|
The first symptom of bone metastasis is almost always pain.
If you have cancer and begin to experience pain in a bone, you should
report it to your doctor right away. Sometimes, if the cancer isn't
promptly treated, the bone may break. Your doctor will want to x-ray
the painful area and do scans or other imaging tests. Other diseases,
such as bone infections, arthritis, or just being very active, can also
make bones hurt.
When a cancer is first diagnosed, doctors will recommend a series of
other tests to find out how far it has spread. Depending on certain
features of the primary tumor (such as its size and exact type), your
doctors will estimate your risk of metastasis and may recommend tests
to search for it. If no metastases are found, then the primary cancer
will be treated and you will see the doctor at regular intervals for
follow-up care. One of the main purposes of follow-up care is to find
out if the cancer is beginning to come back either at the original site
or elsewhere at a metastatic site.
Symptoms of Bone Metastasis
The symptoms of bone metastasis can be mild at first. You
may notice your appetite decreasing and have trouble sleeping because
you are uncomfortable. These symptoms can make it hard to perform your
usual activities.
Bone Pain
Bone pain is usually the first symptom of metastasis to the
bone. The pain often comes and goes at first. It tends to be worse at
night and may be relieved by movement. Later on, it becomes constant
and may be worse during activity. It is important to tell your doctor
about bone pain. The bone might be so weakened that it will break. This
can often be prevented if the bone metastasis is found early.
Fractures
Broken bones (fractures) can occur and cause severe pain.
They may keep you from moving much at all. In some cases, a fracture is
the first sign of bone metastasis. The most common sites of fractures
are the long bones of the arms and legs and the bones of the spine.
Sudden pain in the middle of the back, for example, is a common sign of
a cancerous bone breaking and collapsing.
Spinal Cord Compression
Cancer in the backbone can press on the spinal cord. The
spinal cord contains nerves that allow you to move and feel what
happens to your body. This is why pressure on the spinal cord is one of
the most serious complications of bone metastasis. Not only can the
pressure on the spinal cord cause pain, it can damage your spinal cord
so that your legs become numb and even paralyzed. Sometimes the first
symptom you may have of spinal cord pressure is trouble urinating
because nerves from the spinal cord control the bladder.
Hypercalcemia
If the cancer has metastasized to many bones, you may develop
hypercalcemia (high blood calcium levels caused by release of calcium
from bones). This can cause nausea, loss of appetite, thirst, and
extreme tiredness. If left untreated, hypercalcemia can even cause you
to lapse into a coma.
For these reasons, it's very important for you to tell your doctors and
nurses about any new bone symptoms or changes in old symptoms. Early
detection and early treatment of bone metastasis can help reduce your
chances of further problems later on.
Sometimes bone metastases are found before they have a chance to cause
any symptoms. Signs of bone metastases may be found through lab and
imaging tests (such as bone x-rays or bone scans) that are done when
the doctor is learning the stage of your cancer (called staging), or in
a routine checkup after treatment is finished.
Imaging Tests to Detect Bone
Metastasis
X-rays
During staging or follow-up of a cancer, your doctor may get
x-rays of your bones. These may show evidence of the cancer's spread to
one or more bones. X-rays will not show bone metastases unless the
cancer has destroyed about half of the bone’s substance.
Bone metastases can change the appearance of bone in 2 ways.
One way is when metastases dissolve some of the minerals in the bone,
which makes the bone less dense. These are called osteolytic or lytic metastases,
and appear on x-rays as a dark hole in the gray-white bone image. Bones
with osteolytic metastases tend to break very easily.
Other cancers, especially prostate cancers and some breast
cancers, cause osteoblastic
or blastic metastases. These make the bone appear denser
(sclerosis). On x-rays, these metastases appear as spots that are
whiter than the surrounding bone. This is the second way metastases can
change the way bones look.
X-rays can also find fractures (breaks) in bones that are
weakened by metastases.
