Chemotherapy for cancer of unknown primary

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Chemotherapy uses drugs to destroy cancer cells. These drugs target rapidly dividing cells throughout the whole body. This means that chemotherapy kills cancer cells, but it can also damage healthy cells.

With most types of chemotherapy, the drugs travel through the blood to reach and destroy cancer cells all over the body, including cells that may have broken away from the primary tumour. This is described as systemic therapy.

Most people with cancer of unknown primary (CUP) have chemotherapy. For some people, the healthcare team may decide that chemotherapy isn't the best treatment option because they are in poor health or the type of CUP is not likely to respond to chemotherapy.

If you have chemotherapy, your healthcare team will use what they know about the cancer and about your health to plan the drugs, doses and schedules.

Chemotherapy is given for different reasons. You may have chemotherapy to:

  • destroy cancer cells in the body
  • destroy cancer cells left behind after surgery and reduce the risk that the cancer will come back (recur) (called adjuvant chemotherapy)
  • relieve pain or control the symptoms of advanced CUP (called palliative chemotherapy)

Chemotherapy and radiation therapy may be given during the same period to treat squamous cell CUP that is found in lymph nodes in the neck or the groin. This is called chemoradiation.

Chemotherapy drugs used for CUP

Different combinations of chemotherapy drugs are used for different types of CUP. Usually 2 or more drugs are used. Most combinations include at least one of the following:

  • a platinum drug – either cisplatin or carboplatin
  • a taxane drug – either paclitaxel or docetaxel

Other drugs that may be used include:

  • gemcitabine
  • etoposide (Vepesid)
  • 5-fluorouracil (also called 5-FU or fluorouracil)
  • streptozocin (Zanosar) – for neuroendocrine CUP

If your healthcare team has an idea of where the cancer started, you will be offered chemotherapy drugs that treat that specific type of cancer. These drugs may be different from what is listed here.

Side effects of chemotherapy

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

Some common side effects of chemotherapy drugs used for CUP are:

Find out more about chemotherapy

Find out more about chemotherapy and side effects of chemotherapy. To make the decisions that are right for you, ask your healthcare team questions about chemotherapy.

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:
  • National Comprehensive Cancer Network . NCCN Clinical Practice Guidelines in Oncology: Occult Primary (Cancer of Unknown Primary) Version 1.2023 . 2022 .
  • 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, .
  • Tan WW . Medscape Reference: Metastatic Cancer With Unknown Primary Site . 2022 :

Medical disclaimer

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