- In 2011, around 9,800 people were diagnosed with cancer of unknown primary in the UK, that’s 27 people every day.
- Cancer of unknown primary can occur at any age, but more than half of cases are diagnosed in people aged 75 and over.
- Cancer of unknown primary accounts for around 3% of all cancers in the UK.
- Cancer of unknown primary incidence rates in the UK have decreased by 39% in males and 34% in females, respectively, over the last decade. Most of the decline is due to more cancer cases having their primary site specified (and so not being registered as CUP), which reflects improvements in diagnostic methods, and better registration practices.
Cancer of unknown primary statistics
New cases of cancer of unknown primary, 2011, UK
Deaths from cancer of unknown primary, 2012, UK
- Around 10,625 people died from cancer of unknown primary in 2012 in the UK, that’s 29 people every day.
- Six in ten deaths from cancer of unknown primary are in people aged 75 and over.
- Over the last decade, cancer of unknown primary mortality rates in the UK have decreased by 37% for men and 32% for women.
The latest statistics available for cancer of unknown primary in the UK are; incidence 2011 and mortality 2011. Reliable survival data for the UK is currently not available.
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.
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