Brain Metastases: A Growing Area of Concern in Breast Cancer
Aashna Chudgar and Netra Ramanatham, Lynbrook High School, San Jose, California, USA
Breast cancer is one of the most common cancers that metastasize, or spread to other areas of the body. Metastasis occurs in 10-30% of breast cancer patients. One of the most common areas of breast cancer metastasis is the brain. With the breast cancer rate increased to 1 in 8 women in the US in 2022, the concern of brain metastasis from breast cancer moves closer to the forefront of global health issues. Many cancer experts are working to develop treatments, and ongoing research on combining treatments shows immense promise.
Approximately 1 in 8 women in the United States are diagnosed with breast cancer every year, giving it not only the reputation of one of the most pressing women’s health issues in history, but also the leading cancer in female populations globally (American Cancer Society, n.d.). At the beginning of 2022, the annual estimate of new breast cancer diagnoses was 287,580 for women, as well as an additional 2,710 in men (National Breast Cancer Coalition, 2022). Breast cancer is by no means an exception to the ever prevalent inequity that exists in global healthcare. In 2020, there were 685,000 deaths worldwide due to breast cancer, with a disproportionate amount of these deaths being concentrated in countries undergoing economic transition (Arnold, 2022).
Breast cancer is one of the most likely cancers to metastasize to the brain, which occurs in 10-16% of breast cancer patients (Leone, 2015). Brain metastases is when cancerous cells spread to the brain, typically the cerebellum, through the bloodstream, and can cause memory loss, sudden behavioral changes, and vision and hearing loss (Bettegowda, n.d.). Since brain metastases can cause severe neurological damage, patients with breast cancer that metastasizes have a higher chance of mortality and side effects much worse than that of the average case of breast cancer.
Breast cancer is also not a singular disease, but rather subtypes of diseases that can have varying ability to spread throughout the body depending on the receptors present in the breast tissue. Human Epidermal Growth Factor Receptor 2 (HER2) positive breast cancer is one of the more aggressive subtypes and is characterized by the presence of the HER2 cellular receptor in breast tissue. While many different receptors activated by estrogen and progesterone respectively, such as estrogen receptor and progesterone receptor, can induce rapid cell growth, HER2 has a reaction that involves many cell signaling pathways and therefore generates a larger response that can lead to brain metastases (Tareen, 2020).
The two main forms of current treatments for brain metastases, especially those for breast cancer, include systemic (chemotherapy, therapeutic antibodies, tyrosine-kinase inhibitors) and local (surgery, radiotherapy) treatment (Bailleux, 2020).
Figure 1: Chemotherapy, being a chemically induced treatment, is administered to patients via IV (Stephen, 2022).
Chemotherapy, one of the most widely known forms of cancer treatment, uses chemicals that damages and breaks down the nucleus of dividing cancerous cells through circulating bloodstream. However, the chemicals can also damage hair follicles, which is why patients going through chemotherapy often face hair loss (cancerresearchuk.org, 2020). Radiation therapy, on the other hand, destroys the DNA of cancerous cells to break them down. The process to damage the DNA of cancerous cells and the eventual death of the cells is very slow and can take from days to weeks (cancer.gov, 2019). There are also various surgeries that are often performed as cancer treatments, either to remove an entire tumor, or to debulk it—remove some or most of a tumor to facilitate use of another treatment (cancer.net, 2021).
Use of combined methods, such as chemotherapy and radiotherapy before surgery, have been shown to reduce relapses in breast cancers from 6-13% to 5% (breastcancer.org, 2010). Another common combined method of treatment is, as mentioned above, use of surgery as a precursor to a further treatment, which is often radiotherapy in the case of brain metastases. This treatment has been shown to improve overall survival rates (Bailleux, 2020).
Cancer treatments have by and large improved exponentially in recent years. However, this growth is not even close to treating the disparities in healthcare between high- and middle- to low-income countries. In 2030, the difference in breast cancer deaths between developing and developed countries is predicted to be 5.24 million deaths. Cancers are one of the leading causes of death in people today, surpassing other global health concerns such as HIV/AIDS, tuberculosis, and malaria by a long shot (Moten, 2014). Lack of awareness for preventative care and early detection simply allows for the issue to continue unchecked and further contributes to growing mortality rates in disadvantaged communities lacking proper resources (de Souza, 2016).
Figure 2: Cancer deaths in developing countries account for around 60-65% of worldwide cancer deaths. These percentages are increasing year by year, and are approximated to account for over 70% of cancer deaths within 10 years (Moten, 2014).
With the promise shown by combining methods, further research efforts will continue to advance efficiency and accessibility of treatments for breast cancers metastasized to the brain. Because breast cancer, like most other cancers, is due to an acclimation of genes and exposure to radiation, there are not very many preventative measures that can be taken to avoid breast cancer, much less brain metastases. For this reason, the best way to prevent tumor metastases throughout the body is to receive regular breast cancer screening. This also makes the efficiency of treatments such as combined methods all the more necessary.
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