Prognosis and survival for cancer of unknown primary

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A prognosis is the doctor’s best estimate of how cancer will affect someone and how it will respond to treatment. Survival is the percentage of people with a disease who are alive at some point in time after their diagnosis. Prognosis and survival depend on many factors.

The doctor will look at certain aspects of the cancer and characteristics of the person (such as their overall health and sex). These aspects are called prognostic factors. The doctor will also look at predictive factors, which influence how a cancer will respond to a certain treatment and how likely it is that the cancer will come back after it was treated.

Prognostic and predictive factors are often discussed together. They both play a part in deciding on a prognosis and a treatment plan just for you. Only a doctor familiar with your medical history, the type and characteristics of the cancer, the treatments chosen and the response to treatment can put all of this information together with survival statistics to arrive at a prognosis and chances of survival.

The following are prognostic and predictive factors for cancer of unknown primary (CUP).

Favourable-risk or poor-risk CUP

The healthcare team will describe CUP as favourable risk or poor risk based on:

  • where the cancer is found in the body
  • the type of cancer they think it is based on biopsy results
  • how likely the cancer is to respond to treatment
  • the sex you were assigned at birth

Favourable-risk CUPs have a better prognosis. Poor-risk CUPs have a poorer prognosis.

Favourable-risk CUPs include:

  • neuroendocrine carcinoma
  • adenocarcinoma in the lymph nodes under the arm in people who were assigned female at birth
  • adenocarcinoma in the peritoneal cavity in people who were assigned female at birth
  • squamous cell carcinoma in the lymph nodes in the neck (called cervical lymph nodes) or in the groin (called inguinal lymph nodes)
  • poorly differentiated carcinoma in the middle (or midline) of the body
  • CUP in a bone in people who have a high prostate-specific antigen (PSA) level
  • CUP that is likely to have started in the colon
  • CUP that is in only one lymph node or one organ

Poor-risk CUPs include:

  • adenocarcinoma in the liver and other organs
  • adenocarcinoma found in a buildup of fluid in the abdomen (called malignant ascites)
  • CUP in several different places in the brain
  • CUP in several parts of the lungs or the lining of the lungs
  • CUP in a bone in people who do not have a high PSA level
  • CUP in the adrenal glands

Performance status

Performance status is a measure of how well a person can do ordinary tasks and carry out daily activities (such as bathing, dressing or walking). Different performance status scales are used, but in general the more active you are, the better your performance status.

A person diagnosed with CUP who has a good performance status has a better prognosis than someone who has a poor performance status.

Lactate dehydrogenase (LDH) levels

People diagnosed with CUP who have normal lactate dehydrogenase (LDH) levels in their blood have a better prognosis than people with high levels of LDH.


The healthcare team will consider the sex you were assigned at birth when estimating prognosis. People with CUP who were assigned female at birth tend to have a better prognosis than people with CUP who were assigned male at birth.


People younger than 65 years of age have a better prognosis.

Expert review and references

  • Tien Le , MD, FRCSC, DABOG
  • American Cancer Society . Cancer of Unknown Primary Early Detection, Diagnosis, and Staging . 2018 :
  • PDQ Adult Treatment Editorial Board. Carcinoma of Unknown Primary Treatment (PDQ®) – Health Professional Version. Bethesda, MD: National Cancer Institute; 2018:
  • National Comprehensive Cancer Network . NCCN Clinical Practice Guidelines in Oncology: Occult Primary (Cancer of Unknown Primary) Version 1.2023 . 2022 .
  • Yentz S, Bhave M, Cobain E, Baker L. Cancer of Unknown Primary. DeVita VT Jr., Lawrence TS, Rosenberg SA, eds. DeVita, Hellman, and Rosenberg's Cancer: Principles & Practice of Oncology. 11th ed. Philadelphia, PA: Wolters Kluwer; 2019: Kindle version, ch 108, .
  • Tan WW . Medscape Reference: Metastatic Cancer With Unknown Primary Site . 2022 :
  • Fizazi K, Greco FA, Pavlidis N, Daugaard G, Oien K, Pentheroudakis G . Cancers of unknown primary site: ESMO clinical practice guidelines for diagnosis, treatment and follow-up . Annals of Oncology . 2015 : 26(Supplement 5):v133–v138 .

Survival statistics for cancer of unknown primary

Survival statistics for cancer of unknown primary (CUP) are very general estimates. Survival is difficult to estimate for CUP because it includes many types of cancer.

Medical disclaimer

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