DEXA scans: how often and what the T-score means

A DEXA scan, dual-energy X-ray absorptiometry, is a quick, painless test that measures bone density, usually at the hip and lower spine. It uses a very small amount of radiation, far less than a standard chest X-ray. After breast cancer, it is used to check for bone thinning caused by early menopause, aromatase inhibitors such as letrozole or anastrozole, or ovarian suppression. The result is reported as a T-score, which compares your bone density with that of a healthy young adult. A T-score near zero is normal, a moderately negative score means osteopenia, and a more negative score means osteoporosis. Your doctor uses the T-score, along with other risk factors, to decide whether you need bone-strengthening treatment.

Who usually needs a scan

Women starting an aromatase inhibitor, those on ovarian suppression, women with early menopause after chemotherapy, and anyone with other risk factors for osteoporosis.

How often scans are repeated

Commonly every one to two years during aromatase inhibitor treatment, depending on the first result and whether treatment was started. Your team sets the interval.

What the scan cannot show

A DEXA scan measures bone density, not whether cancer has spread to bone. Other scans are used to look for bone metastases.

The T-score is a useful guide, but it is only one part of assessing fracture risk. Two women with the same score can have quite different risks depending on age, previous fractures, family history, weight and medicines.

Treatment decisions use more than the score

Many oncologists and bone specialists combine the T-score with a fracture risk tool and clinical factors to decide whether to start bone medicines. For women on aromatase inhibitors, the threshold for treatment is sometimes lower than for other women.

Scores vary slightly between scans

Small differences can occur between machines and centres. Having repeat scans on the same machine gives the most reliable comparison.

Spine readings can mislead

Arthritis or old fractures in the spine can make readings look higher than the true bone strength, which is why the hip is also measured.

What this page cannot tell you

It cannot interpret your own report. Ask your doctor to explain your scores and what they mean for treatment.

DEXA scanners are available in many hospitals and diagnostic centres in larger cities, and increasingly in smaller towns.

Choose a consistent centre

Where possible, have repeat scans at the same centre on the same type of machine for accurate comparison.

Check the report

A good report lists T-scores for the spine and hip regions and may include a fracture risk estimate.

Bring earlier reports

If you have had scans elsewhere, bring the reports so the new result can be compared with your previous scores and any change in bone density can be judged properly.

Cost

DEXA scans are generally affordable compared with other imaging. Ask your centre for the current charge.

A DEXA scan is usually combined with a few simple tests to look for other causes of bone loss.

Blood tests

Vitamin D, calcium, kidney function and sometimes thyroid or parathyroid hormone tests can reveal treatable causes.

A fracture risk estimate

Tools such as FRAX combine your scan result with age, weight, previous fractures, family history, smoking and medicines to estimate your chance of a major fracture. This helps decide whether treatment is worthwhile.

Height and posture

Losing height or developing a stooped back can signal spinal fractures, and may prompt an X-ray of the spine.