Want the key stats in the sections on this page as a document? or looking for a stats report of the in-depth stats? Use the print function at the bottom of any Cancer Stats page Share this page > Print or your browser options to print or save.
Cancer of unknown primary statistics
New cases of cancer of unknown primary, 2014-2016 average, UK
Deaths from cancer of unknown primary, 2016, UK
- There are around 8,800 new cancer of unknown primary cases in the UK every year, that's 24 every day (2014-2016).
- Cancer of unknown primary is the 15th most common cancer in the UK, accounting for 2% of all new cancer cases (2016).
- In females in the UK, cancer of unknown primary is the 11th most common cancer, with around 4,600 new cases in 2016.
- In males in the UK, cancer of unknown primary is the 14th most common cancer, with around 4,300 new cases in 2016.
- Incidence rates for cancer of unknown primary in the UK are highest in people aged 90+ (2013-2015).
- Since the early 1990s, cancer of unknown primary incidence rates have decreased by more than half (52%) in the UK. Rates in males have decreased by almost three-fifths (56%), and rates in females have decreased by half (50%).
- Over the last decade, cancer of unknown primary incidence rates have decreased by almost two-fifths (38%) in the UK. Rates in males have decreased by almost two-fifths (39%), and rates in females have decreased by almost two-fifths (37%).
- Most cancers of unknown primary occur in the respiratory and digestive organs.
- Cancer of unknown primary in England is more common in people living in the most deprived areas.
- An estimated 12,500 people who had previously been diagnosed with cancer of unknown primary (CUP) were alive in the UK at the end of 2010.
- There are around 9,800 cancer of unknown primary deaths in the UK every year, that's 27 every day (2014-2016).
- Cancer of unknown primary is the 5th most common cause of cancer death in the UK, accounting for 6% of all cancer deaths (2016).
- In males in the UK, cancer of unknown primary is the 6th most common cause of cancer death, with around 4,400 deaths in 2016.
- In females in the UK, cancer of unknown primary is the 4th most common cause of cancer death, with around 5,000 deaths in 2016.
- Mortality rates for cancer of unknown primary in the UK are highest in people aged 90+ (2014-2016).
- Since the early 1970s, cancer of unknown primary mortality rates have increased by almost nine-tenths (88%) in the UK. Rates in males have increased by more than three-quarters (77%), and rates in females have increased by almost two times (97%).
- Over the last decade, cancer of unknown primary mortality rates have decreased by more than a third (35%) in the UK. Rates in males have decreased by almost two-fifths (37%), and rates in females have decreased by a third (33%).
- Cancer of unknown primary deaths in England are more common in females living in the most deprived areas.
The latest statistics available for cancer of unknown primary in the UK are; incidence 2015 and mortality 2014. Reliable survival data for the UK is currently not available.
European Age-Standardised Rates were calculated using the 1976 European Standard Population (ESP) unless otherwise stated as calculated with ESP2013. ASRs calculated with ESP2013 are not comparable with ASRs calculated with ESP1976.
Cancer of unknown primary (CUP) is an inexact term, making it hard to represent accurately. Patients are recorded as having CUP if the primary site of the malignancy cannot be established or the tumour has been registered without specification of site. Capturing and reporting the incidence of CUP cases can be difficult. In some patients the primary site or the tumour type cannot be determined, even after extensive investigations. In others, patients presenting with wide-spread metastases without an obvious primary site may be too ill to undergo invasive tests or have cancer at such an advanced stage that further investigations would no longer aid their diagnosis or treatment. Both scenarios will lead to patients being registered as CUP. However, some patients, initially diagnosed with CUP, may subsequently have their primary site determined (either during the diagnostic/treatment process or at post-mortem) and will thus no longer be registered and counted as CUP. Finally, a few cases may be misclassified and end up registered as CUP when the clinical or pathological information transmitted to the Cancer Registry is insufficient; for example if the primary site of the malignancy is not indicated on the notes or reports. Due to this unspecific classification the National Institute for Health and Clinical Excellence (NICE) issued a guideline which stated that the majority of CUP can be covered by the ICD codes ICD-10 C77-C801, so the statistics presented on these pages are our best current understanding of the incidence of CUP.
Mortality statistics for CUP are further complicated by the fact that they are compiled separately from cancer registration, at the Office for National Statistics (ONS), and are based solely on the clinical statement of causes of death on the death certificate. Depending on circumstances the clinician completing the death certificate may not be aware of, or have access to, the deceased patient's primary cancer diagnosis or might only state the metastatic spread of the cancer as the cause of death. As ONS have to rely on the death certificate this can lead to higher mortality statistics for more vague ICD-10 codes, which includes the metastatic and unknown primary codes defined as CUP. Thus, CUP mortality figures are, in part, thought to be higher than CUP incidence figures because a cause of death statement of, for example, 'cancer' or 'metastatic liver disease' would result in a CUP mortality code even if the patient was not originally diagnosed with CUP.
Patient Experience data is for adult patients in England with a primary diagnosis of cancer, who were in active treatment between September and November 2013 and who completed a survey in 2014.
Deprivation gradient statistics were calculated using incidence data for three time periods: 1996-2000, 2001-2005 and 2006-2010 and for mortality for two time periods: 2002-2006 and 2007-2011. The 1997-2001 mortality data were only used for the all cancers combined group as this time period includes the change in coding from ICD-9 to ICD-10. The deprivation quintiles were calculated using the Income domain scores from the Index of Multiple Deprivation (IMD) from the following years: 2004, 2007 and 2010. Full details on the data and methodology can be found in the Cancer by Deprivation in England NCIN report.
You are welcome to reuse this Cancer Research UK content for your own work.
Credit us as authors by referencing Cancer Research UK as the primary source. Suggested styles are:
Web content: Cancer Research UK, full URL of the page, Accessed [month] [year].
Publications: Cancer Research UK ([year of publication]), Name of publication, Cancer Research UK.
Graphics (when reused unaltered): Credit: Cancer Research UK.
Graphics (when recreated with differences): Based on a graphic created by Cancer Research UK.
When Cancer Research UK material is used for commercial reasons, we encourage a donation to our life-saving research.
Send a cheque payable to Cancer Research UK to: Cancer Research UK, Angel Building, 407 St John Street, London, EC1V 4AD or
We are grateful to the many organisations across the UK which collect, analyse, and share the data which we use, and to the patients and public who consent for their data to be used. Find out more about the sources which are essential for our statistics.