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Carcinoma of unknown primary (CUP) is a disease in which cancer (malignant) cells are found somewhere in the body, but the place where they first started growing (the origin or primary site) cannot be found. This occurs in about 2%-4% of cancer patients.
Actually, CUP can be described as a group of different types of cancer all of which have become known by the place or places in the body where the cancer has spread (metastasized) from another part of the body. Because all of these diseases are not alike, chance of recovery (prognosis) and choice of treatment may be different for each patient.
If CUP is suspected, a doctor will order several tests, one of which may be a biopsy. This means a small piece of tissue is cut from the tumor and looked at under a microscope. The doctor may also do a complete history and physical examination, and order chest x-rays along with blood, urine, and stool tests. A cancer can be called CUP when the doctor cannot tell from the test results where the cancer began.
The pattern of how CUP has spread may also give the doctor information to help determine where it started. For example, lung metastases are more common when cancer begins above the diaphragm (the thin muscle under the lungs that helps the breathing process). Most large studies have shown that CUP often starts in the lungs or pancreas. Less often, it may start in the colon, rectum, breast, or prostate.
An important part of trying to find out where the cancer started is to see how the cancer cells look under a microscope (histology). Other special tests may also be done that help the doctor find out where the cancer started and choose the best type of treatment.
When cancer is diagnosed, more tests are usually done to find out if cancer cells have spread to other parts of the body. This is called staging. But, when CUP is diagnosed, the number and type of tests done may be different for each patient. The treatment options in this summary are based on whether the cancer has just been found (newly diagnosed) or the cancer has come back after it has been treated (recurrent).
The treatment options are also based on where the cancer is found or what it looks like. A doctor may find that the cancer fits into one of the following groups:
Many different treatments are used either alone or in combination to treat CUP. Some of the treatments that are used are:
Radiation therapy uses x-rays or other high-energy rays to kill cancer cells and shrink tumors. Radiation may be used alone or before or after surgery.
Chemotherapy uses drugs to kill cancer cells. Chemotherapy may be taken by mouth or it may be put into the body by a needle in a vein or muscle. Chemotherapy is called a systemic treatment because the drugs enter the bloodstream, travel through the body, and can kill cancer cells throughout the body. Chemotherapy may be used alone or after surgery. Therapy given after an operation when there are no cancer cells that can be seen is called adjuvant therapy.
Hormone therapy is used to stop the hormones in the body that help cancer cells grow. This may be done by using drugs that change the way hormones work or by surgery that takes out organs that make hormones, such as the testicles (orchiectomy).
Treatment of CUP depends on where the doctor thinks the cancer started, what the cancer cells look like under a microscope, and other factors. Surgery and tests may be done to find where the cancer started.
Standard treatment may be considered because of its effectiveness in patients in past studies, or participation in a clinical trial may be considered. Not all patients are cured with standard therapy and some standard treatments may have more side effects than are desired. For these reasons, clinical trials are designed to find better ways to treat cancer patients and are based on the most up-to-date information. Clinical trials are ongoing in most parts of the country for CUP. To learn more about clinical trials, call the Cancer Information Service at 1-800-4-CANCER (1-800-422-6237); TTY at 1-800-332-8615.
2. Radiation therapy.
3. Radiation therapy followed by surgery.
4. Neck surgery (radical neck dissection).
5. Neck surgery followed by radiation therapy.
If the cancer is a poorly differentiated carcinoma (the cancer cells look very different than normal cells), the treatment will probably be chemotherapy. Surgery or radiotherapy has also been used for patients with neuroendocrine (nervous system and hormonal system) cancer.
If the cancer is peritoneal adenocarcinomatosis (the tumor is in the lining inside the abdomen), the treatment will probably be chemotherapy.
If the cancer is an isolated axillary nodal metastasis, it is likely that the cancer started in the lung or breast. If female, a mammogram (an x-ray picture of the breast) will be used to check for breast cancer. After tests to check for lung and breast cancer, the treatment may be one of the following:
2. Treatment as described above plus chemotherapy that is used for breast cancer.
2. Groin surgery (superficial groin dissection).
3. Surgery to remove some of the tumor (biopsy) with or without radiation therapy, surgery to remove the lymph nodes, or chemotherapy.
If there is cancer in several different areas of the body and the doctor thinks that the origin of the cancer is one for which there is standard systemic therapy, then that therapy should be given. The following are examples:
2. Chemotherapy or hormone therapy for breast cancer.
3. Chemotherapy for ovarian cancer.
To learn more about carcinoma of unknown primary, call the National
Cancer Institute's Cancer Information Service at 1-800-4-CANCER (1-800-422-6237);
TTY at 1-800-332-8615. By dialing this toll-free number, trained information
specialists can answer your questions.
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