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Cancer of unknown primary

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Survival statistics for cancer of unknown primary

Survival statistics for cancer of unknown primary (CUP) are very general estimates and must be interpreted very carefully. Because these statistics are based on the experience of groups of people, they cannot be used to predict a particular person’s chances of survival.

There are many different ways to measure and report cancer survival statistics. Your doctor can explain the statistics for CUP and what they mean to you.

Relative survival

Relative survival looks at how likely people with cancer are to survive after their diagnosis compared to people in the general population who do not have cancer, but who share similar characteristics (such as age and sex).

In Canada, a separate 5-year relative survival statistic is not reported for cancer of unknown primary but is included in the general category other, ill-defined and unknown sites of cancer. This broad category includes similar cancers that are grouped and reported together. This statistic does not necessarily reflect the actual survival for the individual cancers within the group. The 5-year relative survival for all other, ill-defined and unknown sites of cancer is 28%. This means that, on average, people diagnosed with other, ill-defined and unknown primary sites are 28% as likely to live 5 years after their diagnosis as people in the general population. However, this is a very broad grouping of cancers and it is difficult to say what the 5-year relative survival is specifically for CUP or certain CUP subtypes.

Factors influencing survival

CUP includes many different cancer types, which makes it hard to provide accurate survival statistics for these cancers as a group. In general, people with CUP have a poor prognosis. They are often diagnosed with an advanced stage of cancer because it has already spread (metastasized). Also, it can be difficult to know what treatment will be the most effective since the exact type of primary cancer may not be known. Survival varies in people with CUP depending on the subtype of CUP, their performance statusperformance statusThe measure of how well a person is able to perform ordinary tasks and carry out daily activities., how widespread the cancer is and how they respond to treatment.

Survival statistics for CUP are often reported as median survival. Median survival is the period of time (usually months or years) at which half the people with CUP are still alive and the other half are not. Median survival in people with CUP is generally 3–4 months. The median survival may be longer if people have favourable prognostic factors.

  • Less than 25% of people with CUP will be alive 1 year after they are diagnosed.
  • Less than 10% of people with CUP will be alive 5 years after they are diagnosed.

Questions about survival

People with cancer should talk to their doctor about their prognosis. Prognosis depends on many factors, including:

  • a person’s medical history
  • type of cancer
  • stage
  • characteristics of the cancer
  • treatments chosen
  • response to treatment

Only a doctor familiar with these factors can put all of this information together with survival statistics to arrive at a prognosis.


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