Tests for Osteosarcoma

This is often the first test done if a bone tumor is suspected. Doctors can often recognize a bone tumor, such as an osteosarcoma, based on x-rays of the bone. Other imaging tests might be needed as well. Even if imaging strongly suggests a person has osteosarcoma, a biopsy (described below) will still be needed to confirm.

X-rays can also be used to see if a cancer has spread to the lungs. It can find larger tumors, but it is not as good as a CT scan for spotting smaller tumors. If a CT scan of the chest is done, an x-ray may not be needed.

MRIs create detailed images of soft tissues in the body using radio waves and strong magnets instead of x-rays, so there is no radiation. A contrast material called gadolinium may be injected into a vein before the scan to help see details better.

An MRI is often done to get a more detailed look at a bone mass seen on an x-ray. MRIs can usually show if the mass is likely to be a tumor, an infection, or some type of bone damage from another cause.

MRIs can also help determine the extent of a tumor and small bone tumors several inches away from the main tumor (called skip metastases). Knowing the extent of an osteosarcoma is very important when planning surgery.

An MRI scan usually shows better details than a CT scan (described below).

A CT scan combines many x-ray pictures to make detailed cross-sectional images of the inside of the body. If a bone x-ray shows a tumor, CT scans are sometimes used to see if the tumor has grown into nearby muscle, fat, or tendons, although MRI is often better for this.

A CT scan of the chest is often done to look to see if cancer has spread to the lungs and, potentially, other parts of the body.

Before the test, you or your child may get an IV (intravenous) injection of a contrast dye. These medicines can be used to get a clearer picture.

CT-guided core needle biopsy: CT scans can also be used to help guide a biopsy needle into a tumor.

For a PET scan, a radioactive substance (usually a type of sugar called FDG) is injected into the blood. The amount of radioactivity used is very low and will pass out of the body within a day or so. Because cancer cells are growing quickly, they absorb large amounts of radioactive sugar.

After about an hour, you (or your child) will be moved onto a table in the PET scanner. They will lie on the table for about 30 minutes while a special camera creates a picture of areas of radioactivity in the body. Younger children may be given medicine to help them stay calm or even sleep during the test.

PET scans can help show the spread of osteosarcomas to the lungs, other bones, or other parts of the body. PET scans can also be done again during treatment to see how well it is working.

Some machines can do a PET and CT scan at the same time (PET/CT scan). This lets the doctor compare areas of higher radioactivity on the PET scan with the more detailed image of that area on the CT scan.

A bone scan can help show if a cancer has spread to other bones and can be a part of the workup for people with osteosarcoma. This test is useful because it can show the entire skeleton at once.

For this test, a small amount of low-level radioactive material, called technetium-99, is injected into the blood and travels to the bones. A special camera that can detect the radioactivity creates a picture of the skeleton. Being still during this test is important. Younger children may be given medicine to help them stay calm or sleep during the test.

Areas of active bone changes attract the radioactivity and appear as “hot spots” on the scan. Hot spots may suggest cancer, but other bone diseases can also cause the same pattern. To make an accurate diagnosis, other tests such as plain x-rays, MRI scans, or even a biopsy might be needed. The amount of radioactivity used in this test is very low, and the material passes out of the body within a day or so.

A bone scan might not be needed if a PET scan is done.

In a surgical biopsy, a doctor (typically an orthopedic surgeon) removes a piece of the tumor through a cut made in the skin. These biopsies are usually done in an operating room with the patient under general anesthesia (asleep). They can also be done using a nerve block, which numbs a large area of the body.

For this type of biopsy, a thin, hollow needle is inserted through the skin and into the tumor to remove a small sample. If the tumor is deep, a CT scan or ultrasound may be used to help guide the needle into the tumor. It is important that a large enough sample is taken to get a diagnosis, which may mean the needle is stuck into the tumor multiple times. Just like a surgical biopsy, the procedure needs to be performed by someone with experience with bone sarcomas.