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Bone Metastasis

Metastatic breast cancer cells tend to spread to the bones more often than they do to other parts of the body. More than half of people who develop stage IV breast cancer have bone metastasis.
 

Metastatic breast cancer cells tend to spread to the bones more often than they do to other parts of the body. More than half of people who develop stage IV breast cancer have bone metastasis.

Although breast cancer can spread to any bone, the most common sites are the ribs, spine, pelvis, and long bones in the arms and legs.

 

Symptoms and diagnosis of bone metastasis

A sudden, noticeable new pain is the most common symptom of breast cancer that has spread to the bone. The pain may come and go at first but can become constant over time. It can be hard to tell the difference between bone metastasis pain and arthritis pain or exercise strain. If the pain feels just as bad or even worse when you rest or lie down, it can be a sign of a problem. It’s a good idea to see your doctor right away; if it is bone metastasis, prompt treatment can prevent a fracture down the road.

Complications of bone metastasis are called skeletal-related events (SREs) and can include the following:

  • sudden severe pain and the inability to move, which can be a sign of fracture

  • pain in the back or neck, numbness or weakness in an area of the body, or difficulty passing urine or having bowel movements — all possible signs of spine compression, which can happen when a fractured vertebra presses on the spinal cord nerves that control various bodily functions

  • fatigue, weakness, nausea, loss of appetite, or dehydration, which can indicate very high levels of calcium in the blood due to bone breakdown

To diagnose bone metastasis, your doctor usually orders one or more of the following imaging tests:

Your doctor also may order a blood test to check for high levels of calcium or alkaline phosphatase (ALP), another substance that can be elevated because of bone metastasis.

In some cases, doctors may need to perform a biopsy to confirm a metastatic breast cancer diagnosis. Using CT scans, a doctor can guide a small needle into the suspicious area and remove a sample of tissue to be examined in the lab.

 
 
 

Treatments for bone metastases

To understand how treatments for bone metastasis work, it can help to first understand how breast cancer cells behave in the bones.

A bone can function like a storage tank that traps and holds breast cancer cells. For some time, those cells may not cause any problems. Eventually, though, the cancer cells can hijack the normal, healthy process through which bone tissue regenerates itself.

Your bones are constantly breaking down and clearing away old cells and stimulating new cells to grow. Breast cancer cells in the bone can speed up the breakdown of normal bone tissue and weaken the bones. This is called osteolytic metastasis. Breast cancer cells also can overstimulate the production of new bone, leading to large, rigid growths. This is called osteoblastic metastasis.

It’s possible to have osteolytic metastasis, osteoblastic metastasis, or a combination of both. Treatment helps slow or stop these bone metastasis cycles to reduce the risk of what’s called a skeletal-related event (SRE).

Examples of SREs include:

  • bone fracture

  • spinal cord compression, a bone fracture that presses on the spinal cord

  • hypercalcemia of malignancy, or an excessive amount of calcium in the blood

It’s important to address any potential symptoms of bone metastases quickly. In addition to controlling the growth of the cancer, the goals of treatment for bone metastasis are to relieve pain, preserve function, and prevent SREs. Doctors can often stabilize bone metastases and help people manage it for long periods of time.

There are many treatment options for bone metastasis. Your doctor may recommend just one or a combination of approaches depending on your symptoms, how extensive the cancer in the bone is, and whether it has progressed enough to create a fracture risk.

As needed, your doctor may call in other specialists, such as a radiation oncologist or surgeon, to deliver treatments. Your doctor can advise you on which treatments make the most sense for your situation. Your choices may depend in part on what technologies and experts are available close to where you live.

Metastatic breast cancer in any part of the body is usually treated with systemic medicines, which treat cancer throughout the entire body. Chemotherapy, hormonal therapy, targeted therapies, and immunotherapy are all systemic medicines. For bone metastases, bone strengthening medicines are often used, as well. And local treatments that specifically target the bones, such as surgery or radiation, are sometimes recommended.

Chemotherapy to treat bone metastasis

Chemotherapy destroys or damages cancer cells as much as possible and, therefore, doctors recommend it as a treatment for metastatic breast cancer in any part of the body. Because chemotherapy medicines are systemic treatments — meaning they affect the entire body — doctors generally recommend chemotherapy if:

  • the cancer is growing despite other forms of treatment

  • there is a significant amount of cancer in organs such as the liver or lungs

  • the cancer is growing quickly

Doctors often combine chemotherapy with targeted therapies, which are medicines that target specific characteristics of cancer cells.

