Metastatic breast cancer is defined as invasive breast cancer that has spread beyond the breast. According to stagewise classification, it is known as stage IV breast cancer, secondary breast cancer, or advanced breast cancer.
When this cancer spreads to other parts of the body, it is called breast cancer metastasis.
It is but natural for a woman diagnosed with breast cancer to ask her doctor that one question: Has it spread? If her doctor answers in the affirmative, she knows she has very little time. Her life and the world then change forever.
Today, most women with breast cancer are diagnosed early before metastasis occurs. However, some women are first diagnosed after they have already developed metastatic breast cancer. According to cancer.net, about six percent of women have metastatic breast cancer when they are first diagnosed.
How does breast cancer spread?
In breast cancer metastasis, cancer cells break away from the primary breast cancer tumor and travel to other parts of the body through the blood vessels or the lymphatic system. They get lodged there and form a new cancer deposit.
There are several ways breast cancer can spread in the body.
- Direct invasion happens when the cancer cells spread to the neighboring breast tissue. The cancer cells take root and begin to grow in this new area.
- In the lymphatic spread, the cancer cells travel to the neighboring lymph nodes in the axilla and above the clavicle bone, and through the lymphatic circulatory system, they settle in different parts of the body.
- Hematogenous spread occurs through the blood vessels. The cancer cells travel through the blood circulation system and take root in far-off areas and organs in the body.
The newly formed cancer deposit is called secondary breast cancer and the original breast cancer tumor is called primary breast cancer.
The secondary metastatic tumor that develops in a different part of the body is made up of breast cancer cells. For example, if breast cancer spreads to the bone, the metastatic tumor in the bone will have breast cancer cells, not bone cells.
Where can breast cancer spread?
The most common places of recurrence and breast cancer metastases are:
- Locally. Can recur in the same place or the underlying tissue where the operated breast used to be.
- Regional lymph nodes that can be invaded are the ones in the axilla (armpit), above and below the collarbone, and the ones behind the breastbone.
- Bones,
- Liver,
- Lungs, and
- Brain.
Among these, the most common site of breast cancer metastasis is the bone.
Symptoms
Symptoms of breast cancer metastasis will vary depending on where the breast cancer has metastasized. However, you will see certain general symptoms such as weakness, fatigue, malaise, loss of appetite, and loss of weight. Specific symptoms at times can arise very late after metastatic cancer has significantly progressed.
Symptoms of local recurrence in the same breast site
- Change in the size and shape of the breast
- A lump or thickening in the breast or axilla that persists
- A dimpled, scaly, puckered, or inflamed reddish skin over the breast or nipple
- Clear or blood-tinged discharge from the nipple
Symptoms of breast cancer metastasis to bone
As mentioned above, about 90% of deaths in women with breast cancer are due to metastasis and 70% of these deaths occur due to bone metastasis. The bones most commonly affected bones are the spine, ribs, skull, pelvis, and the long bones of the arms and the legs. Symptoms include:
- Severe and increasing bone pain
- Pathological fractures
- Erythema over the affected bone (redness of the skin)
- Swelling
- Hypercalcemia ( increased blood calcium levels)
- Spinal cord compression is when there is breast cancer metastasis to the spine.
Symptoms of breast cancer metastasis to the brain
About 10% of breast cancer metastasis occurs in the brain. Symptoms include:
- Persistent and progressive headache
- Changes in vision
- Convulsions
- Nausea or vomiting
- Behavioral changes
- Vertigo
- Increased intracranial pressure
- Ataxia or lack of coordinated muscle movements
Symptoms of breast cancer metastasis to liver
- Jaundice
- Pain in the abdomen
- Loss of appetite
- Nausea and vomiting
- Blood pathology will show elevated levels of liver enzymes SGOT and SGPT.
Symptoms of breast cancer metastasis to lungs
- Chest pain
- Shortness of breath
- Chronic cough
- Blood in the sputum
- Chest X-ray will show the metastasis
Statistics
The statistics given below are those of 2007.
- An estimated 155,000 women are living in the U.S. with breast cancer metastasis. By 2011, this figure is expected to rise to 162,000.
- 20% to 30% of women diagnosed with breast cancer develop breast cancer metastasis.
- Only 27% of the patients who have breast cancer metastasis survive for 5 years.
