Thrombocytosis - an underused risk marker of cancer in primary care

South West PeninsulaCancer
Start Date: 1 Jan 2014


The UK has a poor record in cancer outcomes, much of which is blamed on delays in diagnosis. Many initiatives have been established to help primary care identify and investigate patients with possible cancer. One factor which has received little attention is a raised platelet count (thrombocytosis). Our team has identified this as being relevant in lung, colon, ovary, oesophago-gastric, bladder and pancreas cancers. Together, these six cancer sites suggest that the risk of an underlying cancer in a patient with thrombocytosis exceeds 4% and may be as high as 10%. Such a figure would make a very important contribution to cancer diagnosis: a contribution that is currently completely absent from current diagnostic practice.

Research objective

How useful is thrombocytosis in predicting an underlying cancer?

In all studies the NIHR CLAHRC research team has conducted previously, they have started with a cancer and worked backwards towards clinical features including thrombocytosis. In this study, the team will start with general practice patients with thrombocytosis, and identify a) which cancers are associated, b) how strong the association is – in terms of a percentage risk, and c) which level of platelet count is optimal for recommending cancer investigation (incorporating the patient’s age and sex).

The study will use 50,000 patients from the CPRD, 40,000 with a raised platelet count, and 10,000 without. We will link this dataset to the national cancer registries to confirm cancer diagnoses. We will perform a cohort study, with sub-analyses by age, sex and platelet count. Our power calculation has shown that 50,000 patients will provide sufficient cases to give very reliable results.

Main outcome measure

The incidence of cancer in the one year following a raised platelet count.

The team is extremely experienced in both CPRD and cancer diagnostic studies, containing a statistician, professors of diagnostic medicine and a practising haematologist. Furthermore, the research group into which this study will be embedded has an extremely strong record in clinical implementation of research findings.

Professor Willie Hamilton