Each person’s chemotherapy treatment plan is different. But there are some general guidelines that doctors follow when using chemotherapy to treat metastatic breast cancer:

  • If you’ve had chemotherapy before, your doctor may recommend using only one chemotherapy medicine at a time to treat metastatic disease. This way you can get benefits with fewer possible side effects.

  • In general, doctors use most chemotherapy medicines to treat metastatic disease until side effects become a problem or the medicines stop being effective.

  • Some chemotherapy medicines seem to work better against cancer tumors when they are combined. Research has shown that combining treatments has contributed to a better overall prognosis for some metastatic cancers.

If breast cancer comes back after chemotherapy or doesn’t respond to chemotherapy medicines, you can try a different combination of medicines. There are many chemotherapy medicines, and if one medicine or combination of medicines doesn’t work, there is almost always something else you can try.

 
 
Hormonal therapy to treat hormone receptor-positive bone metastasis

Hormonal therapy medicines — also called endocrine therapy or anti-estrogen therapy — are used to help shrink or slow the growth of hormone receptor-positive metastatic breast cancer in any part of the body.  Hormonal therapy medicines include:

  • tamoxifen

  • Arimidex (chemical name: anastrozole)

  • Aromasin (chemical name: exemestane)

  • Femara (chemical name: letrozole)

  • Faslodex (chemical name: fulvestrant)

Hormonal therapy does not work on hormone receptor-negative breast cancer.

Hormonal therapy medicines treat hormone receptor-positive breast cancers in two ways:

  • by lowering the amount of the hormone estrogen in the body

  • by blocking the action of estrogen in the body

You usually take hormonal therapy to treat metastatic hormone receptor-positive breast cancer for as long as it works. If the cancer stops responding to one hormonal therapy medicine, your doctor will usually recommend a different hormonal therapy medicine.

 
 
Targeted therapies to treat bone metastasis

Targeted therapies are treatments that target specific characteristics of cancer cells, such as a protein that allows the cancer cells to grow in a rapid or abnormal way. Targeted therapies are generally less likely than chemotherapy to harm normal, healthy cells. Some targeted therapies are antibodies that work like the antibodies made naturally by our immune systems. Because of this, they are sometimes called immune-targeted therapies.

 
 
Immunotherapy to treat bone metastasis

Cancer immunotherapy medicines work by helping your immune system work harder or more efficiently to fight cancer cells.

Your immune system is made up of a number of organs, tissues, and cells that work together to protect you from foreign invaders that can cause disease. When a disease- or infection-causing agent, such as a bacterium, virus, or fungus, gets into your body, your immune system reacts and works to kill the invaders. This self-defense system works to keep you from getting sick.

Immunotherapy uses substances — either made naturally by your body or man-made in a lab — to boost the immune system to:

  • stop or slow cancer cell growth

  • stop cancer cells from spreading to other parts of the body

  • be better at killing cancer cells

 
 
Bone-strengthening medications for bone metastasis

Bone-strengthening medications are used to treat bone metastasis by:

  • relieving bone pain

  • lowering the risk of osteoporosis (weakened bones)

  • lowering the risk of spinal cord compression

  • lowering the risk of breaking a bone weakened by the tumor

  • lowering high levels of calcium in the blood

Medicines called osteoclast inhibitors are the most common bone-strengthening medication for bone metastasis.

Osteoclasts are bone cells that break down bone tissue. Osteoclast inhibitors interfere with the activity of osteoclasts. These medications can delay SREs in the bone (such as fractures or spinal cord compression) while making the bones stronger. The medications can work in different ways, but they have similar effects.

Xgeva (chemical name: denosumab) is given monthly as an injection (a shot) under the skin.

Zometa (chemical name: zoledronic acid) is a type of medicine known as a bisphosphonate. Zometa requires an intravenous infusion — which means it is delivered directly into your bloodstream through an IV or a port — every three months.

There are some differences between Xgeva and Zometa:

  • Effectiveness: Xgeva is slightly more effective than Zometa at reducing the risk of complications from bone metastasis.

  • Treatment timing and frequency: Xgeva can be given more quickly than Zometa since it’s a single injection, but it must be given once a month. Zometa infusion takes more time, but it can be given less frequently. Research on the timing and frequency of these medications is ongoing, so be sure to check with your doctor about how often you need to take them.

  • Cost: A generic version of Zometa is available, which may make a difference in terms of insurance coverage. If Zometa isn’t available, your doctor may prescribe another bisphosphonate called Aredia (chemical name: pamidronate).

Before starting any bone-targeted therapy, your doctor must make sure your levels of calcium and vitamin D aren’t too low. If so, your doctor may recommend supplements before you begin the medication or even during your bone-targeted therapy.

