prospective observational study in 443 women who were at mildly to moderately increased risk for breast cancer who underwent 606 screening MRIs. Eligible women had normal or benign digital mammograms and, for those with heterogeneously dense or extremely dense breasts (n = 427), normal or benign ultrasounds. Breast radiologists with expertise in MRI reviewed the MIP image first to search for significant enhancement and then reviewed the complete study that consisted of MIP and FAST images and optionally their non-subtracted source images and characterized the enhancement in order to establish a diagnosis. Only thereafter was the regular full diagnostic protocol study was analyzed.

MRI acquisition time for complete diagnostic protocol was 17 minutes, versus 3 minutes for the abbreviated protocol (AP). Average time to read the single MIP and complete AP was 2.8 and 28 seconds, respectively. Eleven breast cancers (four ductal carcinomas in situ and seven invasive cancers; all T1N0 intermediate or high grade) were diagnosed, for an additional cancer yield of 18.2 per 1,000. MIP readings were positive in 10 (90.9%) of 11 cancers and allowed establishment of the absence of breast cancer, with a negative predictive value (NPV) of 99.8% (418 of 419). Interpretation of the study using the abbreviated protocol, as with the full diagnostic protocol(FDP), allowed diagnosis of all cancers (11 [100%] of 11). Specificity and positive predictive value (PPV) of AP versus FDP were equivalent (94.3% v 93.9% and 24.4% v 23.4%, respectively).

The authors conclude that the 3 minutes abbreviated protocol and a MIP image are sufficient for an expert radiologist to establish in 3 seconds the absence of breast cancer, with an NPV of 99.8%. With a reading time < 30 seconds for the complete AP, diagnostic accuracy was equivalent to that of the FDP and resulted in an additional cancer yield of 18.2 per 1,000.

MRI and Mammography Combined are Effective in Detecting Breast Cancer in Women at High Risk

Chiarelli et al in their JCO article report on Ontario’s Breast Screening Program of women age 30 to 69 years at high risk for breast cancer with annual magnetic resonance imaging (MRI) and digital mammography.

The study cohort consisted of 2,359 women. The following criteria were used to determine eligibility: known BRCA1, BRCA2 mutation, or other gene predisposing to a markedly increased risk of breast cancer, untested first-degree relative of a gene mutation carrier, family history consistent with hereditary breast cancer syndrome and estimated personal lifetime breast cancer risk of 25% or higher, or radiation therapy to the chest before age 30 years.

Digital mammograms were performed with standard craniocaudal and mediolateral oblique projections.  The minimum MRI standards were 1.5 Tesla units, gadolinium injection (0.1 to 0.2 mmol/kg) and a dedicated breast coil. Both breasts were imaged in axial and sagittal planes.  Most of the eligible women (90.7%) had their MRI within a month from their mammograms.  Of the 2,359 eligible women 2,290 were screened.  Of the women screened 2,157 had an MRI and were included in the study as women who had only a mammogram were excluded.

The recall rate of 15% was significantly higher among women who had abnormal MRI alone compared with 6.4% when mammogram alone was used.  Of the 35 breast cancers detected (16.3 per 1,000), none were detected by mammography alone, while 23 (65.7%) were detected by MRI alone (10.7 per 1,000), and 25 (71%) were detected among women who were known gene mutation carriers (30.8 per 1,000). The positive predictive value of 12.4% for detection was highest when findings from mammogram and MRI were combined.  Overall, the cancer detection rate was significantly higher for invasive cancers (12.6 per 1,000) compared with DCIS (3.7 per 1,000). Cancer detection rates were higher among women age 50 years (23.3 per 1,000) compared with women younger than age 50 years (13.3 per 1,000) and significantly higher among those who were known gene mutation carriers (30.8 per 1,000) compared with those with a family history plus an estimated lifetime cancer risk of 25% (6.9 per 1,000).

The authors conclude that screening with annual MRI combined with mammography is effective and could be implemented into an organized breast screening program for women at high risk for breast cancer as mammograms alone failed to detect early breast cancers. 

An editorial by Dr. Wendie Berg with comments on this topic was published by the Journal of Clinical Oncology.