Breast Cancer Metastasis to Bone

Breast cancer is the most common site of origin of metastatic deposits in the skeleton.  As many of half of all pathological fractures are due to breast cancer.  Although the prognosis for patients with breast cancer that has spread to the bone vas poor in the past, nowadays these patients are living much longer and feeling much better due to dramatic improvements in medical and surgical treatments of this problem.

One of the most exiting new developments is a class of drugs knows as bisphosphonates (Aredia, Fosamax, Didronel, and others).  These drugs have the ability to block the progression of tumor cells in the bone, leading to dramatically fewer bone lesions and bone fractures in patients with bone cancer who take them.  Bisphosphonates may even stop the spread of breast cancer to other organs, such as the liver or lungs, but the reason for this is unknown.  In the bones, the osteoclast cell is stimulated by the cancer to break down and resorb bone matrix and calcium, leading to pain and fractures.  These drugs block the osteoclast cells and keep the bones strong.  I recommend all patients with breast cancer take these drugs to protect their bones.  Even if mild or moderate side effects develop, such as joint aches or stomach upset, these should be tolerated because protection of the bones is more important.  In my clinical experience, patients who go off these drugs because of mild side effects have experienced rapid development of bone metastasis and required surgery.  Always consult your doctor about these treatments.

Pain is the most common presenting symptom.  Pathological fracture rarely occurs without a history of a few weeks or months of increasingly severe pain.  In some cases the patient has tried to ignore or deny the symptoms.  Sometimes a painful bone lesion is thought to be a "muscle pull" or a "sprain" and strong pain medicines are prescribed, allowing the patient to continue to tolerate very severe pain before the true nature of the problem is discovered. Systemic symptoms may also occur, such as hypercalcemia.

Breast cancer metastasis most commonly affects the spine, ribs, pelvis, and proximal long bones.
The lesions can often be blastic but may also appear purely lytic, with poor margination, no matrix and cortical destruction.  When you see a woman over age 40 with a history of breast cancer and multiple bone lesions, think metastatic breast cancer.  However, just the fact that the patient had cancer does not prove that the lesion you see in the bone is from that cancer.  Do not bypass a careful history, physical exam, and complete workup just because the patient gives a history of breast cancer.  Other lesions such as compression fractures of the spine and cysts from osteoarthritis can appear to be tumors. Also remember that primary bone sarcomas such as osteosarcoma and chondrosarcoma can occur in an adult female patient. 

The average survival after the diagnosis of a breast cancer metastasis to bone has dramatically improved to about 24 - 36 months.  The bisphosphonate class of drugs is likely to lead to more improvements in survival. 

Breast cancer is the most common cause of pathological fractures, and orthopaedic surgeons who treat this disease should keep their approach to treatment up to date with current surgical practice.  There is virtually no role for curative surgery.  Orthopedic stabilization of weakened bones should be done promptly, before fractures can occur.  Delay in treatment is normally associated with increased risk of complications or a less favorable outcome.   Since survival may be prolonged, surgical reconstructions should be carefully done and designed to last.  Patients with extensive or advanced disease should still receive complete treatment according to their wishes and reasonable medical principles.  Orthopaedic stabilization of actual or impending pathological fractures should not be withheld unless the patient cannot tolerate anaesthesia or would definitely not be benefited by surgery. The pain relief from stabilization of damaged bones may warrant surgical treatment even if the patient cannot enjoy a functional benefit, such as increased walking ability.