Bone Metastases: When Cancer Spreads to the Bones
Cancer that has started in one place can spread to and invade other parts of the body.
This spread is called metastasis. If a tumor spreads to the bone, it is called bone
Cancer cells that have spread to the bone can damage the bone and cause symptoms.
Different treatments are available to control the symptoms and the spread of bone
metastases. To better understand what happens in metastasis, it helps to understand
the anatomy of the bones.
Bone is a type of connective tissue made up mostly of minerals, such as calcium and
phosphate, and a type of protein called collagen. The outer layer of bone is called
the cortex. The spongy center of bone is called bone marrow.
Bone is alive and always repairing and renewing itself through a process called remodeling.
Two kinds of cells help with this process:
Osteoblasts are cells that build new bone.
Osteoclasts are cells that break down, or reabsorb, old bone.
Here are some of the things bones do:
The skeleton gives structural support.
Bones store and release minerals, such as calcium that the body needs to work properly.
Bone marrow makes and stores blood cells. These include red blood cells, white blood
cells, and platelets. Red blood cells bring oxygen to the rest of the body. White
blood cells fight infections. Platelets help the blood clot.
When cancer cells invade the bone, any or all of these bone functions may be affected.
How cancer spreads to the bone
When cells break away from a cancer tumor, they can move through the bloodstream or
lymph vessels to other parts of the body. Cancer cells can settle in an organ at a
distant location and start a new tumor. The original tumor that cells break away from
is called the primary tumor. The new tumor that forms is called the secondary tumor.
Secondary tumors in the bone are called bone metastases.
Different types of cancer tend to spread to certain sites in the body. For example,
many types of cancer commonly spread to the bone. The bone is a common site of metastasis
for these cancers:
What are bone metastases?
Bone metastases are not the same as cancer that starts in the bone. Cancer that starts
in the bone is called primary bone cancer. There are different types of primary bone
cancers, such as osteosarcoma.
A tumor that has metastasized to bone is not made of bone cells. Bone metastases are
made up of abnormal cancer cells that started from the original tumor site. For example,
lung cancer that spreads to the bone is made of lung cancer cells. In this case, bone
metastasis would be called metastatic lung cancer. In adults, metastatic bone cancer
is much more common than primary bone cancer.
Cancer cells that spread to the bone often stay in these places:
Cancer cells that spread from tumors in other parts of the body can form two main
types of bone tumors:
The tumor may eat away areas of bone. This creates holes called osteolytic lesions.
This can make bones fragile and weak. So the bones can break or fracture easily. These
areas may be painful.
The tumor may cause the bone to form and build up abnormally. These areas of new bone
are called osteosclerotic or osteoblastic lesions. These are hard, but they're weak
and unstable. They may break or collapse. They can also be painful.
Symptoms of bone metastases
Bone metastases can cause the following symptoms:
Pain is the most common symptom of bone metastasis. It's often the first symptom you
notice. At first, the pain may come and go. It is usually worse at night or with
bed rest. Over time, the pain may become severe. Still, not all pain means metastasis. Your
healthcare provider can help tell the difference between pain from metastasis and
aches and pains from other cuases.
Bone metastasis can weaken bones. This puts your bones at risk for breaking. In some
cases, a break (fracture) is the first sign of bone metastasis. The most common sites
where bones may break are the long bones of the arms and legs, and the bones of the
spine. For instance, sudden pain in the middle of your back may mean that a bone is
breaking or collapsing.
Numbness or weakness in the legs, trouble urinating or having a bowel movement, or
numbness in the belly are all signs that the spinal cord may be compressed. When cancer
metastasizes to the spine, it can squeeze or compress the spinal cord. The pressure
on the spinal cord may cause these symptoms, as well as back pain. If you have these
symptoms, you should tell a healthcare provider right away. If untreated, it can cause
Loss of appetite, nausea, thirst, constipation, tiredness, or confusion
These are all signs that you may have high levels of calcium in your blood. Bone metastases
can cause a release of calcium into the bloodstream. This condition is called hypercalcemia.
If you have these symptoms, tell a your healthcare provider or nurse right away. If
untreated, it may cause a coma.
If bone metastasis affects your bone marrow, you may have other symptoms that are
caused by lower blood cell counts. Your red blood cell levels may drop, causing anemia.
Signs of anemia are tiredness, weakness, and shortness of breath. If white blood cells
are affected, you may get infections. Signs of infection include fevers, chills, fatigue,
or pain. If your platelets are low, you may have bruising or abnormal bleeding.
It is important for you to discuss any of these symptoms with your healthcare provider
right away. Finding and treating bone metastasis early can help reduce complications.
How doctors find and diagnose bone metastasis
In some cases, your healthcare provider may find bone metastasis before you have symptoms.
In some cancers, where bone metastasis is common, your healthcare provider may do
tests to make sure the cancer has not spread to your bones, before recommending treatment.
When you have symptoms of bone metastasis, healthcare providers can use the following tests
to find the cause:
Bone scan. A bone scan can often find bone metastasis earlier than an X-ray can. The scan looks
at your whole skeleton. It allows the healthcare provider to check the health of all
the bones in your body. In a bone scan, you will get an injection with low level of
radioactive material. The amount is much lower than that used in radiation therapy.
The radioactive substance is attracted to diseased bone cells all over the body. This
helps diseased bone show up more clearly on the bone scan image.
CT scan. This imaging test shows detailed images of any part of the body, including the bones.
