When breast cancer metastasizes, one of the primary locations it spreads to is the bones. Although other research shows that it can also spread to the lungs, liver or brain. This phenomenon, known as bone metastases or “bone mets,” occurs in approximately 70 percent of women with metastatic breast cancer, according to a study.
While it is possible for breast cancer to metastasize to any bone in the body, the most common sites include the spine, hip bone, upper leg and arm bones, ribs, and skull, as noted by the American Cancer Society (ACS).
The exact reason why breast cancer cells prefer to settle in the bones remains unclear. However, experts suggest that the bone marrow’s rich blood supply and abundant nutrients create a conducive environment for cancer growth.
“Our bone marrow may provide an excellent environment for cancer growth because of its rich blood supply and many available nurtients,” says Steven Isakoff, MD, PhD, a medical oncologist and director of breast cancer clinical research at Mass General Cancer Center in Boston.
Typically, bone pain is the first indication that breast cancer has spread to the bones. However, bone metastases can sometimes present with little or no symptoms. In these cases, routine scans or fractures resulting from minor falls or injuries might reveal the presence of cancerous lesions in the bones.
Alissa Huston Porter, MD, a breast cancer oncologist and an associate professor of medicine at the James P. Wilmot Cancer Institute at the University of Rochester in New York says, “A fracture is one of the worst case scenarios, and one we try to avoid.”
Although these secondary bone cancers are not curable, there are advanced treatments available to reduce complications, alleviate symptoms, and prolong life, says the review.
Furthermore, early detection and treatment of bone metastases can be critical in preventing future problems, according to the ACS.
Early detection of bone metastases can be challenging. However, new research suggests that potential of using biomarkers for early detection. Although these tests re not yet widely available, ongoing investigation into blood-based detection methods offer hope for the future.
Signs to Watch Out For
Dr. Huston stresses, “Most aches and pains aren’t cancer. But it’s important to keep an open and honest dialogue with your doctor about any unusual or persistent discomfort you may be having. He or she can determine if getting images is appropriate to rule out bone metastasis.”
Here are the symptoms of bone metastasis to watch for:
Bone Pain
Pain is the most common symptom of bone metastasis. Initially, the pain may come and go, worsen at night, and improve with movement. As the condition progresses, the pain may become constant and intensify during physical activity, according to the ACS.
It is crucial to inform your healthcare provider about any new, unexplained pain that does not resolve with rest. Early detection and treatment of bone metastases can help prevent factures and other complications.
Broken Bones
Bone metastases can weaken and destabilize bones, making them more susceptible to fractures. The most common fracture sites are the spine and the long bones of the arms and legs, such as the humerus and femur.
Fractures can occur from falls, trauma, or even everyday activities if the bone is significantly weakened. Sudden, severe bone pain should prompt immediate medical attention, as it can be a sign of a fracture.
Spinal Cord Compression
When cancer spreads to the bones of the spine, it can compress the spinal cord, leading to symptoms such as weakness in the legs, numbness in the belly or legs, difficulty urinating, and constipation.
Band-like pain around the torso is another reported symptom. Immediate medical attention is necessary if these symptoms occur, as untreated spinal cord compression can result in paralysis.
Extreme Thirst, Loss of Appetite, and Sluggishness
These symptoms may indicate hypercalcemia, a condition characterized by high calcium levels in the blood. Hypercalcemia can result from breast cancer and bone metastases releasing calcium into the bloodstream. Other symptoms include bone pain, abdominal cramping, constipation, mood changes, and kidney stones.
Left untreated, hypercalcemia can lead to coma and abnormal heart rhythms. “Hypercalcemia is treated with several approaches,” says Dr. Isakoff, including IV fluids and bisphosphonates. Monitoring calcium levels during treatment is essential to avoid excessively low calcium levels.
“Hypercalcemia is treated with several approaches,” says Dr. Isakoff, including IV fluids and bisphosphonates (a medication used to treat bone mets). “But it’s important to monitor the calcium level when treating with these medications to make sure the calcium level doesn’t go too low,” Dr. Isakoff adds.
Anne Peled, MD, a breast cancer surgeon in San Francisco says, “With a history of cancer, it’s probably best to let your oncologist know if you have any new medical symptoms that last more than a week, and certainly much sooner with any severe symptoms.”
If you report any of these symptoms to your doctor, they may conduct a thorough physical exam and blood tests, according to the Mayo Clinic. Based on the results and the severity or location of the bone pain, your doctor may also order imaging tests like an X-ray, PET scan, CT scan, bone scan, or MRI for further evaluation. In some cases, a tissue biopsy may be performed to confirm the diagnosis.
