Cancer & Pathologic Fractures                                                          Printer-friendly version

Normal bone

To understand why pathologic fractures occur in some cancer patients, let's look at the life cycle of normal bone. Normal bone is an active tissue throughout your life (1). Small areas of bone are constantly being worn away by special cells called osteoclasts (1). The chemicals that made up the worn away bone are reabsorbed into the blood (1). New bone is then built up by other cells, called osteoblasts (1). Osteoblasts take chemicals from the blood to create this new bone (1). This process of breakdown and buildup is regulated by hormones and other chemicals that the cells secrete into the blood to communicate with one another (1).

Pathologic fractures in areas with bone metastases

In areas of bone metastases, the bone damage is greater than would be expected from tumor pressure on the bone (1). In fact, tumor cells secrete chemicals that stimulate osteoclasts (1). The osteoclasts wear away portions of bones (reabsorption) leaving holes in the bone, called osteolytic lesions (2). The tumor cells can also secrete chemicals that cause the build up of abnormal bone (2). This is called osteosclerotic bone (2). Both types of abnormal bone can be painful and are weaker than normal bone (2). Because this abnormal area of bone changes the way the entire bone bears weight, the structure of the normal bone surrounding the metastasis is under added stress and can be disrupted (1). This can lead to a pathologic fracture (abnormal break) of the bone.

Pathologic fractures

The bones that commonly have pathologic fractures are the ribs, the vertebral bodies (the bones that make up the spine) and the long bones close to the torso (the humerus and femur) (1). Rib fractures can lead to restricted breathing because of pain (1). Fractures of the vertebral bodies lead to loss of height and to restricted breathing because of the changed shape of the chest (1). Pathologic fractures decrease mobility and the ability to perform daily activities (3). They have an impact on outlook on life, often causing depression (3). In some cases, they have been shown to decrease survival (3).

Areas with bone pain and those that look worn away on x-ray are areas where the bone can fracture (1). The use of radiation, systemic therapy for the tumor, bisphosphonates, and if necessary, surgery, can help to prevent pathologic fractures (1).

Pathologic fractures and disability

The implications of having a pathologic fracture depend on the underlying tumor (1). Breast cancer has a long course and patients live a long time; a pathologic fracture can cause long-term disability (1). Lung cancer has a short course, so a pathologic fracture rarely leads to long-term disability (1). Pathologic fractures are not necessarily an indication of terminal disease (1). It is therefore important to understand that, if left untreated, they rarely heal (1). Surgery and radiation can restore mobility and decrease pain (1).

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References:

1. Coleman RE, Rubens RD. Bone Metastases. In: Abeloff MD, Armitage JO, Lichter AS, Niederhuber JE, eds. Clinical Oncology. 2nd Edition. Churchill Livingstone. 2000. pp 836-871.
2. "How Cancer Spreads" http://www.us.ZOMETA.com/info/cancerbones/index.jsp. Accessed 09/05/2003.
3. ZOMETA^® Monograph, Section 1.