Can a DEXA Scan Show Cancer?

Dual-energy X-ray absorptiometry, more commonly known as a DEXA scan, is a specialized imaging technique widely used to assess bone mineral density (BMD). It is a non-invasive, low-radiation tool typically employed in diagnosing osteoporosis and evaluating fracture risk. Given its routine use, especially in aging populations and cancer patients undergoing certain therapies, a common question arises: can a DEXA scan detect cancer?

While DEXA scans are not designed to directly identify or diagnose cancer, emerging evidence suggests that under certain circumstances, they may incidentally reveal signs consistent with metastatic disease. This article aims to explain what a DEXA scan is capable of, how it might relate to cancer detection, and what the research says about its diagnostic limitations and possibilities.

Instalab Research

Understanding DEXA Scans

A DEXA scan works by using two low-energy X-ray beams to measure the density of bones, usually in the lumbar spine and hips. The results are presented as T-scores and Z-scores, which help evaluate bone strength and potential for fractures. DEXA scans are considered the gold standard for diagnosing osteoporosis, especially in postmenopausal women and men over 70.

Importantly, DEXA scans provide structural information, not cellular or metabolic data. This limits their ability to detect soft tissue changes or tumor cells. Unlike MRI, CT, or PET scans, DEXA lacks the resolution and contrast capabilities needed for detailed cancer imaging.

DEXA and Cancer Risk Assessment

In clinical oncology, DEXA scans are frequently recommended for cancer patients, not to detect tumors, but to monitor bone health. This is especially important in individuals receiving treatments like aromatase inhibitors or chemotherapy, which can accelerate bone loss.

For example, breast cancer patients treated with aromatase inhibitors are at high risk of reduced BMD and related fractures. National guidelines recommend baseline DEXA scans in these patients to ensure early intervention with bone-protective therapies. An audit study found that increasing DEXA scan compliance in newly diagnosed breast cancer patients significantly improved bone health management.

So while DEXA scans do not detect cancer itself, they are a crucial part of cancer care by helping manage secondary complications like osteoporosis.

Incidental Cancer Detection via DEXA

While not designed for it, there is limited but growing evidence that DEXA scans can sometimes detect signs that suggest the presence of cancer, particularly metastatic lesions in the bone.

A 2019 study investigated whether machine learning tools could help radiologists identify osteoblastic metastases—areas where cancer has spread to the bone and caused abnormal bone growth—on routine DEXA scans. These metastases, often from breast or prostate cancer, can appear as abnormally dense areas in the vertebrae. Researchers trained a random forest classifier to analyze lumbar spine data from 200 patients. The model achieved a sensitivity of 77.8% and specificity of 100% for detecting these lesions, outperforming traditional radiologist readings, which only identified 15.6% of metastatic cases on initial review.

This finding suggests that with advanced software support, DEXA scans may play a secondary role in alerting clinicians to possible metastatic bone disease, particularly in the spine. However, it must be emphasized that such incidental findings require follow-up imaging with more specialized techniques like MRI or CT for confirmation.

Limitations and Misconceptions

Despite this emerging utility, there are significant limitations to relying on DEXA scans for cancer detection:

Lack of specificity: Abnormal bone density could be due to a variety of causes, not just cancer. Degenerative changes, prior fractures, or benign growths can all mimic the appearance of metastases.
No soft tissue imaging: DEXA cannot assess organs or detect tumors in tissues such as the breast, liver, lungs, or brain.
False negatives: Many types of cancer-related bone damage, especially early lytic lesions (where bone is destroyed), may not be detected by DEXA due to their subtle presentation.

For these reasons, DEXA scans should never be used as a standalone cancer screening or diagnostic tool. If cancer is suspected based on symptoms, history, or other test results, dedicated imaging such as PET, CT, or MRI is far more appropriate.

The Bottom Line for Patients

A DEXA scan is not designed to detect cancer and should not be used as a diagnostic tool for this purpose. However, under certain conditions, especially with the assistance of machine learning algorithms, it may incidentally reveal signs of bone metastases, particularly in patients with known cancers such as prostate or breast cancer. These incidental findings should always be confirmed through more advanced imaging modalities.

For now, the most important role of DEXA scans in oncology remains the evaluation and management of bone health in patients undergoing cancer treatments. As technology evolves, their utility in detecting metastases may expand, but caution and clinical judgment must guide their interpretation.

References

Dong, H., Dayananda, P., Preece, S., & Carmichael, A. (2015). Are patients with newly diagnosed breast cancer getting appropriate DEXA scans? A District General Hospital experience. BMJ Quality Improvement Reports, 4. https://doi.org/10.1136/bmjquality.u209414.w3856.
Mehta, S., & Sebro, R. (2019). Random forest classifiers aid in the detection of incidental osteoblastic osseous metastases in DEXA studies. International Journal of Computer Assisted Radiology and Surgery, 14, 903-909. https://doi.org/10.1007/s11548-019-01933-1.