Radionuclide Bone Scan
A radionuclide
bone scan helps show whether a cancer has metastasized to
bones. You will be given an injection of a radioactive substance called
technetium diphosphonate. The injection itself is the only
uncomfortable part of the entire scanning procedure. The amount of
radioactivity used is low compared with the much higher doses used in
radiation therapy, and this low level of radiation does not cause any
side effects.
The radioactive substance is attracted to diseased bone cells
throughout the entire skeleton. Areas of diseased bone will be seen on
the bone scan image as dense gray to black areas called hot spots.
These areas may suggest metastatic cancer, although arthritis,
infection, or other bone diseases can also cause hot spots. The
pattern of these diseases is usually different from the pattern caused
by cancer. To tell the difference between these conditions, the cancer
care team may use other imaging tests or take bone biopsies. Bone scans
can find metastases much earlier than regular x-rays. Not only are bone
scans useful in spotting bone metastases, they can also track how
metastases respond to treatments.
Sometimes bone scans fail to find areas of cancer spread to
the bones. This happens most often if the metastases are osteolytic. In
some patients, the scan may show no radioactivity in certain areas of
bone that have already been destroyed by the cancer.
Computed Tomography
The computed
tomography (CT)
scan is an x-ray procedure that produces detailed cross-sectional
images of the body. Instead of taking one picture, like the usual
x-ray, a CT scanner takes many pictures as it rotates around you. A
computer then combines these pictures into an image of a slice of your
body. The machine will take pictures of many slices of the part of your
body that is being studied. This test can help tell whether your cancer
has spread into your bones. It is especially important when the bone
metastases are only osteolytic, since these metastases sometimes don't
show up in bone scans. Often, after the first set of pictures is taken,
you will receive an intravenous injection of a "dye" or radiocontrast
agent that helps better outline structures in your body. A second set
of pictures is then taken.
CT scans can also be used to precisely guide a biopsy needle
into a suspected metastasis. For this procedure, called a CT-guided needle biopsy,
you stay on the CT scanning table, while a radiologist advances a
biopsy needle toward the suspicious area. CT scans are repeated until
the doctors are confident that the needle is within the mass. A fine
needle biopsy sample (tiny fragment of tissue) or a core needle biopsy
sample (a thin cylinder of tissue about ½ inch long and less than 1/8
inch in diameter) is removed and examined under a microscope.
CT scans take longer than regular x-rays, and you need to lie
still on a table for 15 to 30 minutes while the scans are being done.
But just like other computerized procedures, CT scanning is getting
faster and your stay might be fairly short. However, you might feel a
bit confined by the equipment you have to lie in while the pictures are
being taken.
The contrast dye will be injected through an IV (intravenous) line.
A few people are allergic to the dye and get hives, a flushed feeling,
or rarely, more serious reactions like trouble breathing and low blood
pressure. Be sure to tell the doctor if you have ever reacted to any
contrast material used for x-rays.
Magnetic Resonance Imaging
Magnetic
resonance imaging (MRI) scans use radio waves and strong
magnets instead of x-rays. The energy from the radio waves is absorbed
and then released in a pattern formed by the type of tissue and by
certain diseases. A computer translates the pattern of radio waves
given off by the tissues into a very detailed image of parts of the
body. Like a CT scanner, MRI produces cross-sectional slices of the
body, but it can also produce images that are parallel with the length
of the body. A contrast material might also be used in MRI scans, but
less often than with CT scans.
MRI scans are particularly useful for looking at the spine and
spinal cord. If your doctor thinks your cancer is pressing on your
spinal cord, this is the best test to find out. MRI scans are a little
more uncomfortable than CT scans. First, they take longer—often up to
an hour. Also, you are placed inside a tunnel-like structure, which is
somewhat confining. The machine also makes a mild thumping noise that
bothers some people. Some testing centers will provide headphones with
music to block out this sound. In general, most people tolerate the
procedure well.
