Background Wales, like other UK countries, has relatively poor cancer outcomes. Late diagnosis and a slow referral process are major contributors. General practitioners (GPs) and other care providers working in primary care are often faced with patients presenting with a multitude of non-specific symptoms that could be cancer. Safety netting can be used to manage diagnostic uncertainty by ensuring patients with vague symptoms are appropriately monitored. The ThinkCancer! Workshop is an educational behaviour change intervention aimed at the whole general medical practice team, designed to improve primary care approaches to ensure timely diagnosis of cancer. The workshop will consist of teaching and awareness sessions, appointment of a Safety Netting Champion and the development of a bespoke Safety Netting Plan. This study aims to assess the feasibility of the ThinkCancer! Intervention for a future definitive randomised controlled trial, in terms of recruitment, randomisation, retention, acceptability, adherence and barriers to the intervention.

Methods The ThinkCancer! study is a randomised, multisite feasibility trial, with an embedded process evaluation and economic evaluation. Twenty-three to 30 general medical practices will be recruited across Wales, randomised in a ratio of 2:1 of intervention versus control who will follow usual care. The workshop will be delivered by a GP educator, and will be adapted iteratively throughout the trial period. Baseline practice characteristics will be collected via questionnaire. We will also collect Primary Care Interval (PCI), Two Week Wait (2WW) referral rate, conversion rate and detection rate at baseline and six months post-randomisation. Participant feedback, researcher reflective notes and economic costings will be collected following each workshop. A process evaluation will assess implementation using an adapted Normalisation Measure Development (NoMAD) questionnaire and qualitative interviews. An economic feasibility analysis will inform a future economic evaluation.

Discussion This study will allow us to test and further develop a novel evidenced-based complex intervention aimed at general practice teams to expedite the diagnosis of cancer in primary care. The results from this feasibility study will inform the future design of a full-scale definitive phase III trial.

Inclusion Criteria:

• Any practices in Wales are eligible for inclusion.

Exclusion Criteria:

• As we intend to include a broad group of general medical practices, there are no formal exclusion criteria.

As determining feasibility is the main objective of this study, the eligibility criteria remain broad in order to allow for inclusion of a range of practices, which will aid the intervention refinement and allow for a better understanding on what is feasible in all types of practices and why some practices may not take part.