In the United States, breast cancer is the most common cancer in women (excluding skin cancer) and the second most common cause of death from cancer in women. Breast cancer in men is much less common, accounting for less than 1% of all breast cancer diagnoses. Sometimes, breast cancer spreads outside of the breast in a process called metastasis. One of the most common distant places breast cancer can spread is the bone. When breast cancer has spread to the bone, people may experience significant pain and loss of movement. To manage these problems, your doctor may use medications, surgery, or radiation therapy.

Bone-modifying drugs are used to help strengthen the bone and reduce pain and fractures (bone breaks) from bone metastases. These drugs can also lessen the need for surgery or radiation therapy to manage bone problems, so they are often used for patients with bone metastases from breast cancer. However, these drugs have not been shown to extend life or slow the growth of breast cancer. There are two different classes of bone-modifying drugs and both help stop the bone from breaking down. One class, called bisphosphonates, is used for bone metastases and includes pamidronate and zoledronic acid. The drug denosumab is an antibody made in a laboratory that also helps stop bone breakdown.

A possible condition associated with bone-modifying drugs is osteonecrosis of the jaw. It is an uncommon but serious condition. The symptoms of osteonecrosis of the jaw include pain, swelling, and infection of the jaw; loose teeth; and exposed bone.

The side effects of pamidronate and zoledronic acid include flu-like symptoms that may occur with the first few doses and kidney problems. It's important for your health care team to do blood tests to check your kidney function before each dose. Denosumab is not specifically associated with kidney problems, but can cause hypocalcemia (low levels of calcium in the blood). Your doctor may recommend calcium and vitamin D supplements to reduce the risk of hypocalcemia if you are taking any bone-modifying drug for breast cancer that has spread to the bone. The dose and how often you should take calcium and vitamin D supplements is different for each person and should be discussed with your doctor.