Did you know that stage 4 breast cancer, also known as "de novo metastatic breast cancer", is only discovered in 6 to 10% of women? However, nearly 30% of early-stage breast cancer cases eventually progress to this stage.

Overview

Metastasis occurs when cancer cells spread from the initial tumour to other body parts.¹ 

Metastatic breast cancer is stage 4 breast cancer that has progressed to other parts of the body months or years after initial diagnosis and treatment. 

De novo metastatic breast cancer occurs when the initial diagnosis of the disease is metastatic. By the time the initial diagnosis of breast cancer is made, the cancer has already spread beyond the breast and into other parts of the body.²                                                                                                          

How does metastatic breast cancer develop?

When the abnormalities in genetic material cause changes in breast cells (a mutation) and they start to multiply uncontrollably, breast cancer develops. Clumps and nodules begin to appear after some time.

Cancer cells can spread throughout the body and beyond the initial tumour through the lymphatic system (a network of lymph nodes and vessels that removes waste cells, viruses, and bacteria) or the bloodstream. In most cases, the immune system eliminates them. However, if the cells settle in or multiply in other organs or tissues, metastatic tumours can form.

The majority of cases of breast cancer occur by chance; there is no known cause. Age, hormones, and a family history of breast cancer are the main risk factors. The probability that metastatic tumours have already developed depends on the primary tumour's characteristics. Additionally, it is higher if the initial tumour is discovered in its advanced stage.³

The majority of metastatic breast cancer is recurrent, meaning the cancer has returned after treatment and is affecting organs and tissue far from the original tumour. When treatment fails to eliminate all of the cancer cells, breast cancer typically returns. Tumours may shrink significantly due to treatment, sometimes to the point that tests can no longer detect them. While a cancerous tumour can be surgically removed, this may not always be possible. After treatment, some cancer cells may remain in the body, growing stronger over time. These cells begin to expand and multiply once more. Because the lymph nodes and blood vessels carry fluid throughout the body, breast cancer cells can easily relocate to new locations, forming new tumours.⁴

Symptoms of metastatic breast cancer

General symptoms

The following are typical signs of secondary breast cancer: ⁵

• Weariness (fatigue)  
• Challenges sleeping 
• Inexplicable weight loss 
• Appetite loss 
• Feeling ill 
• Experiencing pain

Location-specific symptoms

The symptoms of metastatic breast cancer vary depending on where the secondary tumour is found. 

Symptoms of secondary tumours that are common include:^5,6

• Bone: One possible symptom is severe new bone pain that progressively becomes continuous. Bone metastases can also result in fractures
• Brain: Headaches, nausea, facial numbness, memory issues, aberrant behaviour, and changes in speech, vision or balance are all possible symptoms
• Liver: Liver metastases rarely cause symptoms. However, pain on the right side of the abdomen, weakness, a lack of appetite, and yellowing of the eyes and skin are all possible symptoms
• Lungs: Lung pain, dyspnea, chronic coughing, recurrent chest infection, and a buildup of fluid between the lung and the chest wall (a pleural effusion) are all indicators of lung metastases

Diagnosis of metastatic breast cancer

If there are signs of metastatic breast cancer, the doctor may recommend:⁴

• Breast biopsy: This test removes tissue or, occasionally, fluid from the suspected area. The extracted cells are then examined under a microscope to determine whether breast cancer is present
• Blood tests: This includes a complete blood count and metabolic panel
• Bronchoscopy: A procedure that examines the inside of the lungs with a scope, if a suspicious area is detected
• Imaging scans: This includes bone scans, chest X-rays, CT scans, MRIs, PET scans and ultrasound scans
• Taps: These procedures drain fluid from symptomatic areas. For example, a pleural tap drains fluid from the lung area, while a spinal tap removes fluid from the spinal cord region

Treatment options for metastatic breast cancer

Stage IV cancers have spread beyond the breast and nearby lymph nodes to other parts of the body. Breast cancer commonly spreads to the bones, liver, and lungs. The brain and other organs may also be affected.

