An estimated 7200 thoracotomies (surgical incision into the chest wall) are performed annually in the UK, most commonly to treat lung cancer. It is considered one of the most painful surgical procedures due to tissue, muscle and nerve damage from the incision, and as the wound heals. The normal breathing motion and nerve injury caused during surgery can result in a high risk of persistent pain for months after surgery. Chronic post-thoracotomy pain (CPTP) is defined as pain that recurs or persists at least two months following the surgery and can occur in up to half of these patients.

There are two commonly used for pain control during thoracotomy: Thoracic Epidural Block (TEB) blocks nerves on both sides of the chest at the spinal cord. It reduces painful nerve signals but may not abolish them completely. Para Vertebral Blockade is done only on the side of surgery and may completely block painful nerve signals from reaching the spinal cord. This total blockade of nerve signals could decrease the likelihood of developing chronic pain and could be uniquely effective in preventing long-term pain.

Over a period of 30 months this trial will be attempting to approach all patients undergoing a thoracotomy at approximately 20 UK hospitals to see if they wish to participate, and to look at the reasons they may not want to participate. We will follow up each participant for a maximum of a year following their surgery.

There is a qualitative intervention embedded within this study to support recruitment.

At the present time, both thoracic epidural block (TEB) and paravertebral blockade (PVB) are routinely used in the UK to provide pain relief for patients undergoing elective open thoracotomy. TEB has long been regarded as the 'gold standard' technique of pain relief for thoracotomy but this has recently been challenged from an overview of the literature on trends and new evidence in the management of acute and chronic post-thoracotomy pain.

In TOPIC 2 the interventional arm will be peri-operative (at or around the time of surgery) pain relief using PVB and the comparator arm will be peri-operative pain relief using TEB. The only pre-operative change to the patient pathway in TOPIC 2 is that the patient will be approached during pre-operative assessment at least 24 hours prior to surgery.

Post-operatively patients will receive analgesia in line with current practice. The trial's hypothesis is that in adult patients undergoing elective open thoracotomy, the use of paravertebral blockade for pain relief at or around the time of surgery reduces both the number of people reporting chronic pain and the persistence of chronic pain at six months by at least 10%, compared with the use of thoracic epidural block. To detect this difference a total of 1026 patients will be recruited from approximately 20 UK hospitals.

Interim analyses of safety and efficacy for presentation to the independent DMC will take place during the study. The committee will meet prior to study commencement to agree the manner and timing of such analyses but this is likely to include the analysis of the primary and major secondary outcomes and full assessment of safety (SAEs) at least at annual intervals. Criteria for stopping or modifying the study based on this information will be ratified by the DMC, but there is also an embedded pilot phase which sets out criteria for assessing whether sufficient progress is made during the first 12 months of recruitment. Failure to open enough sites to recruitment or recruit enough patients from those sites, may be sufficient reason to terminate the trial, or at least re-design some of it to ease these problems.

A randomised controlled trial design has been chosen since this is the acknowledged "gold standard" for evidence based medicine and, because only the patients themselves can say how much pain they are in, patient reported outcomes are appropriate in answering the trial question. Because of the nature of the procedure it is not possible to conceal the surgical team performing the procedure from the allocation but they will not know in advance which of the allocated treatments will be received. There is no reason to believe that patients will have any preconceptions regarding the levels of chronic pain they will experience so the chance of bias is low in this regard.

TOPIC 2 has been designed as a pragmatic trial which collates data during the hospital admission for thoracotomy then, by telephone interview and postal questionnaire at 3, 6 and 12 months. This schedule of events as well as both the type and amount of data collected has been created with substantial input from 2 patient/public representatives.

Since the track record of recruitment to trials involving surgery is not as good as in other areas of medicine, the trial has embedded a qualitative component which will specifically look at the consent process and the reasons for patients either entering or not entering the trial. Patients will therefore initially be asked to consent to the conversation introducing the trial being recorded, and to participate in the main trial. They can choose to participate in just the interview process (conducted in the clinic), just the main trial, neither, or both.

The trial documentation has been prepared in advance of submission to ethics and recruitment is estimated to start in the final quarter of 2018, for 30 months. The first 12 months of recruitment will form an internal pilot phase during which the feasibility of the overall trial will be assessed. Although the primary outcome requires only 6 months followup, patients will be followed up for year to provide a further estimate of how long any differences in pain levels lasts. It will take approximately a further 6 months to analyse the data prior to publication.

Inclusion Criteria:

• Aged ≥18 years
• Elective open thoracotomy
• Able to provide written informed consent
• Willingness to complete study questionnaires up until 12 months post randomisation

Exclusion Criteria:

• Contraindication to TEB or PVB e.g. known allergy to local anaesthetics; infection near the proposed puncture site; coagulation disorders, thoracic spine disorders
• Surgery for chest wall pathology on the side of surgery
• Previous thoracotomy
• Median sternotomy within 90 days

The final data set itself will only be available to the direct TOPIC 2 Trial Team, including the Trial Steering Committee (TSC), in the first instance. It will also be made available upon formal request when the reason for the request is approved by the TSC.