Feature article

Imaging in Metastatic Breast Cancer

The American Cancer Society estimates that about 266,120 new cases of invasive breast cancer and 40,920 deaths will occur in the United States due to breast cancer this year alone. Women are surviving longer than they have before due to early detection and treatment of breast cancer. The quality of life for cancer patients has also improved because of imaging, such as MRI, allowing doctors to easily monitor treatment effectiveness. However, for the past 20 years, breast cancer has caused approximately 40,000 deaths per year.2 All 40,000 deaths each year are due to metastatic breast cancer and 84% of these deaths will be in women over the age of 50. 

Once the cancer has spread beyond the breast and nearby lymph nodes into other organs, it is called breast cancer with metastatic disease, stage IV, or metastatic breast cancer (MBC).2,3,4 Even though it has spread beyond the breast, it is still called breast cancer because that is the place of origin of the cancer and the type of cancer cells the tumors contain. MBC is not curable, and treatment aims only to shrink or weaken cancer, manage symptoms and side effects, and prevent spreading. Treatments will change based on how well they're working and if the cancer continues to spread. Some patients' cancer adapt to the treatment and cause the patients to change their regimen for the sake of effectiveness.

Oncologists measure metastasis and treatments using imaging techniques, such as PET/CT. Unfortunately, PET/CT requires ionized radiation to perform the exam. Since cancer patients frequently undergo radiation therapy, this causes significantly higher levels of radiation. However, MRI is emerging as a promising source for diagnosing and treating metastatic breast cancer through the use of whole body MRI, diffusion weighted MRI, and unique imaging agents and does not require radiation.

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Diagnosis and Treatment

The current monitoring standard for metastasis is whole body PET/CT scans. PET/CT is useful for the detection of tumor recurrence and lymph node involvement, meaning that doctors can use this test to monitor how cancer is responding to treatment and how prevalent it is in areas that have already been diagnosed with metastasis. However, PET/CT is not the best option for detecting newly developing tumors in distant metastasis. Diffusion-weighted MRI (DWMRI) has become an excellent contender for detecting and staging metastatic tumors.5 MRI has been shown to be more sensitive to distant metastasis through whole body procedures. It is also significantly better for bone marrow assessment, because it is more sensitive to cell density. If doctors were to use MRI instead of PET/CT, it would cut down on the radiation that cancer patients have to have and can often better detect spreading.

MRI can map out the tissue structures in the body and determine abnormalities that other imaging might miss. MR can identify tumors in brain tissue due to its ability to map white matter, for example. Currently, only small cell and non-small cell lung cancer patients are screened for brain metastasis.6 In the future, certain breast cancer patients may benefit from this screening as well due to the risk of cancer spreading to the brain. A retrospective study found that high risk breast cancer patients were found to have larger and more numerous brain metastases compared to the patients with non-small cell lung cancer. These women were more likely to have symptoms, such as seizures, and would then be imaged for brain metastasis. The treatment for women with breast cancer who had brain metastasis had similar recurrence and treatment-based outcomes as those with non-small cell lung cancer. Breast cancer patients had a higher percentage of total deaths and a lower time of survival. The higher mortality rate was likely because the breast cancer patients were diagnosed at later stages in the disease. Although breast cancer patients present with more symptoms and have more metastases, the NCCN still has no guidelines for brain screening for breast cancer.

Early detection and diagnosis helps to ensure that the patient is getting the appropriate treatment.7 A study conducted in India evaluated 99 patients with known breast cancer. The participants had no symptoms at the time of the whole body MRI exam. Forty-seven of the patients were found to be positive for metastasis while 52 were negative. After following the patients as the disease progressed, the study revealed that the MRI was accurate, and the patients with positive results did end up developing metastasis in their bones. The doctors who conducted the study urge others to use whole body MRI to monitor metastasis, because it uses strong magnets instead of potentially cancerous radiation and has a high rate of accuracy.

In addition to providing appropriate treatment, finding metastasis in the first steps will allow for better outcomes for surgeons, because there will be fewer lesions in a localized site. Efstathios Karathanasis and his team at Case Western Reserve University are altering how MRI identifies changes in the body and allowing detection to happen sooner.8 The imaging agent they developed, an iron oxide nanoparticle, targets a biomarker associated with early development of cancer metastasis. This agent allows radiologist to see changes in molecular, rather than anatomic, information and detect metastasis in its initial step. In the future, the iron oxide agent could potentially deliver anticancer drugs before a tumor even forms.

Metastatic breast cancer causes all death due to breast cancer, because it is not curable. Early stage cancers are able to be removed and treated, leading to remission. Doctors work tirelessly to monitor and halt the progress of cancer and metastasis and use imaging tools to determine the best course of action for each patient. Whole body MRI is emerging as a major tool for this process and often shows tumors in tissue that other imaging tests may not show. It is also more sensitive to distant metastases and could identify malignant tumors before patients present with symptoms or even before the new tumors have formed. MRI should be considered for monitoring the 266,120 patients who will develop breast cancer this year and, hopefully, prevent extend the lives of cancer patients.

References

1. "About and Key Statistics." American Cancer Society. 2016; Updated 1 February 2018. Web. 23 October 2018. <https://www.cancer.org/content/dam/CRC/PDF/Public/8577.00.pdf>.

2. "Understanding Metastatic Breast Cancer." MBCN.org. Web. 17 October 2018. <http://mbcn.org/what-is-metastatic-breast-cancer/>.

3. "Metastatic Breast Cancer." Breastcancer.org. Edited 16 October 2018. Web. 17 October 2018. <https://www.breastcancer.org/symptoms/types/recur_metast>.

4. "Metastasis." CancerCenter.com. Web. 22 October 2018. <https://www.cancercenter.com/terms/metastasis/>

5. Atul Kapoor, et al. "Is Whole Body-Diffusion MRI an Alternative to PET-CT! A review of Literature." clinicsinoncology.com. 9 May 2017. Web. 23 October 2018. <http://www.clinicsinoncology.com/pdfs_folder/cio-v2-id1285.pdf>.

6. Anicka Slachta. "Brain MRI could ID metastases in breast cancer patients, but guidelines don't recommend it." RadiologyBusiness.com. 21 May 2018. Web. 17 October 2018. <https://www.radiologybusiness.com/topics/policy/brain-mri-could-id-metastases-breast-cancer-patients-guidelines-dont-recommend-it>.

7. American College of Radiology/American Roentgen Ray Society. "Whole body MRI is highly accurate in the early detection of breast cancer metastases." ScienceDaily. 9 May 2010. Web. 22 October 2018. <www.sciencedaily.com/releases/2010/05/100506083436.htm>.

8. Efstathios Karathanasis. "Detecting Early Onset of Metastatic Disease Using MRI." itnonline.com. 15 May 2013. Web. 17 October 2018. <https://www.itnonline.com/article/detecting-early-onset-metastatic-disease-using-mri>.