The primary treatments for women with stage IV breast cancer are systemic drug therapies. 

Hormonal therapy 

Hormone therapy targeted towards estrogen and progesterone can be effective against some types of breast cancer. The growth of breast cancer cells is aided by receptors that bind to estrogen and progesterone. Hormone or endocrine therapy involves treatments that prevent these hormones from binding to these receptors. These therapies either lower the amount of estrogen in the body or block its ability to bind to breast cancer cells. Chemotherapy may be administered before hormonal therapy in some cases. The specific treatments needed will be determined by the oncologist. Targeted therapy and hormonal therapy may be combined. If the initial treatment fails or becomes ineffective, the oncologist will be able to recommend an alternative hormonal therapy.^7,8

Chemotherapy 

Anticancer medications used in chemotherapy (chemo) are administered orally or intravenously (into the vein). These drugs travel through the bloodstream to reach and target cancer cells throughout most of the body.⁹

Targeted drug therapy 

Targeted drug therapy involves medicines that aim at specific proteins in cancer cells to hinder their growth and spread throughout the body. Unlike chemotherapy, these drugs have different side effects and can either kill cancer cells or slow them down. The use of monoclonal antibodies, a targeted drug therapy, can control cancer cells in multiple ways and boost the immune system. These drugs can be effective even when chemotherapy is not, and they can also enhance the effectiveness of other treatments. ¹⁰

Immunotherapy 

The use of medicines to boost a person's immune system to better recognise and destroy cancer cells is known as immunotherapy. To strengthen the immune response, immunotherapy typically targets specific immune system proteins. The adverse effects of these medications differ from those of chemotherapy. ¹¹

Radiation therapy 

Another cancer treatment is radiation. It does as little damage to healthy cells as possible while destroying cancer cells in the area where radiotherapy is administered.

Secondary breast cancer can be treated with radiotherapy. The term for this is palliative radiotherapy. In cases where breast cancer has spread to the bones, skin, or brain, it is used to alleviate pain and other symptoms.⁸

Surgery 

Breast surgery comes in a variety of forms and may be performed for a variety of reasons, depending on the circumstances. For instance, surgery can be performed to: ¹²

• Restore the breast to its original shape once the malignancy has been removed (breast reconstruction). 
• Treat advanced cancer symptoms. 
• Remove as much cancerous tissue as possible  (mastectomy or breast-conserving surgery).
• Carry out an axillary lymph node dissection or sentinel lymph node biopsy to determine whether the cancer has progressed to the lymph nodes beneath the arm.

Summary

Metastatic breast cancer, or stage 4 breast cancer, is the most advanced stage of the disease, marked by its spread to distant organs. While it affects a relatively small percentage of women initially, nearly 30% of early-stage breast cancer cases eventually progress to this stage. Despite the challenges, advancements in treatment, such as hormonal therapy, targeted drugs, chemotherapy, and immunotherapy, allow patients to manage symptoms and maintain a better quality of life. Though metastatic breast cancer is not curable, ongoing treatment aims to control its growth, reduce tumour size, and help patients live longer and more comfortable lives. With continued research and support, there is hope for improving outcomes and offering new, effective therapies.

FAQs

If I have metastatic breast cancer, what should I expect?

You will have regular follow-up appointments with your healthcare provider if you are receiving treatment. They will assess your health as a whole and inquire about any new symptoms or concerns you may have. They'll run tests to see if the treatment is working.

Can breast cancer with metastasis be avoided?

Unfortunately, breast cancer cannot be stopped from spreading. It is essential to keep in mind that you are not to blame for developing metastatic breast cancer. Because some cancerous cells survive treatment and spread through your bloodstream or lymphatic system, you may develop metastatic breast cancer.

What is the duration of treatment?

If you have undergone treatment for early-stage breast cancer, you might be acquainted with regimens that entail administering cancer medications over a certain duration. At the time, getting rid of cancer was the aim. With metastatic breast cancer,  the objectives are to lessen the size of newly formed tumours, stop the spread of cancer and assist you in managing your symptoms. This implies that your course of treatment could last forever.