Techniques under study for use in diagnosing breast cancer include magnetic resonance imaging (MRI), positron emission tomography (PET) and gene expression profiling. These tools may provide information about tumors that can be used to help guide treatment.
Magnetic resonance imaging (MRI)
There is a growing interest in magnetic resonance imaging (MRI) as a tool to detect and diagnose breast cancer. MRI uses magnetic fields to create high quality images that in some cases may be better than mammograms and ultrasound images. For more on MRI and breast cancer screening, see the Early Detection section. MRI may be useful in helping diagnose breast cancer in certain cases. For women with hard-to-find (occult) breast cancers first diagnosed by cancer in the lymph nodes or distant metastases, MRI may be helpful in finding the original tumor in the breast [26]. And, in some cases, MRI may be helpful in finding local recurrence, predicting response to chemotherapy and guiding needle biopsies. Other uses for MRI under study include distinguishing cancerous breast masses from benign ones.
An increasingly common, but controversial, use of MRI is as a tool to help decide which surgery would be best in women diagnosed with breast cancer. MRI can find small tumors in the breast that may be missed by a mammogram. For this reason, some health care providers use MRI to decide whether mastectomy would be a better option than lumpectomy if cancer is too widely spread throughout the breast. A major concern about using MRI in this way is that it's not clear if the small masses that an MRI finds would be better treated by mastectomy or lumpectomy plus radiation [26]. This means that many women may choose mastectomy over lumpectomy based on MRI results, even though lumpectomy would be an equally good option. Further research may help shed light on this issue. Until results from studies are available, you should talk to your health care provider if you have any questions about the benefits and risks of using MRI for planning treatment.
Positron emission tomography (PET)
Positron emission tomography (PET) is based on the idea that cancer cells absorb sugar more quickly than other cells do. This technique involves injecting a radioactive sugar into the body. Sugar will build up more in cancer cells and can be detected by the PET scanner. PET is now used to find distant metastases (cancer that has spread beyond the breast to other organs, such as the lungs, liver and bone). And, it is being studied for further use in breast cancer diagnosis. PET is under study as a tool for finding cancer that has spread to the lymph nodes in the armpit (axillary nodes). Early evidence, however, suggests that it cannot give a detailed enough image to make it a good tool for this task [27].
Gene expression profiling
Gene expression profiling is a tool that lets scientists study thousands of genes at one time. Studying which genes are active (expressed) and which are inactive in different types of tumor cells may help researchers to develop more targeted treatment. And, this tool may allow scientists to compare gene expression in treated versus untreated tumor cells to learn how certain treatments affect tumors. [28,29]
Although gene expression profiling could someday be used to help make treatment decisions, it is still mostly limited to the research setting. Scientists are working to address the technical limits of the process. At this time, the FDA has not approved gene expression profiling for clinical use.
Subtypes of breast cancer
There is a growing interest in learning how molecular and genetic differences among breast cancers relate to prognosis and treatment. Understanding these differences may improve our ability to predict how a person's cancer will respond to a certain treatment. One current theory divides breast cancer into four molecular/genetic subtypes: luminal A, luminal B, basal-like/triple negative and HER2/neu-positive. At this time, only HER2/neu status is used in treatment planning. The other subtypes are not yet used in clinical settings, but in the future, they may be useful in choosing treatments and developing new therapies. Learn more about the subtypes of breast cancer.
Circulating tumor cells
Many studies have shown that circulating tumor cells levels can help predict survival time for people diagnosed with metastatic breast cancer [30-33]. The more circulating tumor cells in the blood, the more advanced metastatic breast cancer is likely to be. More of these cells may also show a lack of response to treatment. At this time, circulating tumor cell testing is not routinely done in clinical practice. It is still not known how much more information these tests provide over standard tests and tumor markers in guiding the treatment of metastatic breast cancer [34]. However, there is a large, ongoing clinical trial to study how best to use circulating tumor cell test results to improve chemotherapy choices for metastatic breast cancer.
Early findings suggests that circulating tumor cells may also help predict disease-free survival time in women with early breast cancer [35,36].
Updated 10/26/09
