Bone Cancer

Question 1

What are the most common primary cancers that metastasize to bone?

Answer 1

Breast (blastic/sclerotic lesions)

Prostate (blastic/sclerotic lesions)

Lung (lytic lesions)

Thyroid (lytic lesions)

Kidney (renal cell carcinoma) (lytic lesions)

Question 2

What is the most common presentation of bone metastases?

Answer 2

Bone pain
(often localized to the affected bone)

Hypercalcemia
(osteoclastic activity releases calcium into the bloodstream)

Pathologic fractures
(weakened bones due to lytic lesions)

Neurologic symptoms
(if spinal metastasis compresses the spinal cord)

Question 3

What imaging study is most sensitive for detecting sclerotic bone metastases?

Answer 3

Bone scintigraphy (bone scan) with technetium-99m

Detects areas of increased osteoblastic activity.

It is highly sensitive for cancers that cause sclerotic metastases (breast, prostate).

Question 4

Why is alkaline phosphatase (ALP) elevated in bone metastases?

Answer 4

Bone turnover increases in response to osteoblastic activity.

Osteoblasts produce bone-specific alkaline phosphatase.

This leads to an increase in total serum alkaline phosphatase.

Question 5

Which bone imaging modality is best for detecting lytic bone metastases?

Answer 5

PET scan (positron emission tomography) or CT scan.

Lytic bone lesions are best seen with imaging modalities that detect changes in bone structure, like CT.

Lytic lesions occur in cancers like lung cancer, thyroid cancer, and renal cell carcinoma.