Metastatic Bone Disease and Pathological Fractures

Metastatic bone disease (MBD) is cancer that originates in one area of the body, such as an organ, gland or tissue, and then spreads to bone. Because it can weaken the bone it can lead to pathological fractures. The most common bones impacted are the spine, pelvis, ribs, skull, upper arm and long bones of your leg. 

Types & Stages

There are three types of metastatic bone disease:

• Osteolytic. The tumor can completely destroy the bone in a particular area, a process called osteolytic bone destruction. Or a new bone can form in response to the cancer spread, resulting in osteoblastic lesions. 
   
  • Because MBD weakens the affected bones, you can be at risk for fractures. Broken bones caused by MBD are called pathological fractures. If the bone has not yet broken but is so weak that a break is imminent, this is referred to as an impending pathologic fracture.
     
• Osteoblastic (or sclerotic). This is characterized by an abnormal formation of new bone, present in prostate cancer, carcinoid, small cell lung cancer, Hodgkin lymphoma or medulloblastoma (a malignant brain tumor).
   
• Mixed. The presence of both osteolytic and osteoblastic lesions.

Signs & Symptoms

Sometimes bone metastasis causes no signs or symptoms. Symptoms may include:

• bone pain
• broken bones
• high levels of calcium in the blood, which is called hypercalcemia and can cause nausea, vomiting, constipation and confusion
• pain and stiffness in the neck or back from pressure on the spinal cord
• leaking urine, called urinary incontinence
• sudden urge to urinate, called urinary urgency
• not being able to control the passing of stool and stool leaking from the bowel
• weakness in the arms and legs

Diagnosis

Tests and procedures to diagnose metastatic bone disease may include:

• Imaging tests. These may include: 
   
  • X-rays. A diagnostic test that uses invisible electromagnetic energy beams to produce images of internal tissues, bones and organs onto film.
     
  • Computerized tomography scan (CT or CAT scan). A diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. 
     
  • Magnetic resonance imaging (MRI). A diagnostic procedure that uses a combination of large magnets, radiofrequencies and a computer to produce detailed images of organs and structures within the body. 
     
  • Bone scans. A whole-body bone scan is a nuclear medicine test to check your bones for issues or changes. You receive an injection of a substance called a radiotracer. The radiotracer collects in areas of irregular activity and highlights these areas on an imaging scan. 
     
  • Positron emission tomography scan (PET scan). An imaging test that uses a radioactive drug called a tracer—most often injected into a vein in your hand or arm—to show both typical and atypical metabolic activity. The PET images are typically combined with CT or MRI and are called PET-CT or PET-MRI scans.
     
• Biopsy. A procedure to remove some cells for testing. The sample might be removed with a needle put through the skin. Or the sample might be taken during surgery to remove the cancer. The type of biopsy depends on the cancer's location.

Treatment

The most common treatments for MBD include:  

• Bone-building medicines. Help to strengthen the bones and reduce the pain caused by bone metastasis. This lowers the need for strong pain medicines. Bone-building medicines also may lower the risk of getting new bone metastasis.
   
• Radiopharmaceutical medicines. Contain a low level of radioactive material and are given through a vein to target the bones and might be an option when there is more than one bone metastasis.
   
• Chemotherapy. If cancer has spread to more than one bone, your doctor may suggest chemotherapy.
• Hormone therapy. Hormone-blocking treatments may help control the cancer.
   
• Pain medicines. Work to control the pain bone metastasis causes. 
   
• Targeted therapy. Uses medicines that attack specific chemicals in the cancer cells. 
   
• Radiation therapy. Can treat one or a few areas of bone metastasis, but it typically isn't used if there are many areas. Radiation can't rebuild bone weakened by cancer. But it can help ease pain and control the growth of the bone metastasis.
   
• Stereotactic body radiotherapy. A highly precise, intense radiation treatment that might be used for bone metastasis in the spine bones. 
   
• Surgery. Surgical procedures can help a bone that is at risk of breaking or repair a broken bone. Operations used for bone metastasis include:
   
  • Surgery to make the bone more stable. If a bone is in danger of breaking due to bone metastasis, surgeons can use metal plates, screws and rods to stabilize it. This procedure is called orthopedic fixation.
     
  • Surgery to inject cement into a bone. Bone cement might help broken bones that can't be made stable with metal plates or screws. These include pelvic bones and bones in the spine.
     
  • Surgery to repair a broken bone. If bone metastasis causes a bone to break, surgeons may work to repair the bone. This may involve using metal plates, screws and nails to make the bone stable. Joint replacement, such as a hip replacement, may be another choice.
     
• Ablation therapy. Applies treatment directly to the cancer cells using heat or cold to kill cancer cells. Ablation therapy may help control pain caused by bone metastasis. It may be a choice if you have one or two areas of bone metastasis that other treatments haven't helped. During an ablation therapy procedure called radiofrequency ablation, a needle with an electric probe is put into the cancer. Electricity passes through the probe and heats the tissue around it. After the tissue cools, the process is done again. An ablation therapy procedure called cryoablation freezes the cancer and then lets it thaw. After the tissue thaws, the process is done again.

Causes & Risk Factors

Metastatic bone disease is caused by cancer that starts in one area and spreads to a bone. Some types of cancer have a higher risk of causing bone metastasis than others do. Cancers more likely to spread to the bones include:

• breast cancer
• kidney cancer
• lung cancer
• lymphoma
• melanoma
• multiple myeloma
• prostate cancer
• thyroid cancer

Screening

There is no routine screening test for metastatic bone disease.