Positron Emission Tomography
Positron
emission tomography (PET) is usually performed with
glucose (a form of sugar) that contains a radioactive atom. A small
amount of the radioactive material in injected into a vein. Cancer
cells in the body absorb large amounts of this radioactive sugar. A
special camera is used to detect the radioactivity. PET scanning is
useful to see whether the cancer has spread to lymph nodes. PET scans
are also useful when your doctor thinks the cancer has spread, but
doesn’t know where. PET scans can be used instead of several different
x-rays because they scan your whole body. Newer devices combine a CT
scan with a PET scan to better pinpoint the tumor.
Blood Tests to Detect Bone
Metastasis
Serum Tumor Markers
Some types of cancer release certain substances, called tumor markers, into
the bloodstream. Patients with these types of cancer may have blood
tests at regular intervals to see if levels of these markers are
rising. For example, high
prostate-specific antigen (PSA) levels in a man who has
already had surgery or radiation therapy for prostate cancer suggest
the cancer may have come back or, especially if the levels are very
high, may have spread to the bones. A high blood calcium level is
another sign that the cancer may have spread to the bones.
Other Blood Tests
When cancer spreads to certain organs, it may damage the cells
of the organ or change the way they work. This may produce certain
substances that can be found by routine blood tests. For example, bone
metastases often cause high levels of alkaline phosphatase. Although
this substance is made by both the liver and bones, there are special
chemical tests that can tell if it comes from bone.
Urine Tests
Several substances are produced when bone is damaged. These
are often secreted into the urine. One such substance that can be
measured is called N-telopeptide.
Tissue and Cell Sampling Tests
Used to Find Bone Metastasis
If you have had cancer in the past, your doctor can usually
diagnose metastatic cancer based on how the bone scan or other x-rays
look. If any of your blood tests also suggest metastatic cancer, this
makes the diagnosis even more certain. Because of this, biopsies are
usually not needed. But if the diagnosis is not clear, your doctor will
need a biopsy sample from the abnormal area to find out if it is
cancer.
Needle Biopsy
There are 2 types of needle biopsies: fine needle and core
needle.
Fine Needle Biopsy or Aspiration
With fine
needle aspiration (FNA), a very thin needle and a syringe
are used to take a small amount of fluid and small tissue fragments
from the tumor. The doctor can aim the needle at a suspicious tumor or
area that can be felt near the surface of the body. This type of biopsy
of the bone is done only if the bone is weakened or if the cancer has
spread into the soft tissue around the bone. The biopsy is done after
numbing the area with a local anesthetic. It may be uncomfortable, but
is not very painful.
There are times that the suspicious area cannot be felt or
seen because it is deep inside the body. Or the suspected metastasis
may be seen on an x-ray but there is no lump that can be felt on the
surface of the bone. In these cases, the needle can be guided by
watching it during a CT scan.
Core Needle Biopsy
One approach your doctor might take is to do a standard bone marrow biopsy.
In this procedure, the doctor puts a needle through the back of your
pelvic bone after it has been numbed with local anesthetic. This can be
moderately uncomfortable. A core of bone and marrow will be removed.
Often, this test will show cancer even though cancer has not been seen
on x-rays of the pelvis. The benefit of this approach is that it is
simpler than trying to biopsy the suspicious sites because they may be
hard to get at or particularly painful to biopsy. But if there is a
real question about a particular area of bone then it can be biopsied
with a needle.
Usually, the doctor who performs a bone marrow biopsy uses
x-rays or CT scans for guidance. The needles used for a core biopsy
remove a small cylinder of tissue (about 1/16 inch in diameter and 1/2
inch long).
Surgical Bone Biopsy
Sometimes, needle biopsies don't provide an answer and a
surgical biopsy is needed. In this procedure, called an incisional biopsy,
the surgeon cuts into the bone to remove a small part of the tumor.
This procedure is not done very often.
Last Revised: 03/09/2007
|