Medical oncologists Leonard Saltz (left) and David Paul Kelsen discuss a patient's treatment.

Medical oncologists Leonard Saltz (left) and David Paul Kelsen discuss a patient's treatment. Two to 5 percent of people with cancer have metastatic tumors of unknown origin.

At Memorial Sloan Kettering, your treatment is managed by a team of doctors, each of whom specializes in using chemotherapy, surgery, radiation therapy, or other therapies to treat cancer of unknown primary origin. This collaborative approach ensures that you will receive the treatment or combination of treatments that will best address your individual condition.

Because cancer of unknown primary origin is by definition a cancer that has spread from a primary site, the disease is already at an advanced stage by the time it has been diagnosed. Although there is no standard treatment for CUP tumors, chemotherapy is usually the primary treatment.

Chemotherapy and Biologic Therapy

Chemotherapy is the most common treatment for patients with cancer of unknown primary origin. Given intravenously or by mouth, chemotherapy destroys cancer cells throughout the body, including areas where they have not yet been found. This approach is used to shrink tumors and relieve symptoms caused by the cancer. In rare cases, chemotherapy can eliminate tumors so that no further treatment is necessary.

When possible, medical oncologists at Memorial Sloan Kettering choose a chemotherapy regimen that is effective in treating the organ or region of the body where they suspect the cancer began. However, even when the primary site or region cannot be identified, we customize each patient’s chemotherapy regimen after determining the type and appearance of the cancer cells, where the cancer has spread, and your overall health.


Surgery is often the treatment of choice for people with a primary tumor that is confined to the organ where it began. But because cancer of unknown primary origin has already spread, surgery is not usually effective. In rare cases, when a CUP tumor is found in only one organ or lymph node, your doctor may recommend surgery. If the cancer is suspected to have begun in the breast, a mastectomy (surgical removal of the breast) may be required to ensure that all of the breast cancer cells have been removed. When surgery is used to treat a cancer of unknown primary origin, it is usually followed by chemotherapy or radiation therapy to eliminate any cancer cells that may remain.

Other Treatments

Radiation therapy is only used to control tumors that cannot be surgically removed or when a cancer of unknown primary origin spreads to the spine and interferes with neurologic function.

Hormone therapy is another option that is used to treat patients whose cancer may have begun in the breast or prostate.