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Other Drugs for a Cancer of Unknown Primary


Bisphosphonates are drugs that are used to help strengthen and reduce the risk of fractures in bones that have been weakened by metastatic cancer. Examples include pamidronate (Aredia®), zoledronic acid (Zometa®), and clodronate (Bonefo®). They are given in a vein (intravenously; IV) once a month.

Bisphosphonates can have side effects, including flu-like symptoms and bone pain. They can also cause kidney problems, so people with kidney problems can’t use them. A rare but very distressing side effect of intravenous bisphosphonates is damage (osteonecrosis) in the jaw bones (ONJ). It can be triggered by having a tooth removed while getting treated with the bisphosphonate. ONJ often appears as an open sore in the jaw that won’t heal. It can lead to loss of teeth or infections of the jaw bone. Doctors don’t know why this happens or how to treat it, other than to stop the bisphosphonate drug. Good oral hygiene by flossing, brushing, making sure that dentures fit properly, and having regular dental check-ups may help prevent this. Most doctors recommend that patients have a dental check-up and have any tooth or jaw problems treated before they start taking a bisphosphonate.


Like bisphosphonates, denosumab (Prolia®, Xgeva®) is a drug that can be used to strengthen bones and lower the risk of fractures in bones weakened by cancer spread. This drug is injected under the skin, once a month to treat cancer that has spread to bone.

Side effects include low levels of calcium and phosphate and ONJ. This drug does not cause kidney damage, so it is safe to give to people with kidney problems.


Octreotide (Sandostatin®) is an agent chemically related to a natural hormone, somatostatin. It’s very helpful for some patients with neuroendocrine tumors. If the tumor releases hormones into the bloodstream (which is rare in the poorly differentiated tumors that cause cancer of unknown primary), this drug can stop the hormone release. It can also cause tumors to stop growing or (rarely) to shrink. This drug is available as a short-acting version injected 2 to 4 times a day, or as a long-acting injection that needs to be given only once a month. A similar drug, lanreotide (Somatuline®), is also injected once a month. These drugs are most likely to help treat cancers that show up on somatostatin receptor scintigraphy (OctreoScan).

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

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Last Revised: March 9, 2018

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