Breast cancer, originating in the breast tissue, can spread to other parts of the body, including the lungs. When breast cancer cells travel to the lungs, it is called secondary or metastatic breast cancer, also known as lung metastases. These cancer cells in the lung are still breast cancer cells, not a new lung cancer.
The Nature of Cancer Metastasis
Metastasis is the process by which cancer cells detach from a primary tumor and migrate to form new tumors in distant parts of the body. This spread is a complex, multi-step process; while millions of cancer cells may break away daily, most do not successfully form new tumors. Cancer cells travel through the body primarily via two systems: the bloodstream (hematogenous spread) or the lymphatic system (lymphatic spread). In hematogenous spread, cancer cells enter blood vessels and are carried through the circulatory system. Lymphatic spread involves cancer cells entering lymph vessels, traveling through lymph nodes, and potentially reaching the bloodstream.
How Breast Cancer Reaches the Lungs
Breast cancer cells commonly reach the lungs through the lymphatic system and the bloodstream. Cells can enter small lymph vessels near the primary breast tumor, travel to lymph nodes, and eventually enter the bloodstream. The bloodstream offers a direct route, transporting cells from the breast area through the circulatory system. The lungs are a common site for metastasis because blood from many parts of the body, including the breast, passes through them. This rich blood supply and the lungs’ close proximity to the breast increase the likelihood of cancer cells settling and forming new tumors.
Recognizing Lung Metastasis
Symptoms of breast cancer that has spread to the lungs vary, and some individuals may experience no symptoms, particularly in early stages. When symptoms occur, they often resemble common respiratory conditions. These include a persistent cough, shortness of breath (dyspnoea), and chest pain or tightness. Other signs may include wheezing, fatigue, loss of appetite, and unintentional weight loss. In some instances, individuals may cough up blood (hemoptysis). A build-up of fluid between the lung and chest wall, known as a pleural effusion, may also occur, leading to breathlessness.
Confirming the Diagnosis
Confirming lung metastasis from breast cancer typically involves a combination of imaging tests and a biopsy. Initial imaging may include chest X-rays for a basic view of the lungs. More detailed images come from Computed Tomography (CT) scans, which offer cross-sectional views and identify potential cancer location and size. Positron Emission Tomography (PET) scans are often used alongside CT scans (PET/CT) to detect cancer cell activity by highlighting areas where a radioactive sugar substance is absorbed. Magnetic Resonance Imaging (MRI) may also be used for detailed soft tissue imaging. A definitive diagnosis requires a biopsy of the lung tissue, such as a needle biopsy or bronchoscopy. This procedure allows pathologists to confirm breast cancer cells in the lung, distinguishing it from a new primary lung cancer.
Treatment Strategies
Treatment for breast cancer that has spread to the lungs focuses on controlling cancer growth, managing symptoms, and improving quality of life, as metastatic breast cancer is generally not curable. Treatment plans are individualized, considering the cancer’s characteristics, such as hormone receptor status and HER2 status, as well as prior treatments and the patient’s overall health.
Systemic therapies are the primary approach, targeting cancer cells throughout the body. These include:
Chemotherapy, which destroys rapidly dividing cancer cells.
Hormone therapy, used for hormone receptor-positive cancers to lower or block hormones that fuel cancer growth.
Targeted therapy drugs, which specifically block processes within cancer cells that aid their growth and spread.
Immunotherapy, which helps the body’s immune system recognize and attack cancer cells.
Local treatments like radiation therapy may be used in specific cases to manage symptoms, such as pain or airway obstruction, or to treat isolated lesions. Surgery is less common but may be considered to remove cancerous tissue in select situations or to address complications like fluid buildup.