Breast cancer can progress to an advanced stage known as metastasis. This occurs when cancer cells from the original tumor in the breast break away and travel to other parts of the body, forming new tumors. This process signifies that the cancer has spread beyond its initial site.
Understanding Breast Cancer Metastasis
Even if breast cancer cells are found in a different organ, such as the bones, it is still classified as metastatic breast cancer, not bone cancer. These cells retain the characteristics of breast cancer cells.
The spread of cancer cells involves several steps. Cancer cells first grow into or invade nearby healthy tissue. They then penetrate the walls of nearby lymph nodes or blood vessels, entering either the lymphatic system or the bloodstream. Once in these circulatory systems, the cancer cells can travel to other areas of the body, where they may invade new tissue and form new tumors. Sometimes, these cells can remain dormant for months or even years before growing and spreading again.
Common Sites of Spread and Associated Symptoms
Breast cancer most commonly spreads to the bones, lungs, liver, and brain.
Bone metastasis is the most frequent site of spread, often affecting the spine, ribs, pelvis, and long bones in the arms and legs. Symptoms include severe, progressive bone pain that may not improve with rest. There is also an increased risk of bone fractures from minimal trauma, and elevated calcium levels in the blood, which can lead to fatigue, nausea, and loss of appetite.
When breast cancer spreads to the lungs, symptoms may be subtle or absent. Common signs include a chronic cough, shortness of breath, and chest pain or discomfort. Difficulty catching one’s breath after physical exertion is another potential indicator.
Liver metastasis may also produce few symptoms initially. When symptoms do occur, they can include jaundice (yellowing of the skin and eyes), itching, abdominal pain (especially in the upper right side), loss of appetite, nausea, vomiting, unexplained weight loss, confusion, or drowsiness.
Brain metastasis is less common but can cause significant symptoms, particularly with aggressive breast cancer types like triple-negative and HER2-positive breast cancer. These symptoms can include persistent, worsening headaches, seizures, changes in vision or speech, nausea or vomiting, vertigo, changes in personality or behavior, or an inability to move certain parts of the body.
Detecting Metastatic Breast Cancer
Detecting metastatic breast cancer involves a combination of imaging techniques, biopsies, and blood tests to determine the extent and characteristics of the spread, guiding treatment decisions.
Imaging techniques identify metastatic tumors throughout the body. Computed tomography (CT) scans of the chest, abdomen, and pelvis can identify spread to organs. Bone scans detect bone metastases, while positron emission tomography (PET) scans reveal metabolically active cancer cells throughout the body. Magnetic resonance imaging (MRI) provides detailed images of the brain and other soft tissues. A combined PET/CT scan offers a more detailed view of cancer presence.
Biopsies are the definitive method for confirming metastasis. This procedure involves removing a small tissue sample from a suspicious area for microscopic examination by a pathologist. A needle biopsy, where a thin needle is inserted into the suspected tumor area, is a common method.
The biopsy also provides information about the specific characteristics of the metastatic cells, such as their hormone receptor status (estrogen and progesterone receptors) and HER2 status. This information helps determine which treatments, such as hormone therapy or HER2-targeted drugs, might be most effective. A repeat biopsy may be performed if the metastatic cancer is a recurrence, to check if the hormone and HER2 status has changed from the original diagnosis.
Blood tests offer clues about cancer spread and a patient’s overall health, though they are not definitive on their own. A complete blood count (CBC) assesses bone marrow function, while tests for minerals and enzymes, such as liver function tests, can indicate issues in organs like the liver. Tumor markers, such as CA 27.29, CA-15-3, and CEA, measure specific proteins that may be elevated in the presence of cancer, potentially indicating disease growth or treatment response. Circulating tumor cells (CTCs) can also be measured through blood tests, as they are often present in people with metastatic cancer.
Treatment Strategies for Metastatic Breast Cancer
Treatment for metastatic breast cancer is systemic, affecting the entire body. It aims to control the disease, manage symptoms, and enhance quality of life. The approach often involves a combination of different therapies tailored to the individual’s cancer characteristics.
Chemotherapy uses drugs to kill fast-growing cancer cells throughout the body. Hormone therapy, also known as endocrine therapy, targets hormone receptor-positive breast cancers by blocking hormones like estrogen and progesterone that can fuel cancer growth. Targeted therapies work by specifically attacking certain molecules or pathways involved in cancer cell growth and survival. Examples include HER2-targeted drugs for HER2-positive breast cancer, and CDK4/6 inhibitors for hormone receptor-positive, HER2-negative breast cancer. Immunotherapy, a newer approach, helps the body’s immune system recognize and fight cancer cells.
Local treatments may be used to manage symptoms or address specific complications. Radiation therapy uses high-energy rays to shrink tumors, relieve pain, prevent fractures, or manage symptoms in other affected areas. Surgery may also be an option in certain situations, such as to remove isolated metastases or address complications like a fractured bone. These local treatments are generally aimed at improving comfort and function rather than curing the widespread disease.
Outlook and Management of Metastatic Breast Cancer
While metastatic breast cancer is generally not considered curable, advancements in treatment have made it a manageable chronic illness for many individuals. The focus of management shifts towards controlling the disease, alleviating symptoms, and maintaining a good quality of life.
Ongoing monitoring involves periodic imaging scans and blood tests to assess the cancer’s response to treatment and detect any changes. Symptom management and supportive care are also central to the treatment plan, addressing pain, fatigue, nausea, and other side effects, often with the help of palliative care specialists.
Participation in clinical trials offers access to new and experimental treatments that are not yet widely available. These trials contribute to the development of future standard therapies and provide patients with additional options. A multidisciplinary care team, including oncologists, radiologists, pathologists, surgeons, and supportive care providers, works together to develop and adjust the treatment plan, ensuring comprehensive and individualized care.