Can a bone scan detect metastatic lesions?

From the Guidelines

Yes, bone scans can effectively detect metastatic lesions in bone, with a sensitivity ranging from 62% to 100% for detecting bone metastases in patients with late-stage breast cancer. A bone scan is a nuclear medicine imaging test that uses a radioactive tracer (typically technetium-99m) which is injected intravenously and accumulates in areas of increased bone turnover or metabolic activity. Metastatic lesions typically cause such increased activity, appearing as "hot spots" on the scan. Bone scans are particularly sensitive for detecting osteoblastic metastases (where bone formation occurs) from cancers like prostate, breast, and lung, as noted in studies such as 1 and 1.

The test can detect lesions months before they would be visible on regular X-rays, as bone scans can identify metabolic changes when as little as 5-10% of bone is affected. However, purely lytic (bone-destroying) metastases may sometimes appear as "cold spots" or be missed entirely. For comprehensive evaluation, bone scans are often used alongside other imaging modalities like CT, MRI, or PET scans. The procedure involves an injection followed by imaging 2-4 hours later, with the patient lying still under a gamma camera for about 30-60 minutes while images are captured.

Some key points to consider when using bone scans for detecting metastatic lesions include:

• The sensitivity of whole body bone scans for detecting bone metastases in patients with late-stage breast cancer ranges from 62% to 100%, regardless of tumor subtype, as reported in 1 and 1.
• Bone scans have a 98% sensitivity for detecting early bone metastasis in symptomatic patients, as noted in 1.
• The presence of peripheral metastasis almost always (>99%) occurs in the context of extraosseous or central osseous metastasis, and detection of additional peripheral metastases does not typically result in a change in management, as discussed in 1 and 1.
• Other imaging modalities like FDG-PET/CT may be superior to bone scans in detecting bone metastases, especially in cases of osteolytic metastases, as suggested in 1 and 1.

Overall, while bone scans are a useful tool for detecting metastatic lesions in bone, they should be used in conjunction with other imaging modalities and clinical evaluation to ensure accurate diagnosis and effective management. The choice of imaging modality should be based on the individual patient's needs and the specific type of cancer being evaluated, with consideration of the most recent and highest quality evidence, such as that provided in 1 and 1.

From the Research

Bone Scan Detection of Metastatic Lesions

• A bone scan can detect metastatic lesions, but its sensitivity and specificity vary depending on the type of cancer and the imaging technique used 2, 3, 4, 5.
• The sensitivity of bone scans for detecting metastatic lesions ranges from 29% to 93.4%, while the specificity ranges from 72.5% to 93.5% 2, 4.
• Bone scans are more sensitive for detecting bone metastases in certain types of cancer, such as non-small cell lung cancer, but may have lower sensitivity for other types, such as small cell lung cancer 2, 4.
• The use of correlative imaging techniques, such as single-photon emission computed tomography/computed tomography (CT) and magnetic resonance imaging (MRI), can help increase diagnostic confidence and avoid misinterpretation of benign diseases as metastatic lesions 3, 6.

Limitations of Bone Scans

• Bone scans may not detect all metastatic lesions, especially those outside the region scanned by the imaging technique 4.
• Benign diseases can cause false-positive results on bone scans, leading to diagnostic dilemmas 6.
• The presence of multiple new abnormalities on a bone scan increases the likelihood of skeletal metastases, but the proportion of scans reflecting metastases varies depending on the number and sites of new abnormalities 5.

Comparison with Other Imaging Techniques

• Positron emission tomography/computed tomography (PET/CT) has been shown to have higher sensitivity and accuracy than bone scans for detecting metastatic lesions in certain types of cancer, such as small cell lung cancer 4.
• MRI is more sensitive than bone scans for detecting bone metastases, especially in the spine, and can provide additional information on soft tissue involvement 3.