Definition & Facts
Metastasis is the spreading of cancer from its primary site (the part of the body where the cancer originated) to another part of the body. If the part of the body that the cancer spreads to is bone, bone metastasis or metastatic bone disease is the result. Cancerous cells are carried by either the bloodstream or lymphatic vessels to tissues or other organs of the body.
Sometimes, the cancer cells break away from the tumor but do not cause any problem because they simply die. However, there are times in some patients that the cancerous cell grows and also forms new tumors. When this happens, the cancer is said to have metastasized. The single tumor resulting is a metastatic tumor.
There are also times the metastatic tumors are found first. The doctor then must find the location the cancer actually began. The site the cancer spreads to is usually dependent on the type of cancer. Most often, the metastases are discovered in the bones located near the center of the patient's body. The most common site the bone metastases are found in include the spine. Other sites of bone metastases are the skull, ribs, hip bone, upper arm bone (humerus), and upper leg bone (femur).
Symptoms & Complaints
Symptoms include bone pain. The first symptom of bone metastasis is often bone pain. At first, it may come and go. The pain is at its worst at night and often gets better when a person moves. Eventually, it can become constant and activity will make it worse.
If a bone is weakened enough, it will break (bone fracture). For that reason, it is essential that patients notify their doctors if any new pain seems to come from a bone. The breaking of the bone can be prevented with the early detection of bone metastasis.
The spinal cord can be compressed by the growth of cancer in the bones, and the first symptom of spinal cord compression is having difficulty urinating. This is because the control of the bladder is performed by nerves extending from the spinal cord. In addition, constipation can also be a result. Nerves from the spine aid in the movement of the bowels.
Back pain or neck pain are also early symptoms of spinal cord compression. If the pressure on the spinal cord is caused by a tumor, the patient will experience weakness and numbness in the area of the body below the tumor.
It is essential that a spinal cord compression be treated right away in order to prevent the patient from becoming paralyzed. A patient with spinal cord compression may not be able to walking if the legs are affected. If a tumor is causing spinal cord compression in the neck, both the arms and legs might be affected.
Hypercalcemia is high calcium levels in the blood caused by the release of calcium into the blood stream due to the spread of cancer to the bones. This causes problems such as nausea, extreme thirst, constipation and nausea.
Dehydration can also be caused by high levels of calcium because a person produces more urine with this condition which may lead to dehydration. A person may feel very weak and tired and become sleepy or confused. Without prompt treatment of hypercalcemia, it is possible a person could go into a coma.
In order for bone metastasis to take place, tumorous cells have to break off of the primary tumor, enter the bloodstream, attach to the cells of the blood vessels or lymph vessels in order to be transported, and then finally, be able to grow in the new location.
Diagnosis & Tests
Important to the diagnosis of metastatic bone cancer is an accurate and complete description of symptoms as well as the patient's medical history and family history. A physical examination focusing on the most painful areas will also be done by the doctor.
An investigation of the symptoms and signs of bone metastasis is done through medical imaging tests. Imaging Tests usually include:
- Bone scintigraphy (Bone scan)
- Magnetic resonance imaging (MRI)
- Computed tomography (CT) scan
- Positron emission tomography (PET)
Laboratory tests may include:
Treatment & Therapy
When cancer has spread to the bone, there are a number of different treatments that may be available. It is not possible for the treatment to cure a person's bone metastasis. However, in many cases, pain can be relieved, complications can be prevented, and quality of life can be improved.
Either systematic treatments which attack the cancers throughout the body or localized treatment which targets the cancer in the bone directly are used by doctors. The choice of treatment is determined by:
- Both the primary location of the cancer and the type of primary tumor
- Which bones have been invaded by the cancer
- How much damage has been done by the cancer to the bones
- The cancer treatments which a person has previously undergone
- The patient's overall health
A systematic treatment used by doctors to treat bone metastasis is chemotherapy. The type of chemo the doctor will choose to use is the type that has been effective fighting the primary tumor.
Chemotherapy involves the administration of anti-cancer drugs. These drugs will target and impede the growth of the cancer. The drugs are taken by mouth in most cases or they can be administered through a vein by IV. The anti-cancer drugs will shrink the tumors which can result in a reduction of pain.
If the metastasis is weakening the bone, the doctor may prescribe bisphosphonates. Bisphosphonates can be administered every 3 or 4 weeks by IV infusion. This group of drugs will help in the following ways:
- Lessen the bone pain
- Slow down the damage to the bone and reduce the risk of fractures to the bone.
- Reduce high calcium levels in the blood.
Drugs containing radioactive elements are sometimes prescribed. These drugs target cancer cells and are administered intravenously where they travel to the areas of the bone that contain cancer. These drugs are the preferred form of radiotherapy if the cancer has spread to several bones. Doctors may choose to combine the standard radiation therapy and radiopharmaceuticals.
Immunotherapy is a systemic treatment which gives the immune system a boost to fight the cancer cells. With immunotherapy, versions of man-made proteins are also used to kill the cancer cells. It works by simply helping the immune system find as well as effectively kill cancer cells. Some versions of immunotherapy are experimental and available through clinical trials at this time.
If a person has only one or two metastases, the treatment of choice may be radiation therapy. This is because it treats tumors locally and doesn't affect the whole body. The cancer cells in the bone are destroyed or their growth are slowed down by the radiation therapy's high-energy X-rays or particles.
Painful symptoms of bone metastasis can often be relieved with surgery. A weak bone can also be stabilized with surgery preventing it from breaking.
Another option for treatment of only one or two bone tumors is ablation. Ablation is a procedure in which a probe or needle is used to destroy a tumor. This is done by putting the probe or needle into the tumor. Another type of ablation is nerve-end ablation. It is a noninvasive type procedure using MRI technology and ultrasound energy. This procedures relieves pain when it destroys nerve endings in the area surrounding the tumor.
Prevention & Prophylaxis
The goal of this ongoing research is to define the best route, schedule, dose, type of bisphosphonate as well as the overall value in inhibiting bone metastases development.