Understanding metastatic breast cancer and how it spreads
Sredharan M, Consultant Surgical Oncology, Manipal Hospital, Goa
Breast cancer is the most common cancer affecting women worldwide. While early-stage breast cancer can often be treated successfully, metastatic breast cancer (MBC) represents a more complex challenge.
Also known as Stage IV breast cancer, MBC is when cancer cells break away from the original tumour from the breast and spread to other parts of the body. The common places where the cancer spreads are the bones, lungs, brain and liver. Although the cancer spreads, it is still classified and treated as breast cancer because the cells retain characteristics of breast cells. MBC may develop from an initial breast cancer diagnosis, or, in some cases, it can be the first diagnosis a patient receives, known as de novo metastatic breast cancer.
How Does Metastatic Breast Cancer Spread?
Cancer spreads through a process called metastasis, where cells from the primary tumour invade nearby tissues, enter the bloodstream or lymphatic system, and travel to distant organs through circulation. Once carried through circulation to a distant organ, the cancer cells lodge in the blood capillaries, where they start dividing and form small tumours called micro-metastases. These then gradually grow and produce symptoms.
Certain factors can influence the likelihood of breast cancer spreading, including the type of breast cancer, the stage at diagnosis, and importantly individual biological characteristics like hormone receptor status (such as oestrogen and progesterone receptors) and HER2 (human epidermal growth factor receptor 2) status. These characteristics not only affect how the cancer behaves but also play an essential role in determining treatment options.
Symptoms of Metastatic Breast Cancer
The symptoms of MBC vary depending on where the cancer has spread.
- Bone metastasis – pain, fractures, or spinal cord compression.
- Lung metastasis – breathing difficulties, persistent cough, or chest pain.
- Liver metastasis – abdominal pain, jaundice, or swelling.
- Brain metastasis – headaches, seizures, blurring or double vision or neurological changes.
Early detection of metastatic symptoms can be challenging, as they may resemble less severe conditions.
Treatment Options for Metastatic Breast Cancer
Although metastatic breast cancer currently has no cure, several treatment options can help manage symptoms, improve quality of life, and extend survival. The treatment plan is usually personalized based on factors like hormone receptor status, HER2 status, and where the cancer has spread.
- Hormone Therapy: For cancers that are hormone receptor-positive, hormone therapies like tamoxifen or aromatase inhibitors can slow or stop cancer growth by blocking the effects of oestrogen. These are one of the best tolerated treatment options for MBC.
- Targeted Therapy: Targeted therapies, such as HER2-targeted drugs (e.g., trastuzumab), focus on specific proteins involved in cancer growth. These treatments tend to have fewer side effects than chemotherapy and can be effective in controlling disease.
- Chemotherapy: Chemotherapy is often used when cancer has spread widely or when other therapies are not effective. Chemotherapy can reduce tumour size, relieve symptoms, and help control the spread.
- Immunotherapy: For some patients, especially those with triple-negative breast cancer, immunotherapy drugs may help the immune system recognize and fight cancer cells.
- Radiation Therapy and Surgery: Although less common, these localized treatments can relieve pain or other symptoms in specific areas affected by metastatic cancer.
Living with MBC can be emotionally and physically challenging. Support from healthcare providers, loved ones, and patient support groups can provide comfort and a sense of community. Although cure is rarely possible in MBC, the recent treatment advancements mean more people are living longer, fulfilling lives even after an MBC diagnosis. A combination of medical support, lifestyle adjustments, and emotional care can make a significant difference in the journey with metastatic breast cancer.
