The early data were presented at the 2011 Cancer Therapy & Research Center-American Association for Cancer Research (CTRC-AACR) San Antonio (TX, USA) Breast Cancer Symposium, held December 6-10, 2011. “Breast cancers are heterogeneous, and different subtypes of breast cancer will respond differently to therapy,” said Sana Parsian, MD, a research assistant in the department of radiology at the University of Washington (Seattle, USA). “Every patient with breast cancer must undergo biopsy to be evaluated for the type of breast cancer they have. Based on that, adjuvant medical therapies are prescribed for them.”
Dr. Parsian and her colleagues theorized that some quantitative MRI applications, such as diffusion-weighted MRI (DWI) and dynamic contrast-enhanced (DCE) MRI, would correlate with histopathological markers by enabling the researchers to measure the tumor’s vascularity and cellularity.
In DWI, the diffusion of fluids along a field gradient reduces the MRI signal, so it can determine cellularity of the tumor by measuring the degree of water mobility. DCE enables viewers to see more information about tumor vascularity. A malignant cell cluster requires a blood supply to grow, and those vascular alterations cause tumors to appear differently on DCE compared with normal tissue, according Dr. Parsian. The enhancement pattern seen on an MRI is known as kinetics.
The researchers evaluated correlations between DWI and DCE kinetics and histopathological markers of breast cancer determined from biopsy, such as estrogen receptor (ER), progesterone receptor, HER2, p53, and the ki67 proliferation marker, in 41 invasive tumors among 36 patients. They found statistically significant correlations between MRI measures and all markers, except ER, which was only slightly associated with one of the DCE measures. Each of the DCE kinetics parameters significantly discriminated grade III tumors from grades I, II, and luminal A from luminal B and basal-like intrinsic subtypes. “When we looked at these measures, we realized there was a correlation with biomarkers,” Dr. Parsian said.
Even though these are early findings, Dr. Parsian hopes that MRI will provide valuable noninvasive data about tumor biology for choosing and guiding targeted therapies. Dr. Parsian noted that larger prospective studies are needed to validate these results and that MRI may complement biopsy to sample the whole tumor and reflect tumor heterogeneity. “I think the final goal of radiology is to get more information while doing the least amount of intervention possible for the patient,” she concluded. “It would be great if we could improve our understanding of breast cancer biology and predict response to different therapies with imaging. Our study suggests MRI may play a valuable role in this process.”
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