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Other Drugs for a Cancer of Unknown Primary

There are medicines that can be used to prevent problems with bones weakened by cancer metastasis in people who have an unknown primary cancer. Another drug is very helpful for some patients with neuroendocrine tumors. If the tumor releases hormones into the bloodstream, this drug can stop that. It can also stop tumors from growing or (rarely) shrink them.


Bisphosphonates are drugs that are used to help strengthen bones and reduce the risk of fractures 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 reduce the risk of fractures in those that have been weakened by metastatic cancer. 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.

Somatostatin analogs

Octreotide (Sandostatin®) and lanreotide (Samatuline) are drugs that are chemically related to a natural hormone, somatostatin. They are called Somatostatin analogs. This type of drug is very helpful for some patients with well-differentiated 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 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.These drugs are most likely to help treat cancers that show up on somatostatin receptor scintigraphy (OctreoScan).

Peptide receptor radiation therapy (PRRT)

Lutetium Lu-177 dotatate (Lutathera) is a type of radiotherapy, that is made up of two parts: somatostatin analog plus radiation. This drug finds and attaches to cancer cells that has the somotastatin receptor. Once attached, the drug enters the cell, releases radiation, and damages the cancer cell. This form of therapy is most likely to help treat cancers that have the hormone receptor somatostatin, that show upon 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 editors and translators with extensive experience in medical writing.


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Last Revised: May 27, 2024

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