It’s important to know that Xgeva and Zometa are associated with a rare side effect called osteonecrosis of the jaw, in which the cells in the jawbone start to die. Doctors often advise stopping the medication at least one month before having any dental work, including deep cleanings, fillings, and root canals. About two months after a dental procedure, you can start taking the medication again. Even if you’re not having dental work, it’s a good idea to let your dentist know you’re taking one of these medicines in case you develop problems that need immediate attention.

Kidney problems are another rare side effect of bisphosphonates such as Zometa and Aredia. Your doctor may decide to follow your kidney function over time.

Radiation therapy for bone metastasis

Doctors recommend radiation therapy to treat spots of cancer within the bones that are causing pain. If given soon enough, radiation therapy also can prevent the risk of fracture. There are different types of radiation therapy for bone metastasis:

External beam radiation therapy

For many women, a single dose or several doses of external radiation therapy — delivered to the affected areas of the bone — is enough to provide pain relief. It’s fairly common to have a pain flare two or three days later, but it usually only lasts for about 24 hours. Your doctor may give you the steroid medicine dexamethasone to prevent a pain flare.

Stereotactic body radiation therapy (SBRT)

SBRT targets high doses of radiation to the areas of cancer while minimizing any exposure to nearby healthy tissue. SBRT can treat small- to moderate-size tumors, either as part of a single treatment or a few treatments over time. With SBRT, the areas of cancer are mapped first using imaging scans so the beams can be targeted with great precision. You’re more likely to hear SBRT described with brand names such as CyberKnife or GammaKnife. This technology is not available everywhere, so check with your doctor.

Radiopharmaceuticals

If you have many painful bone metastases in different areas, your doctor may recommend an internal form of radiation that travels throughout the entire body. Medicines called radiopharmaceuticals are injected into a vein. The medicine moves through the body and concentrates in areas of the bone where there is a lot of cell activity — old cells dying and new cells growing — as is the case when cancer is present. The radiation that’s given off destroys the cancer cells. Doctors may use a radiopharmaceutical such as strontium-89 (brand name: Mestastron), or samarium-153 (Quadramet). This treatment tends to work best if the bone metastases are osteoblastic, meaning that they have led to enlarged, rigid growths on the bone.

Ablation for bone metastasis

In certain situations and at certain cancer centers, some doctors may recommend ablation if pain from bone metastases comes back or worsens after radiation therapy. Ablation is a procedure doctors can use to destroy tumors with heat, cold, or electrical current.

Using imaging scans to map the locations of the cancerous areas before or during the procedure, a small needle or probe can then deliver the treatment directly to the tumor.
Examples include:

  • thermal ablation, which uses very high temperatures

  • cryoablation, which uses freezing cold temperatures

  • radiofrequency ablation, which uses high-frequency electrical currents

Another option is focused ultrasound, which does not use a probe but instead focuses ultrasound waves on the areas of cancer within the bone. This produces high temperatures that destroy the cancer cells.

All of these therapies have different risks and side effects. Your doctor can help you decide what’s best for your situation. In some cases, the treatment team can insert bone cement to strengthen and stabilize the bone after an ablation procedure.

Bone cement for bone metastasis

To stabilize the bone, treat a fracture due to metastasis, or reduce pain, doctors can inject bone cement directly into any areas weakened by breast cancer.

There are a few examples of this technique:

  • Vertebroplasty: Guided by CT imaging, the doctor injects bone cement into the spinal bone, or vertebra, through a very small incision.

  • Kyphoplasty: This procedure also treats the spinal bone, but the doctor first inserts a small balloon to create a cavity in the bone and then injects the cement.

  • Cementoplasty: This term refers to the above techniques performed in any other bone in the body besides the spine.

Surgery for bone metastasis

If your bone is so weakened by metastasis that it has fractured or is about to fracture, you may need to have surgery. These fractures do not heal in the same way that healthy bone would.

There are a couple of surgical options for bone metastasis:

  • Surgically placing a support into the bone: A surgeon can place a rod, pins, screws, plates, or other devices to make the bone (or bones) stable again. This can help relieve pain and restore function.

  • Surgery to remove a bone tumor: In rare cases, if you have just a single area of metastasis in one area of a bone, you have no other evidence of breast cancer in the body, and you’re generally in good health, your doctor may consider surgery to remove the single tumor to give you a better chance of having an extended period with no evidence of disease.

Doctors have different opinions on the usefulness of surgery for bone metastasis, so talk with your medical team to see what they recommend.

— Last updated on August 16, 2022, 7:41 PM