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's called bone
Cancer cells that have spread to the bone can damage the bone and cause symptoms.
Different treatments can be used to control the symptoms and the spread of bone metastases.
To better understand what happens in metastasis, it helps to understand more about
Bone is a type of connective tissue made up mostly of minerals, like calcium, 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 in a process called remodeling.
Two kinds of cells help with this:
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 protect vital organs, for instance, the ribs protect the lungs and heart.
Bones store and release minerals, like 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 far
from where it started 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 parts of the body. These cancers
commonly spread to the bones:
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, like osteosarcoma and Ewing sarcoma.
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 (primary) tumor site.
For instance, lung cancer that spreads to the bone is made of lung cancer cells. In
this case, the 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 affect 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.
They 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. They're 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 these 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's usually worse at night or with 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 causes.
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 problem is called hypercalcemia. If you have these symptoms, tell your healthcare provider or nurse right away. If
untreated, high calcium levels 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 bruise or bleed very easily.
It's 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, tests might be done to make sure
the cancer has not spread to your bones before a treatment plan is made.
When you have symptoms of bone metastasis, these are some of the tests that can be
Bone scan. A bone scan can often find bone metastasis earlier than an X-ray can. The scan looks
at your whole skeleton, so all the bones in your body can be checked for cancer. In
a bone scan, a mildly radioactive tracer is put into your blood through a vein. The
tracer is attracted to diseased bone cells all over your body. This helps diseased
bone show up more clearly on the scan.
CT scan. This test shows detailed images of any part of the body, including the bones. It's
more detailed than a regular X-ray. It uses a combination of X-rays and computer technology
to make cross-sectional images of the inside of the body. These images are combined
into detailed pictures 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 makes cross-sectional images of the inside of the body.
It's very useful in looking at the spine and spinal cord, as well as joints. Often,
an MRI helps to get a better look at the outline of a bone mass seen on an X-ray.
X-rays. An X-ray 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's radioactive. This sugar is put 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 machines combine 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. Blood tests
can be done to see if there are higher amounts than normal. Two such substances are
calcium and an enzyme called alkaline phosphatase. Blood tests for these substances
can help diagnose bone metastasis. These levels can also be used to 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, too, not just metastasis.
Biopsy. Your healthcare provider may suggest a bone biopsy to be sure a change is bone metastasis.
A small piece of bone is removed and tested for cancer cells. 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.
Along with treatment for the primary cancer, these treatments can be used for bone
Bisphosphonates (medicines that slow down bone cells called osteoclasts, which break
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 breakdown that bone metastases cause.
They help to:
Decrease your risk for fractures
Reduce bone pain
Lower high blood calcium levels
Slow bone damage that metastases cause
Bisphosphonates in cancer treatment are often given through a small, flexible tube
called an IV (intravenous) every 3 to 4 weeks. They can also be taken as pills that
you swallow. But the pills are not well absorbed and can irritate the gastrointestinal
The side effects of bisphosphonates are usually mild and don’t last long. Some of
the most common side effects are:
Lack of appetite
Bone or joint pain
Sometimes this medicine is used in place of a bisphosphonate. It's given as a shot
(injection) under the skin every 4 weeks. Side effects are much the same as those
caused by bisphosphonates.
Denosumab might be given if bisphosphonates stop working. It can help prevent or delay
problems like fractures in people with bone metastases.
Radiation therapy and radiopharmaceuticals
Radiation therapy uses strong beams of X-rays to damage or destroy cancer cells. Radiation
often helps ease pain and kill tumor cells in bone metastases. It may also be used
to help prevent fractures and to treat spinal cord compression. It may take 2 to 3
weeks to get the full effects of this treatment. 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 treatment involves
putting a radioactive substance into your blood through a vein. The substance is attracted
to areas of bone that have cancer. Giving radiation right to the bone in this way
kills active cancer cells there and can ease symptoms. It's 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, stabilizing the bone to prevent or manage a fracture, or both.
Metal rods, plates, screws, wires, or pins may be out in 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 from the inside.
This treatment may be an option to treat 1 or 2 tumors that are causing problems.
If a hole is left behind, it can be filled with bone cement (below).
A quick-setting cement or glue can be put into bone using a needle. This can help
stabilize the bone and/or strengthen it.
If 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. Many different medicines or combinations of
medicines can be used to treat pain from bone metastases. The main types of medicines
used to treat this pain are nonsteroidal anti-inflammatory drugs (NSAIDs), like 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.