Chemotherapy for a Cancer of Unknown Primary

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

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.

Chemo may be the main treatment for cancers that are 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 cancer of unknown primary (CUP) that is an adenocarcinoma or a poorly differentiated carcinoma, a number of chemo combinations may be used, including:

• Carboplatin plus paclitaxel (Taxol^®)
• 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 plus 5-fluorouracil
• Cisplatin plus gemcitabine
• Oxaliplatin (Eloxatin^®) plus 5-fluorouracil and leucovorin (folinic acid)

Neuroendocrine cancers (carcinomas)

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

Patients who have CUP and are found to have well-differentiated neuroendocrine cancer on a biopsy are treated with drugs combinations such as:

• Octreotide (Mycapssa) or Lanreotide (Somatuline): a type of drug called a somatostatin analog
• Lutetium Lu-177 dotatate (Lutathera): a type of drug called a radiolabeled somatostatin analog
• Capecitabine
• Temozolomide 

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 what side effects you can expect from 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.