What is bone metastasis? Bone metastasis occurs when cancer cells break away from an original tumor, spread throughout the body, and invade a bone. The bones are among the most common cancer metastasis sites, along with the lungs and the liver.
There is often confusion surrounding the meaning of bone metastasis. Contrary to popular belief, bone metastasis is not bone cancer. For instance, breast cancer that spreads to the bone is still considered breast cancer, not bone cancer. The distinction is important because primary bone tumors such as osteosarcomas—which originate in bone—are treated differently than bone metastases, which originate elsewhere in the body.
What types of cancer can spread to bone?
Nearly all types of tumors can spread, but those most likely to metastasize to bone include:
- Breast cancer
- Prostate cancer
- Lung cancer
- Kidney cancer
- Thyroid cancer
- Lymphoma (Hodgkin and non-Hodgkin)
- Multiple myeloma
"They may not realize that these patients could be at risk for a fracture. Our goal is to find out if these patients are at risk for a fracture and help them before that happens."- Dr. David Joyce, Sarcoma Program
Likewise, cancer can invade virtually any bone, but the most common sites for bone metastases are the:
- Hip bone (pelvis)
- Upper leg bone (femur)
- Upper arm bone (humerus)
What are the symptoms of bone metastasis?
The most common sign of cancer metastasis to bone is a sudden, new pain, which can be similar to the discomfort caused by arthritis or a muscle strain. The pain may come and go at first, then gradually become constant, even during rest. As cancer progresses, frequent fractures (broken bones) may occur.
In addition to bone pain and fractures, some possible skeletal-related events (SREs) associated with bone cancer metastasis include spinal nerve compression and excessive blood calcium (hypercalcemia) due to bone breakdown.
Spinal nerve compression
The signs of spinal nerve compression include:
- Neck or back pain
- Muscle weakness
- Numbness and tingling sensations in the arms or legs
- Difficult walking
- Bladder or bowel incontinence (a medical emergency)
After evaluating the symptoms, a physician can determine how to treat bone metastasis. For example, if a bone tumor is pressing on the spinal cord or a spinal nerve root, prompt bone metastasis treatment can help relieve the pain and other symptoms. Treatment may include radiation therapy, often started within 12 to 24 hours. Additionally, steroids or corticosteroids may be administered to reduce inflammation in the spine.
The signs of hypercalcemia include:
- Muscle weakness
- Muscle and joint aches
- Frequent urination
- Excessive thirst
- Loss of appetite
If left untreated, hypercalcemia can lead to coma and kidney failure, so it is important to recognize the early signs. In general, treatment involves the administration of intravenous (IV) fluids to protect the kidneys, and administering medications such as bisphosphonate drugs to quickly lower the calcium level in the blood. Once the blood calcium is restored to a normal level, cancer treatment can help keep it under control.
How is bone metastasis diagnosed?
If bone metastasis is suspected based on the symptoms, a physician may order one or more imaging studies, such as a:
- Bone scan
- Computed tomography (CT) scan
- Positron emission tomography (PET) scan
- Magnetic resonance imaging (MRI) scan
A physician may also order blood testing to measure the blood calcium level or check for tumor markers. A high calcium level may indicate that cancer has spread to the bones, and an elevated high tumor marker level may indicate widespread bone metastasis.
If a bone lesion is present, a physician may order a biopsy, which involves removing a cell sample so that a pathologist can evaluate it. The pathologist can identify cancer cells by viewing the sample under a microscope.
What are the causes of bone metastasis?
The spread of cancer to bone is a complex process, and researchers in the general medical community are still working to gain a better understanding of it. Essentially, cancer cells invade healthy tissues surrounding the original tumor, then penetrate the walls of nearby blood vessels or lymph vessels. Once the cancer cells enter the bloodstream or the lymphatic system, they can travel throughout the body.
After reaching small vessels in a distant area of the body, the cancer cells can penetrate the vessel walls and migrate into surrounding tissues, such as bones, then multiply and form small tumors.
Scientists do not yet know why some tumors spread or why the cancer cells sometimes invade bones instead of other tissues. As a result, many studies related to this topic are currently underway. For instance, the acclaimed research team at Moffitt Cancer Center is currently investigating how cancer cells metastasize to bone and how those cells interact with the bone environment in order to grow.
What is the bone metastasis prognosis?
Individuals who have been diagnosed with cancer in the past should pay close attention to possible symptoms of metastasis to bone and bring them to the attention of a physician immediately. Is bone metastasis curable? No. But an accurate diagnosis and prompt treatment can help prevent fractures and other complications of bone metastasis, such as SREs. This approach can lead to the best possible outcome and quality of life.
How long can you live with bone metastasis? The life expectancy with bone metastasis can vary widely. For instance, many factors can affect the bone metastasis survival rate, such as the patient’s age and overall health and the type and location of the cancer. Some people live for many years after learning they have bone metastasis.
If you are concerned about bone metastasis symptoms, you are welcome to consult with a specialist in the Bone Metastasis Clinic in the Sarcoma Program at Moffitt Cancer Center, where you can benefit from the latest innovations in treatment for bone cancer metastasis. To request an appointment, complete our new patient registration form online or call 1-888-663-3488. 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.