A DEXA scan uses low-dose X-rays to measure bone density and strength. It is commonly done to check for osteoporosis or bone weakening but not specifically to look for cancer.

If you’re worried about bone cancer, you may be wondering which tests are the best for diagnosing the condition. We’ll take you through the options your clinician may recommend to detect bone cancer, from bone scans and X-rays to biopsies and MRI scans.

What is a DEXA scan?

A DEXA (dual-energy X-ray absorptiometry) scan is an imaging scan that uses low-dose X-rays to check the mineral density of your bones. You might also hear it referred to as a bone densitometry scan. It’s commonly used to check for signs of osteoporosis rather than bone cancer. However, if you have treatment for bone cancer, your clinician may recommend a DEXA scan to check the health of your bones after treatment.

It’s a simple, painless procedure that checks how much X-ray gets absorbed by your bones to calculate their density and strength. It takes about 10-20 minutes. You'll lie flat on a padded table while a scanning arm passes over your body. The scanner uses very low doses of X-ray beams to take pictures of your bones, usually focusing on your spine, hips, and sometimes the full body. You just need to remain still while the images are taken.

What is bone cancer?

Bone cancer is a rare form of cancer in the UK and affects around 500 people each year. It’s more common in children, teens and young people.

Primary bone cancer (bone sarcoma) starts in the bones' cells. If cancer spreads from another part of the body into the bones, doctors call this secondary bone cancer.

What are the symptoms of bone cancer?

The main symptoms of bone cancer include:

Bone pain that is persistent and gets worse over time.
Pain in a different area from the affected bone (referred pain).
A lump, swelling or redness near a bone.
Difficulty moving a joint near an affected bone.
Problems with mobility, such as a limp.
Feeling more tired than usual.
Having a high temperature.
Unexplained weight loss.

More rarely, a fracture can be a symptom of bone cancer, as the bone has been weakened.

Can a DEXA scan show bone cancer?

Not directly, no. Experts use DEXA scans to check bone density rather than to look for tumours. While it may be possible to detect abnormalities in the DEXA scan that are signs of cancer, your clinician will not recommend a DEXA scan to diagnose cancer because there are much more effective scans available to do this.

You may need a DEXA scan if you are currently receiving cancer treatment or have had cancer treatment in the past. Some cancer treatments can cause your bones to become thinner and less dense over time. This makes your bones weaker and more likely to break or fracture easily. This condition of having weak, brittle bones is called osteoporosis. Your clinician will recommend a DEXA scan if they think you may have osteoporosis.

What other tests are used to diagnose bone cancer?

Your clinician will recommend a combination of tests to diagnose bone cancer. These may include:

X-ray: An X-ray shows the structure of bones and can reveal abnormal bone growths and areas of bone damage. However, it’s less effective at detecting early bone cancers or tumours in surrounding soft tissues.
Bone scan: A bone scan involves injecting a small amount of radioactive tracer material, which collects in areas of abnormal bone activity and tumours, highlighting any ‘hot spots’ on the scan images that may indicate cancer.
CT scan: A CT scan uses X-rays to create detailed cross-sectional images showing a bone tumour's exact location, size and shape. They can also help detect whether cancer has spread into soft tissues around the bone.
MRI scan: An MRI scan uses strong magnetic fields and radio waves to create detailed images that are the gold standard for evaluating tumours. It can also distinguish between cancer and some non-cancerous bone lesions.
Bone or bone marrow biopsy: A biopsy involves removing a bone or bone marrow sample with a hollow needle, and the tissue is examined under a microscope to confirm if it is cancerous.
Blood tests: Blood tests can measure levels of certain enzymes in the blood. If the levels of enzymes like alkaline phosphatase and lactate dehydrogenase are higher than normal, it may be a sign that a rapidly growing bone tumour is present.

What does cancer look like on a bone scan?

When you have a bone scan, the radioactive tracer will collect in areas of the bones where there is abnormal activity. These show up as bright and intense ‘hot spots’ on a bone scan and will look darker than the surrounding bones.

On an X-ray, bone cancers look like abnormal areas or growths that disrupt the normal, smooth appearance of the bone. However, X-rays may not show early or small bone cancers very well.

On a CT scan result, bone cancers typically appear as areas of bone destruction, abnormal bone growths, or dense masses extending into the surrounding tissues.

On an MRI scan result, bone cancers show up as abnormal masses that look different from normal bone and muscle tissues. MRIs are especially good at seeing if the cancer has grown into the surrounding areas.

Conclusion: Does a bone density test show cancer?

A bone density test or DEXA scan is not used to diagnose bone cancer. While a DEXA scan provides some information about bone health, different imaging tests are required for properly diagnosing bone cancers.

Other tests like X-rays, CT scans, MRIs, and bone scans are much better for seeing if there are any abnormal growths or damage to the bones that could be cancer. Your clinician may also need to do a biopsy, taking a small sample of the bone, to confirm if it is cancer.

Book a DEXA scan if you’re worried about your bone health. If you are concerned about bone cancer and are unsure which scan is best for you, book a consultation with one of our clinicians. They can give you the advice and information you need, and there’s no obligation to book a scan afterwards.