Targeted therapy for cancer of unknown primary

Last medical review:

Targeted therapy uses drugs to target specific molecules (such as proteins) on cancer cells or inside them. These molecules help send signals that tell cells to grow or divide. By targeting these molecules, the drugs stop the growth and spread of cancer cells and limit harm to normal cells. Targeted therapy may also be called molecular targeted therapy.

A few people with cancer of unknown primary (CUP) have targeted therapy. If you have targeted therapy, your healthcare team will use what they know about the cancer and about your health to plan the drugs, doses and schedules.

You may have targeted therapy to:

  • kill cancer cells
  • relieve pain or control the symptoms of advanced CUP (called palliative therapy)

Targeted therapy by where the CUP may have started

You may be offered targeted therapy if your healthcare team thinks the CUP started in the breast or if you have a neuroendocrine CUP.

Researchers are still looking at how effective certain targeted therapy drugs might be against other types of CUP.

Targeted therapy for CUP that may have started in the breast

Targeted therapy may be offered when the healthcare team thinks that the breast is the primary site of CUP in lymph nodes under the arm. The targeted therapy drugs used are the same as those given for breast cancer.

Find out more about targeted therapy for breast cancer.

Targeted therapy for neuroendocrine CUP

Targeted therapy may be used to treat well-differentiated neuroendocrine CUP. The targeted therapy drugs that are used are sunitinib (Sutent) and everolimus (Afinitor).

Sunitinib is a type of targeted therapy drug called a tyrosine kinase inhibitor. Tyrosine kinases are proteins on the surface of cells that send signals to help cells grow and divide. Sunitinib blocks the action of different tyrosine kinases, which helps slow or stop cancer cells from growing and spreading. Sunitinib also works as an anti-angiogenesis drug, which means it prevents tumours from developing new blood vessels.

Everolimus is a drug called an mTOR inhibitor. Mammalian target of rapamycin (mTOR) is a protein that controls cell growth and reproduction. Everolimus blocks the action of mTOR, which can stop the growth of the cancer.

Side effects of targeted therapy

Side effects of targeted therapy will depend mainly on the type of drug or combination of drugs, the dose, how it’s given and your overall health. Tell your healthcare team if you have side effects that you think are from targeted therapy. The sooner you tell them of any problems, the sooner they can suggest ways to help you deal with them.

Targeted therapy drugs used for CUP that may have started in the breast can cause these side effects:

Sunitinib may cause these side effects:

Everolimus may cause these side effects:

Find out more about targeted therapy

Find out more about targeted therapy. To make the decisions that are right for you, ask your healthcare team questions about targeted therapy.

Details on specific drugs change regularly. Find out more about sources of drug information and where to get details on specific drugs.

Expert review and references

  • Tien Le , MD, FRCSC, DABOG
  • American Cancer Society . Treating a Cancer of Unknown Primary . 2018 :
  • American Society of Clinical Oncology (ASCO). Unknown Primary: Types of Treatment. 2021:
  • Fizazi K, Greco FA, Pavlidis N, Daugaard G, Oien K, Pentheroudakis G . Cancers of unknown primary site: ESMO clinical practice guidelines for diagnosis, treatment and follow-up . Annals of Oncology . 2015 : 26(Supplement 5):v133–v138 .
  • PDQ Adult Treatment Editorial Board. Carcinoma of Unknown Primary Treatment (PDQ®) – Health Professional Version. Bethesda, MD: National Cancer Institute; 2018:
  • Yentz S, Bhave M, Cobain E, Baker L. Cancer of Unknown Primary. DeVita VT Jr., Lawrence TS, Rosenberg SA, eds. DeVita, Hellman, and Rosenberg's Cancer: Principles & Practice of Oncology. 11th ed. Philadelphia, PA: Wolters Kluwer; 2019: Kindle version, ch 108, .

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