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Cancer Of Unknown Primary (CUP)

When a person is diagnosed with cancer that has spread within the body (metastatic cancer) the primary site – the place in the body where the cancer started –  is not always obvious. Finding the genetic origin of the cancer is important to define the best treatment. When the origin of the cancer is not identified with confidence, after initial tests, this is described as Cancer of Unknown Primary or CUP.

In the UK about 8,600 people are diagnosed with CUP each year – that is about 24 every day. CUP is the 15th most frequent cancer diagnosis and the 6th commonest cause of cancer death in the UK. (Since 2007 CUP incidence and mortality rates have decreased by about a third in the UK.) Broken down by gender CUP is the 11th most common cancer for women and the 15th most common for men [CRUK data 2024]. The number of people diagnosed with CUP each year in the UK would fill about 20 jumbo jets; yet most people have never heard of CUP and find it hard to believe that in this scientific age the cause of the cancer, and its spread, can remain unknown.

For many of those diagnosed initially with an undefined or uncertain metastatic cancer the origin of the cancer will be found through further tests. When the primary site/ tumour of origin remains truly unknown the cancer can be contained with treatment, but life expectancy is limited.

A cancer diagnosis is frightening for patient, family and friends. Not to know where this strange, invasive, disease has originated in the body is a double blow. CUP patients face unique psychological and social concerns.  We exist to offer information and support to CUP patients, their families and friends; whilst raising awareness of this problem to stimulate action that will improve treatment.

Please note: We are no longer a registered charity and we are not accepting donations; but we are supporting CUP research through The Christie Hospital and continuing to maintain this site as a source of information for patients, carers, clinicians and researchers. More here

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