- Every year since the year 2000, about 40,000 Americans die of breast cancer metastasis.
- That translates to one American death every 14 minutes due to metastatic breast cancer.
- In 2021, in the United States, an estimated 284,200 people (281,550 women and 2,650 men) will be diagnosed with metastatic breast cancer.
- It is estimated that 44,130 people (43,600 women and 530 men) will die from breast cancer this year. Most of these deaths will be due to metastatic breast cancer.
Diagnostic tests
History and symptoms act as pointers to the likely site of metastasis and the suspected organs are subjected to the following tests.
- Bone scan
- Chest X-ray
- CAT scan
- MRI
- A combination of PET and CT may be required in certain cases.
- Blood tumor marker tests measure the markers in the blood. CA 15-3 and CEA (carcinoembryonic antigen). These markers are elevated in metastatic breast cancer.
The doctor orders imaging tests
- CAT scans and MRIs help to study the lungs, liver, pelvis, spine, brain, and extremities. They can help your doctor visualize these different parts of your body all at once.
- To look more closely at doubtful areas that might be cancer.
- To learn how much cancer might have spread.
- To determine if treatment is working.
- To look for possible signs of cancer recurrence
Treatments for breast cancer metastasis
There is no cure for metastatic breast cancer. Treatments do not cure this disease but aim at alleviating the symptoms and maintaining the quality of life. In other words, this treatment is only palliative (to treat the symptoms).
Hormone therapy
Hormone therapy or endocrine therapy aims at blocking the action of estrogen to curtail the growth of this hormone-dependent cancer, especially in metastasis to the bone. This is done in the following ways.
- Surgical removal of the ovaries
- Medications such as tamoxifen or toremifene prevent the ovaries from using estrogen
- Gonadotropin-releasing hormone antagonists medications are given to prevent the ovaries from producing estrogen.
Indications for this therapy are prior confirmation that the breast tumor is estrogen and/or progesterone dependent for its growth. This is confirmed by the diagnostic tests done when the cancer of the breast was confirmed.
Contraindications for this therapy include liver metastasis, significant lung involvement, rapid progression of the disease, and where symptomatic treatment is required for severe symptoms.
Radiation therapy
Radiation therapy makes use of penetrating high-energy beams to kill and curtail the growth of cancer cells. Commonly, the following metastases are treated with this therapy
- Spinal cord compression
- Liver metastases
- Brain metastases
- Bone metastases
Chemotherapy
Chemotherapy is an effective way to treat breast cancer metastasis. A combination of chemotherapeutic drugs is often used. Chemo aims at stopping or slowing the growth of cancer cells. Chemo treatments are given at intervals of 21 to 28 days to allow the patient to recover from the side effects.
Indications for chemotherapy:
- When hormone therapy becomes ineffective
- When hormone therapy cannot be given as in hormone receptor-negative metastatic breast cancer
- Any other metastatic breast cancer that is rapidly progressing
- Abraxane and Eribulin are two examples of chemotherapeutic agents used.
Surgery
Surgery is indicated in certain conditions to remove the primary tumor or a metastatic site to reduce the symptoms. If the initial cancer was treated with lumpectomy and radiation, the local recurrence is treated with mastectomy followed by the suitable treatments mentioned above.
Radiopharmaceutical treatment
Radiopharmaceutical treatment consists of injection of drugs Metastrone or Quadramet by intravenous route. It is administered by nuclear medical scientists in a nuclear medicine facility. One injection can give relief from bone pain for weeks or months.
Prognosis and survival rate
The situation for secondary breast cancer is not so hopeless now. In 1970, only 10% of women survived for 5 years after being diagnosed with metastatic breast cancer. Today, researchers put that figure at 40%. It is being approached as a chronic condition and is managed as such.
There are two types of breast cancer metastasis:
- In the first type, the breast cancer cells spread to the axillary (armpit) lymph nodes. This stage is still curable with proper surgery and systemic treatments. All of the cancer can be removed and a good prognosis can be offered to the patient.
- The second type is when cancer has spread beyond the axillary lymph nodes to distant organs mainly to the bones, liver, brain, or lungs. Here, the survival can be for a few years but premature death is at last inevitable.
- About 90% of deaths in women with breast cancer are due to metastasis and 70% of these deaths occur due to bone metastasis.