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Chemotherapy for a Cancer of Unknown Primary

Chemotherapy (chemo) is the use of drugs to treat cancer. Often, these drugs are injected into a vein (IV) or taken by mouth. They enter the bloodstream and reach throughout the body, making this treatment potentially useful for cancers that have spread beyond the organ they started in. Because chemo reaches all parts of the body, it can sometimes be useful for cancers of unknown primary, as it may help kill cancer cells in areas where they haven’t been detected.

Chemo can be used in a number of situations for cancer of unknown primary (CUP). If your doctor recommends chemo, it’s important that you understand what the goals of your treatment are.

Chemo may be the main treatment for cancers that are clearly advanced and are unlikely to be helped by local treatments such as surgery or radiation therapy. In some cases, it may be very effective in making tumors shrink or even go away altogether. In other cases, chemo may be used to try to relieve symptoms caused by the cancer and may be able to help people live longer.

For cancers that appear to have been removed completely with surgery or radiation, chemo may be added to try to kill any remaining cancer cells in the body.

Chemo drugs are often given in combinations, which are more likely to be effective than giving a single drug alone. Which chemo drugs are used depends on the type of cancer.

Adenocarcinoma and poorly differentiated carcinoma

For a CUP that is an adenocarcinoma or a poorly differentiated carcinoma, a number of chemo combinations may be used, including:

  • Carboplatin plus paclitaxel (Taxol®), with or without etoposide (VP-16)
  • Carboplatin plus docetaxel (Taxotere®)
  • Cisplatin plus gemcitabine (Gemzar®)
  • Cisplatin plus docetaxel
  • Gemcitabine plus docetaxel
  • Irinotecan (Camptosar®) plus carboplatin
  • Irinotecan plus gemcitabine
  • Oxaliplatin (Eloxatin®) plus 5-fluorouracil and leucovorin (folinic acid)
  • Oxaliplatin plus capecitabine (Xeloda®)

Squamous cell cancer (carcinoma)

If chemotherapy is to be used for a CUP that is a squamous cell cancer, the options include:

  • Cisplatin or carboplatin plus a taxane (paclitaxel or docetaxel)
  • Cisplatin, docetaxel, and 5-fluorouracil (5-FU)
  • Cisplatin plus 5-fluorouracil
  • Cisplatin plus gemcitabine
  • Oxaliplatin (Eloxatin®) plus 5-fluorouracil and leucovorin (folinic acid)

Neuroendocrine cancers (carcinomas)

Neuroendocrine carcinomas that are poorly differentiated are often treated with the same chemo as is used for small cell cancer of the lung: a platinum drug (cisplatin or carboplatin) and etoposide.

Well-differentiated neuroendocrine cancers are not often the cause of CUP, but may present with liver metastasis and an occult primary. These patients are treated like patients with well-differentiated carcinoid tumor, with drugs combinations such as:

  • Doxorubicin (Adriamycin®) and streptozocin
  • Temozolomide plus capecitabine
  • Cisplatin or carboplatin plus etoposide
  • Carboplatin plus paclitaxel and etoposide

More information about the treatment of well-differentiated neuroendocrine cancers can be found in Gastrointestinal Carcinoid Tumors, Lung Carcinoid Tumor, and Pancreatic Cancer.

Possible side effects of chemotherapy

Chemo drugs can cause side effects, depending on the specific drugs used, their doses, and how long treatment lasts.

Common side effects of chemo include:

  • Hair loss
  • Mouth sores
  • Loss of appetite
  • Diarrhea
  • Nausea and vomiting
  • Increased chance of infections (from a shortage of white blood cells)
  • Problems with bruising or bleeding (from a shortage of blood platelets)
  • Fatigue or shortness of breath (from low red blood cell counts)

Along with the risks above, some chemo drugs can cause other side effects.

Ask your health care team about what side effects you can expect based on the specific drugs you will get. Be sure to tell your doctor or nurse if you do have side effects, as there are often ways to help with them. For example, drugs can be given to help prevent or reduce nausea and vomiting.

More information about chemotherapy

For more general information about how chemotherapy is used to treat cancer, see Chemotherapy.

To learn about some of the side effects listed here and how to manage them, see Managing Cancer-related Side Effects.

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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