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The HIDDEN trial aimed to investigate the prevalence of deep venous thrombosis in patients with advanced cancer.


The HIDDEN trial aimed to investigate the prevalence of deep venous thrombosis in patients with advanced cancer, aiming to determine prevalence and predictors of femoral deep vein thrombosis in patients admitted to specialist palliative care units (SPCUs). The trial challenged, and changed, existing international thromboprophylaxis guidance in this population. Results were published in The Lancet.

Extending investigation

This trial seeks to extend the investigation in the same group of patients, in the admitted hospital setting. It is suspected that patients in this group will receive thromboprophylactically, where evidence for the efficacy or need of this treatment is not robust.  Potential issues with both under-treatment (if thromboprophylaxis is not followed) may be less impactful than over-treatment where a small sub-group may experience acute bleeding episodes. The HIDDEN2 trial will seek to identify whether current guidelines are supported by findings of this observational study.

Study design

While the prevalence of asymptomatic venous thromboembolisms (VTEs) is felt to be around 5%; the prevalence in the SPCU setting was found to be 30%. Therefore, it is expected that for the group of patients admitted to hospital, who will have a longer expected survival than those in SPCU, the prevalence will be between 5 and 30%. At 17% prevalence, 217 patients will give a 95% Confidence Interval; with an expected 8% drop out approximately 232 patients will be recruited. Approximately, 1,000 patients per year at both AB and UHW have been identified as potentially eligible. A 1-year recruitment phase is proposed, though it is expected that recruitment will take approximately 9 months, providing some room for potential delays in trial set-up.


HIDDEN2 opened to recruitment at Aneurin Bevan UHB on 4th May 2022, and is actively recruiting.

Key facts

Start date 1 Oct 2021
End date 1 Mar 2023
Grant value £188,000
  • Recruiting

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