How Bone Metastases Are Treated
Oncologists possess a variety of tools to alleviate the pain and discomfort of bone metastases while also treating the underlying cancer.
Systemic Cancer Treatment
“When breast cancer spreads to the bones, it is generally treated with the same therapies used to treat breast cancer that has spread to other parts of the body,” says Dr. Isakoff.
Per the Mayo Clinic, systemic treatment for bone mets may include:
1. Chemotherapy – According to Dr. Isakoff, chemotherapy can be effective in reducing cancer pain, although side effects such as hair loss, nausea, and fatigue may occur.
- Endocrine Therapy – As per a review, this involves estrogen-blocking treatments, which can slow bone metastasis by disrupting the cycle of growth between breast cancer cells and bone cancer cells. Common side effects of endocrine therapy include hot flashes, decreased libido, and vaginal dryness or irritation, says ACS.
Bone-Modifying Medications
Bisphosphonates like zoledronic acid are used to prevent bone loss, reduce pain, and prevent hypercalcemia. Dr. Isakoff shares, “Studies show these medications can reduce the risk of skeletal events, including fractures and spinal cord compression, by 25 to 40 percent.”
However, long-term use may cause side effects such as kidney dysfunction and jaw bone issues. Reducing the frequency of bisphosphonate administration can minimize side effects while maintaining efficacy.
Denosumab, another medication that prevents bone breakdown, has been found effective in delaying bone fractures from cancer metastasis, says a study of 247 people published in BMC Cancer.
As per the prescribing label of denosumab, side effects of denosumab may include jaw bone breakdown, atypical femur fractures, musculoskeletal pain, skin conditions, and low calcium levels.
However, a meta-analysis published in Frontiers in Oncology states that more research is required to better understand how the medication works exactly.
Surgery
According to Mayo Clinic, surgery may be recommended to remove tumors or stabilize bones to prevent or manage fractures.
Dr. Peled says, “[However], unlike medications and radiation therapy, surgery is really not used to treat or remove bone metastases. It’s primarily used to manage impending bone fractures or fractures that have already happened as a result of the metastases.”
Dr. Isakoff agrees, saying “In this situation, surgery can be highly effective to reduce pain and prevent or repair a fracture.”
Surgical interventions can be highly effective in reducing pain and preventing or repairing fractures. Spinal fractures may be treated with vertebroplasty, an outpatient procedure where bone cement is injected into a collapsed vertebra to rebuild it and alleviate back pain.
According to one review, decreased mobility is the most common side effect of surgery. The surgeon must reconstruct areas damaged by the cancer, making rehabilitation challenging.
Radiation
Radiation therapy may be utilized to prevent fractures and treat spinal cord compression, alleviating symptoms of pain or numbness, according to Dr. Huston Porter. One type of radiation, called radiopharmaceuticals, is administered through an IV and contains radioactive material that targets the bones.
However, internal radiation can damage bone marrow, leading to decreased blood cell counts.
The most common side effect of external beam radiation is skin irritation, though other side effects depend on the specific treatment area. For instance, radiation to a joint can cause damage, resulting in decreased range of motion and mobility.
Pain Medications
In most cases, providers begin pain control with NSAIDs (nonsteroidal anti-inflammatory drugs) such as ibuprofen, says Dr. Isakoff, as these medications block the production of prostaglandins, which are substances the body releases in response to illness or injury.
“If additional pain medications are needed, opioid narcotics in conjunction with ibuprofen can be effective, and sometimes steroid anti-inflammatory medications can be added,” says Dr. Isakoff.
He adds that if your pain is concentrated in a specific area, limited radiation therapy can be highly effective and may help reduce the need for higher doses of other medications.
Opioids, such as oxycodone (Oxycontin/Roxicodone), can effectively reduce pain over a short period. However, they may cause side effects like drowsiness and constipation and can be addictive if misused, according to MedicinePlus.
Research on opioid use for chronic pain (lasting beyond three months or past the healing period) is limited, so their long-term effectiveness is largely unknown, according to one study.
Other effective methods for managing pain and discomfort from bone metastases include using hot and cold compresses, practicing relaxation techniques such as meditation, engaging in physical therapy or yoga, and participating in other gentle forms of exercise, according to a review.
Consult your healthcare team about programs that can help you stay safely active.
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