Articles:Bone metastases
Metastases within bone can cause extreme and debilitating pain. Bone metastases are far more common than primary bone cancer, and many different cancer types can spread to the bone. The most common types of cancer which spread to bone are:
- Breast
- Prostate
- Lung
- Kidney
- Thyroid
Cancer can theoretically metastasize to any bone in the body, but in reality there is a predilection for certain sites. The most common sites are the vertebrae, ribs, pelvis, sternum, and the skull.
Types of bone metastasis
A bone is a rigid organ, but it is far from physiologically static. To maintain bone strength, there is continuous break down and simultaneous reformation of bone, two processes which must finely balance for good bone health.
Osteoblastic (or sclerotic) metastases are characterised by the deposition of new bone. These are present most commonly in prostate cancer, but also occur in carcinoid, small-cell lung cancer, medulloblastoma, and Hodgkin lymphoma. The molecular crosstalk between tumour and bone cells involves osteoblast generating proteins such as Transforming Growth Factor, Bone Morphogenic Proteins (BMPs), and Endothelin-1[1].
Osteolytic metastases are characterised by the destruction and breakdown of normal bone. These often occur when breast cancer spreads to bone, which is primarily mediated by osteoclasts (bone cells that breaks down bone tissue) and is not a direct effect of metastasized tumour cells[2]. Other tumour types with osteolytic metastases include multiple myeloma, non-small cell lung cancer, thyroid cancer, non-Hodgkin lymphoma, and Langerhans' cell histiocytosis. Osteolytic metastases are more common than osteoblastic metastases.
Mixed metastases is when a patient has both osteolytic and osteoblastic lesions together in the same area of bone. These metastases are usually present in metastatic gastrointestinal and squamous cancers, as well as in secondary breast cancer. Although breast cancer gives rise to predominantly osteolytic lesions, around 15–20% of women