Metastases to the Bone

What is Metastases to the Bone?

Metastases is the term used to describe the spread of cancer from its site of origin to another location in the body. Bone is one of the most common locations in the body to which cancer metastasises. Any type of cancer can spread to the bone.The most common metastasising cancers are those of the breast, lung, kidney, thyroid and prostate.

Statistics on Metastases to the Bone?

Bone metastases are common, however, its true incidence is unknown, as it is dependent on the prevalence of certain types of cancers in the community which predispose to bone metastases.

Risk Factors for Metastases to the Bone

Bone metastases are found more commonly in middle-aged to elderly people; they are uncommon in children. The major cancer types which tend to metastasize to bone include multiple myeloma, breast, prostate, lung, kidney, and thyroid cancers. However, a number of factors are involved - the probability of bone metastasis can be assessed only by knowing the prevalence of the cancer and its preference for bone in a particular ethnic group.

Progression of Metastases to the Bone

Bone metastases results in injury to bone tissue. There are two types of bone lesions: lytic lesions, which destroy bone material, and blastic lesions, which fill up bone with extra cells. Normal bone is in a constant state of remodelling - being broken down and rebuilt. Cancer cells that have spread to the bone disrupt this balance between the activity of cells that break down bone (osteoclasts) and cells that make bone (osteoblasts).Bone metastases may be found anywhere in the skeleton, but generally occur in the central parts. More than 90% of all metastases are found in the back, pelvis, upper leg, ribs, upper arm, and skull. Complications of bone metastases include pain, increased risk of fracture, raised calcium levels in the blood, and a decreased blood cell count.

How is Metastases to the Bone Diagnosed?

Tests which may be done if bone metastases are suspected include:

Blood tests.
ECG (if the patient has an irregular heartbeat).
X-rays.
Whole body bone scan looking for metastases.
CT scan / MRI scan to assess local disease.

Prognosis of Metastases to the Bone

Once cancer has spread to the bone, prognosis tends to be poor and treatment is generally aimed at minimising symptoms and improving quality of life. Bone metastases often have a significant impact on a patient's quality of life by causing reduced mobility and pain, and complications such as high calcium levels, bone marrow suppression and fractures.

How is Metastases to the Bone Treated?

The goal of treatment for bone metastases is to relieve pain and reduce the risk of fracture. Treatment may consist of surgery, radiation therapy, pain medications, and/or bisphosphonate drugs.

Surgery may be required if there is immediate risk of fracture. Metal rods, plates, screws, wires, nails, or pins can be inserted to stabilise the bone at risk.
Radiation Therapy: For metastatic lesions without immediate risk of fracture, radiation is effective for reducing localised bone pain and progression of the cancer.
Medications: A groups of drugs called 'bisphosphonates' have been shown to reduce the risk of fractures caused by metastatic bone lesions, as well as treating bone pain and controlling raised calcium levels. Painkillers may be required if bone pain is interfering with the patient's quality of life.

Metastases to the Bone References

Hetzel M, et al. Reliability of symptoms to determine use of bone scans to identify bone metastases in lung cancer: prospective study. BMJ 2004;328:1051-1052
Kmietowicz Z. Patients with bone metastases need better care. BMJ 1998;317:1547
Peh W. Bone metastases. eMedicine 2002.[available online @ http://www.emedicine.com/radio/topic88.htm]
Walling A. Effect of Bisphosphonate Therapy on Bone Metastases, Am F Phys. [available online @ http://www.aafp.org/afp/20040301/tips/20.html]