It is more detailed than a regular X-ray. It uses a combination of X-rays and computer
technology to make cross-sectional images of the body. These images are combined into
one detailed picture to show if cancer has spread to the bones.
MRI. An MRI scan uses radio waves and strong magnets, instead of X-rays, to make pictures
of bones and tissues. MRI provides cross-sectional images of the body, as a CT scan
does. It is very useful in looking at the spine and spinal cord, as well as joints.
Often, an MRI helps to further check a bone mass seen on an X-ray.
X-rays. An X-ray image can show where in the skeleton the cancer has spread. X-rays also
show the general size and shape of the tumor or tumors.
PET scan. This imaging test uses a type of sugar that is radioactive. This sugar is injected
into your blood. Cancer cells absorb large amounts of the sugar, compared to normal
cells. After the injection, you lie on a table in a PET scanner, while your whole
body is imaged. A special camera takes pictures of the radioactive areas found in
your body. A PET scan is not very detailed, but can sometimes find tumors too small
to be seen on other tests. If an abnormal area is seen, your doctor will likely order
another test for more information. This may be a CT scan or MRI. New technology combines
PET and CT scans for more detailed images all at once.
Lab tests. Bone metastasis can cause many substances to be released into the blood in amounts
that are higher than normal. Two such substances are calcium and an enzyme called
alkaline phosphatase. Blood tests for these substances can help diagnose bone metastasis.
Healthcare providers can also measure the levels of these chemicals over time to check
your response to treatment. But remember, higher levels of these substances can be
a sign of other health problems besides metastasis.
Biopsy. Your healthcare provider may suggest a bone biopsy to be sure a change is bone metastasis.
A sample of bone is removed and checked under a microscope. This is often done when
imaging tests and blood tests suggest, but don't confirm, you have metastasis.
How bone metastasis is treated
Bone metastases are treated with the same treatments used to treat the primary cancer.
For instance, metastatic prostate cancer in the bone may be treated with hormone therapy. In
addition to treating the primary cancer, these treatment options are available for
Bisphosphonates (medicines that slow down bone cells called osteoclasts)
Denosumab (another medicine that slows down osteoclasts)
Radiation therapy and radiopharmaceuticals (radioactive medicines)
Other treatments, including physical therapy and pain medicines
These medicines slow down the abnormal bone destruction and formation that bone metastases
cause. The medicines help do the following:
Decrease your risk for fractures
Reduce bone pain
Lower high blood calcium levels
Slow bone damage that metastases cause
Different types of bisphosphonates are available, such as:
Each medicine has somewhat different effects. Bisphosphonates in cancer treatment
are often given through a small, flexible tube called an IV (intravenous) line every
three to four weeks. They are also available as pills that you swallow. But the pills
are not well absorbed and can irritate the gastrointestinal (GI) tract. The side effects
of bisphosphonates are usually mild and don’t last long. Some of the most common side
Lack of appetite
Healthcare providers sometimes give this medicine in place of a bisphosphonate. It
is injected under the skin every four weeks. Side effects are much the same as those
caused by bisphosphonates.
Healthcare providers may also give denosumab if bisphosphonates stop working. Denosumab
can help prevent or delay problems like fractures in people with bone metastases.
Radiation therapy and radiopharmaceuticals
Radiation therapy uses strong ionizing X-rays to damage or destroy cancer cells. Radiation
is often helpful in easing pain and killing tumor cells in bone metastases. It may
also be used to help prevent fractures and to treat spinal cord compression. It may
take two to three weeks for the full effects of this treatment to occur. Side effects
of radiation may include skin changes in the area being treated. In rare cases, it
may cause a short-term increase in symptoms of bone metastasis.
Radiopharmaceutical therapy is another type of radiation. This approach involves injecting
a radioactive substance into a vein. The substance is attracted to areas of bone that
have cancer. Giving radiation directly to the bone in this way destroys active cancer
cells in the bone and can ease symptoms. It is often very useful if many bones are
affected. Side effects are rare.
Surgery may be done to prevent or treat a bone fracture. The surgery can involve removing
most of the tumor or stabilizing the bone to prevent or manage a fracture, or both.
Metal rods, plates, screws, wires, or pins may be inserted to strengthen or provide
structure to the bone damaged by metastasis.
This treatment involves putting a probe right into a tumor. A CT scan might be used
to guide the probe. Chemicals, electricity, heat, or cold is then passed through the
probe to destroy the tumor.
This treatment may be an option to treat a bone tumor that's causing problems. If
a hole is left behind, it might be filled with bone cement (below).
A quick-setting cement can be put into bone using a needle. This can help stabilize
the bone or strengthen it.
If the cement is put into the spinal bones, it's called vertebroplasty or kyphoplasty.
The bone cement is injected into one of the bones in the spine to help keep it from
collapsing. It's called cementoplasty if it's used to treat other bones.
This treatment may be used after other treatments that have been used to destroy the
tumor in the bone.
Other treatments for bone metastases and their symptoms include physical therapy and
pain control with or without medicine. Healthcare providers use many different medicines
or combinations of medicines to treat pain from bone metastases. The main types of
medicines used to treat this pain are nonsteroidal anti-inflammatory drugs (NSAIDs).
These include aspirin and ibuprofen. They stop substances called prostaglandins that
seem responsible for much bone pain. Other ways to manage pain without medicine include
using heat and cold, relaxation, and therapeutic beds or mattresses.