What is bone metastasis? A secondary malignant growth, bone metastasis occurs when cancer cells break away from a distant, primary tumor site and spread (metastasize) to bone. It is important to clarify the meaning of bone metastasis; it is not the same as bone cancer, which is a tumor that originates in bone and is relatively uncommon. On the other hand, any cancer can potentially spread to a bone. In fact, it is estimated that more than 330,000 people are currently living with bone metastasis. The most common bone metastasis sites include the breast, prostate, lung, kidney and thyroid. Additionally, lymphoma (Hodgkin and non-Hodgkin) and multiple myeloma often metastasize to a bone.
Symptoms of bone metastasis
Individuals who have been diagnosed with any type of cancer should pay close attention to possible symptoms of metastasis to bone and promptly discuss them with a physician. It is important to understand that bone metastasis symptoms can occur for many reasons. Therefore, only a physician can pinpoint the source and provide an accurate diagnosis.
Some possible bone metastasis symptoms include:
Usually, localized pain around the site of the metastasis is the first noticeable sign of cancer metastasis to bone. Common sites for bone metastasis include the spine, upper leg bone (femur), the hip bone (pelvis), upper arm bone (humerus), ribs and skull.
The characteristics of the pain can vary depending on the location of the metastasis. For instance, cancer that has spread to the spine may cause back pain that worsens with bed rest. Cancer that has spread to a long bone in an arm or leg may cause pain that worsens with movement and improves with rest.
"These metastatic diseases should be treated more like trauma. They can have distracting pain and not realize there is another impending fracture that they need fixed as soon as possible to mobilize."- Dr. David Joyce, Sarcoma Program
Normally, a bone will crack or break if too much force is applied, which can result from a fall or direct blow. However, with bone metastasis, fractures can result from even mild stress applied during daily activities. Bones with metastasis can weaken and increase the risk of fractures in two ways: First, it can destroy healthy bone tissue, and second, it can release chemicals that can affect the formation of new bone tissue and weaken newly formed bones.
Bone metastasis patients should take extra care to protect their frail bones. Toward that end, a physician may recommend stopping or changing certain activities. A physician can also identify an impending fracture, which is a bone that is about to break and provide treatment to reinforce it.
Spinal nerve compression
If cancer spreads to a spinal bone, a growing tumor may press on the spinal cord or a spinal nerve root. This can cause back pain and make walking painful and difficult. Other symptoms of spinal nerve compression include muscle weakness, numbness and tingling sensations in the arms or legs. In severe cases, bladder or bowel incontinence may develop; either may be a sign of a medical emergency that warrants immediate treatment in a hospital ER.
Bone metastasis can accelerate the rate at which bone tissue breaks down. This, in turn, can elevate the level of calcium in the blood, which can cause weakness, fatigue, excessive thirst and frequent urination.
Other symptoms of metastasis to bone
Bone metastasis can affect the bone marrow, particularly if a patient receives extensive chemotherapy or radiation therapy. This, in turn, can impact blood cell counts. A drop in the level of red blood cells can lead to anemia and symptoms such as fatigue and weakness. A drop in the level of white blood cells can lead to frequent infections. Finally, a drop in the level of platelets may cause excessive bleeding.
Causes of bone metastasis
Cancer occurs when healthy cells undergo abnormal changes that cause them to grow and divide uncontrollably. The abnormal cells then build up, bind together and form tumors. Sometimes, cancerous cells break away from a tumor and travel throughout the body. Although the shed cells may die off, they can potentially invade distant tissues and create metastatic tumors.
Scientists are still working to better understand why some tumors metastasize and others do not. Studies show that up to 70% of patients with a certain type of cancer, such as advanced breast cancer and advanced prostate cancer, ultimately develop bone metastasis.
Diagnosis of bone metastasis
The diagnostic process for bone metastasis may include:
A physician may order blood or urine testing to check for bone turnover markers. For instance, when abnormal bone tissue is being formed by cancer cells, a high level of alkaline phosphatase may be present. Hypercalcemia can also be detected through bloodwork.
Bone damage and lesions often appear in X-ray images. However, a physician may order a computerized axial tomography (CAT) scan for more precise information. During a CAT scan, the imaging machine rotates around the patient’s body to take multiple images from various angles. A computer then processes the resulting images to create a single, three-dimensional image.
If a patient has bone pain, but a bone scan produces a normal result, a physician may order a magnetic resonance imaging (MRI) scan, which can produce detailed images of soft tissues, such as bone marrow, which may reveal a tumor.
Bone marrow aspiration and biopsy
A bone biopsy involves the removal of a small sample of bone tissue. A pathologist then analyzes the sample under a microscope to check for signs of bone metastasis.
Bone metastasis treatment
When determining how to treat bone metastasis, a physician will consider many factors, including the patient’s age, symptoms and overall health, as well as the site, size and extent of the bone metastasis and the types of treatment the patient has had in the past.
Bone metastasis treatment may include:
Several drugs and drug combinations may be prescribed to improve comfort. Sometimes, medication is used along with surgery, radiation therapy or another treatment.
Radiation therapy involves the use of high-energy rays, which can be targeted directly at a bone metastasis site to destroy cancerous cells or interfere with their growth and development. By shrinking a tumor, radiation therapy can relieve bone pain and reduce the risk of fractures.
In some cases, orthopedic surgery is considered to restore the function of a damaged bone. The type of procedure recommended will depend upon the location and size of the bone metastasis tumor. Usually, surgery involves removing all or part of a tumor, then stabilizing the bone to prevent fractures. If a fracture or impending fracture is present, the surgery may include placing metal plates, rods, screws, wires and/or pins to secure the bone.
Bisphosphonates are a class of medications that can be effective for treating bone metastases in some patients with breast cancer or myeloma. Usually, the medications are administered intravenously in conjunction with other treatments.
Bone metastasis survival rate
Is bone metastasis curable? No, but appropriate treatment can significantly improve a patient’s outcome and quality of life. How long can you live with bone metastasis? The life expectancy with bone metastasis can vary depending on many unique factors, including the patient’s age and overall health and the type and location of the cancer. Some people live for many years after receiving a diagnosis of bone metastasis.
If you would like to learn more about bone metastasis, you are welcome to consult with a specialist in the Bone Metastasis Clinic in the Sarcoma Program at Moffitt Cancer Center. Our extensive services include evaluating and treating bone lesions of unknown primary origin, bone fractures and impending bone fractures. To request an appointment, call 1-888-663-3488 or complete our new patient registration form online. We provide every new patient with rapid access to a cancer expert within one day, which is faster than any other cancer hospital in the nation.