Español
PDFs by language
Our 24/7 cancer helpline provides information and answers for people dealing with cancer. We can connect you with trained cancer information specialists who will answer questions about a cancer diagnosis and provide guidance and a compassionate ear.
Chat live online
Select the Live Chat button at the bottom of the page
Call us at 1-800-227-2345
Available any time of day or night
Our highly trained specialists are available 24/7 via phone and on weekdays can assist through online chat. We connect patients, caregivers, and family members with essential services and resources at every step of their cancer journey. Ask us how you can get involved and support the fight against cancer. Some of the topics we can assist with include:
For medical questions, we encourage you to review our information with your doctor.
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.
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:
If chemotherapy is to be used for a CUP that is a squamous cell cancer, the options include:
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:
More information about the treatment of well-differentiated neuroendocrine cancers can be found in Gastrointestinal Carcinoid Tumors, Lung Carcinoid Tumor, and Pancreatic Cancer.
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:
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.
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 editors and translators with extensive experience in medical writing.
Bochtler T, Löffler H, Krämer A. Diagnosis and management of metastatic neoplasms with unknown primary. Semin Diagn Pathol. 2018 May;35(3):199-206. doi: 10.1053/j.semdp.2017.11.013. Epub 2017 Nov 26. PMID: 29203116.
Greco FA, Hainsworth JD. Carcinoma of Unknown Primary In: DeVita VT, Lawrence TS, Rosenberg SA, eds. DeVita, Hellman, and Rosenberg’s Cancer: Principles and Practice of Oncology. 10th ed. Philadelphia, PA: Lippincott Williams & Wilkins 2015: 1719-1736.
Lee MS, Sanoff HK. Cancer of unknown primary. BMJ. 2020 Dec 7;371:m4050. doi: 10.1136/bmj.m4050. PMID: 33288500.
National Cancer Institute. Physician Data Query (PDQ). Cancer of Unknown Primary Treatment. 05/6/2024. Accessed at: https://www.cancer.gov/types/unknown-primary/hp/unknown-primary-treatment-pdq on May 20, 2024.
National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Occult Primary. v.2.2024. Accessed at https://www.nccn.org on May 20, 2024.
Tomuleasa C, Zaharie F, Muresan MS, Pop L, Fekete Z, Dima D, Frinc I, Trifa A, Berce C, Jurj A, Berindan-Neagoe I, Zdrenghea M. How to diagnose and treat a cancer of unknown primary site. J Gastrointestin Liver Dis. 2017 Mar;26(1):69-79. doi: 10.15403/jgld.2014.1121.261.haz.
Varadhachary GR, Lenzi R, Raber MN, Abbruzzese JL. Carcinoma of Unknown Primary In: Neiderhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE, eds. Abeloff’s Clinical Oncology. 5th ed. Philadelphia, PA. Elsevier: 2014:1792-1803.
Last Revised: May 27, 2024
American Cancer Society medical information is copyrighted material. For reprint requests, please see our Content Usage Policy.
Sign up to stay up-to-date with news, valuable information, and ways to get involved with the American Cancer Society.
If this was helpful, donate to help fund patient support services, research, and cancer content updates.