Treatment options for certain kinds of cancer of unknown primary

The types of treatment used for a cancer of unknown primary (CUP) depend on several factors, such as the size and place of the cancer, the results of lab tests, and how likely it is to be a certain type of cancer. Your overall health and how well you can withstand treatment matter, too. Of course, if the place where the cancer started can be found during testing, the cancer would no longer be an unknown primary and would be treated like that type of cancer.

Squamous cell cancer in lymph nodes in the neck

Often these cancers began somewhere in the mouth, throat, or larynx. These are often first treated with surgery to remove the lymph nodes and often some nearby tissue. There are different types of neck surgery (called neck dissection) in which lymph nodes or even muscles, nerves, and veins are removed. Radiation treatment and/or chemotherapy (chemo) may be used, as well. To learn more about the treatment of these types of cancer, please see our documents on Oral Cavity and Oropharyngeal Cancer and Laryngeal and Hypopharyngeal Cancer.

Cancer in lymph nodes under the arm

Because most cancer in the lymph nodes under the arm (the axillary nodes) in women is from breast cancer, the treatment is often the same as for women with breast cancer that has spread to these nodes. To learn more, see our document Breast Cancer.

For men with cancer in lymph nodes under the arm, spread from the lung is much more likely. Treatment options will most likely involve surgery with radiation and/or chemo. But in most cases the doctor will watch to see how the lymph nodes respond to chemo first.

Cancer in groin lymph nodes

If the place where these cancers started can be found, surgery is often the main treatment. If more than one lymph node is found to have cancer, radiation treatment and/or chemo may be used along with surgery.

Women with cancer throughout the pelvic area

Unless tests point to something else, the cause is most likely ovarian, fallopian tube, or primary peritoneal cancer. These are all treated in much the same way. Surgery will often be done to remove the uterus, both ovaries, both fallopian tubes, and as much of the cancer as possible. After surgery, chemo will be given for 6 to 8 months. For more information, see our document Ovarian Cancer.

Cancer in the back of the belly (retroperitoneum) or the space between the lungs (mediastinum)

If tests have ruled out lymphoma, then the most likely cause (especially in younger men) is a germ cell tumor. Treatment would likely be chemo. Even cancers in these places that do not have lab results for germ cell tumors often respond to the type of chemo used for testicular germ cell tumors. More information about the treatment of germ cell tumors can be found in our documents, Testicular Cancer and Ovarian Cancer.

If the cancer is in the mediastinum in an older patient it may be treated as a non-small cell lung cancer.

Melanoma in lymph nodes only

Once a CUP has been found to be melanoma (a skin cancer) then it is no longer a true CUP. But tests may take several days, and during that time the cancer is still called a CUP. Treatment involves removing the involved lymph nodes. Radiation may be given as well. Sometimes a drug called interferon is given to slow the return of the cancer. For more information, see our document Melanoma Skin Cancer.

Cancer in places like the bone or liver

Most cases of CUP fall into this group. Often the cancer is in the bones, lung, or liver. If lab tests show that it is not a cancer of the breast, prostate, thyroid, or lymphoma (all of which often respond well to specific treatments), many of the remaining patients are treated with chemo to try to shrink the tumor and reduce symptoms.

Sometimes chemo can be quite helpful. About 15% of patients treated with strong chemo will have a complete response, and in some of these cases the cancer stays away for years.

Patients in poor health who would not be able to withstand the side effects of strong chemo are sometimes given lower doses or drugs that cause fewer side effects. But we don’t know how much this really helps. Another option is to focus on relieving symptoms as they happen. Many patients with cancer spread to bones are helped by treatment with bisphosphonates or denosumab (discussed in the “Other drugs for cancer of unknown primary” section). These drugs can help strengthen bones weakened by cancer. This may prevent breaks (fractures) and reduce pain.

Some neuroendocrine cancers may respond to treatment with octreotide (Sandostatin). This drug may be able to slow or stop growth for some time.

More details about treatments for cancers that have spread can be found in our document Advanced Cancer.