What is Bone Metastasis?
Bone metastasis occurs when cancer cells spread from their original site to a bone. Nearly all types of cancer can spread (metastasize) to the bones. But some types of cancer are particularly likely to spread to bone, including breast cancer and prostate cancer.
Bone metastasis can occur in any bone but more commonly occurs in the pelvis and spine. Bone metastasis may be the first sign that you have cancer, or bone metastasis may occur years after cancer treatment.
Bone metastasis can cause pain and broken bones. With rare exceptions, cancer that has spread to the bones can’t be cured. Treatments can help reduce pain and other symptoms of bone metastases.
How Cancer Spreads to Bone
“Bone metastases can be a difficult concept to grasp,” says Julie Fasano, MD, a medical oncologist with Memorial Sloan-Kettering Cancer Center’s Commack Facility in Long Island, N.Y. Although it usually shows up within two to three years of diagnosis, it can appear many years later, she says. Sometimes, it doesn’t cause any symptoms.
How does it happen? Metastasis can occur when cancer cells break away from the primary tumor, where the cancer began. The cells may then enter the bloodstream or lymph system and travel to the bone marrow. “The matrix of the bone marrow secretes cytokines,” Fasano says. These proteins may attract cancer cells.
Cancer cells can remain hidden and inactive in bone for a long time. This means they can evade treatment. At some point, however, the cells may begin to multiply and grow new blood vessels to obtain oxygen and food. This allows a tumor or tumors to form.
Scientists are just beginning to understand what happens in the bone to prompt this process, Fasano says. Once metastasis begins, there may be a “vicious, self-perpetuating cycle.” The release of cytokines may attract yet more cancer cells to the bone marrow, and this may help cancer cells survive.
Symptoms of Bone Metastasis
- Pain. The most common symptom of MBD is pain. Patients may have pain in the spine, pelvis, or extremities because the bone has been weakened by the tumor.
- Fractures. Weakened bones break more easily. A fracture from a minor injury is another possible sign of MBD.
- Anemia. The most common sites of spread spine, pelvis, ribs, skull, upper arm, and long bones of the leg correspond to areas of bone marrow that produce high levels of red blood cells, the cells responsible for carrying oxygen to tissues in the body. Anemia (decreased red blood cell production) is a common blood abnormality in patients with MBD.
A cancer patient who experiences any pain, especially in the back, legs, and arms, should notify his or her doctor immediately. Pain that occurs without activity (i.e., walking or lifting an object) is particularly concerning.
Signs and symptoms of Bone Metastasis include:
- Bone pain
- Broken bones
- Urinary incontinence
- Bowel incontinence
- Weakness in the legs
- High levels of calcium in the blood (hypercalcemia), which can cause nausea, vomiting and confusion
Treatment of Bone Metastasis
- Bisphosphonates. Bisphosphonates are drugs that slow the bone damage caused by metastases. They are used to decrease the risk of bone complications like fractures and to lower abnormally high blood calcium levels. Studies suggest that treatment with bisphosphonates can also reduce the bone pain associated with bone metastasis.
- Radiation therapy. Radiation is useful in relieving pain and controlling the growth of tumor cells in the area of the bone metastasis. It may be used to prevent a fracture or as a treatment for spinal cord compression.
- Surgery. Surgical treatment for bone metastases is done to prevent or to treat a bone fracture. It usually involves removing the tumor and stabilizing the bone to prevent a fracture. Metal rods, plates, screws, wires, nails or pins may be surgically inserted to strengthen or provide structure to the bone damaged by metastasis.
- Other therapies. Other treatments for bone metastases and their symptoms include physical therapy, and drug and nondrug approaches to control pain. Effective treatment of the primary cancer is the best way to manage bone metastases. In addition to the cancer treatment, there are a variety of treatment options available for bone metastasis. These include chemotherapy, hormonal therapies, targeted therapies and immunotherapies.
