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Although surgical resection has been considered the only curative option for colorectal liver metastases, thermal ablation has recently been suggested as an alternative curative treatment. There have been no adequately powered trials comparing surgery with thermal ablation.Main objective - to compare the clinical effectiveness and cost-effectiveness of thermal ablation versus liver resection surgery in high surgical risk patients who would be eligible for liver resection. Pilot study objectives - to assess the feasibility of recruitment (through qualitative study), to assess the quality of ablations and liver resection surgery to determine acceptable standards for the main trial and to centrally review the reporting of computed tomography scan findings relating to ablation and outcomes and recurrence rate in both arms.A prospective, international (UK and the Netherlands), multicentre, open, pragmatic, parallel-group, randomised controlled non-inferiority trial with a 1-year internal pilot study.Tertiary liver, pancreatic and gallbladder (hepatopancreatobiliary) centres in the UK and the Netherlands.Adults with a specialist multidisciplinary team diagnosis of colorectal liver metastases who are at high surgical risk because of their age, comorbidities or tumour burden and who would be suitable for liver resection or thermal ablation.Thermal ablation conducted as per local policy (but centres were encouraged to recruit within Cardiovascular and Interventional Radiological Society of Europe guidelines) versus surgical liver resection performed as per centre protocol.Pilot study - patients' and clinicians' acceptability of the trial to assist in optimisation of recruitment. Primary outcome - disease-free survival at 2 years post randomisation. Secondary outcomes - overall survival, timing and site of recurrence, additional therapy after treatment failure, quality of life, complications, length of hospital stay, costs, trial acceptability, and disease-free survival measured from end of intervention. It was planned that 5-year survival data would be documented through record linkage. Randomisation was performed by minimisation incorporating a random element, and this was a non-blinded study.In the pilot study over 1 year, a total of 366 patients with colorectal liver metastases were screened and 59 were considered eligible. Only nine participants were randomised. The trial was stopped early and none of the planned statistical analyses was performed. The key issues inhibiting recruitment included fewer than anticipated patients eligible for both treatments, misconceptions about the eligibility criteria for the trial, surgeons' preference for one of the treatments ('lack of clinical equipoise' among some of the surgeons in the centre) with unconscious bias towards surgery, patients' preference for one of the treatments, and lack of dedicated research nurses for the trial.Recruitment feasibility was not demonstrated during the pilot stage of the trial; therefore, the trial closed early. In future, comparisons involving two very different treatments may benefit from an initial feasibility study or a longer period of internal pilot study to resolve these difficulties. Sufficient time should be allowed to set up arrangements through National Institute for Health Research (NIHR) Research Networks.Current Controlled Trials ISRCTN52040363.This project was funded by the NIHR Health Technology Assessment programme and will be published in full inIn about 50% of people with bowel cancer, cancer spreads to the liver (colorectal liver metastases) within 5 years of detection and treatment. Liver resection (i.e. surgical removal of a portion of the liver) is the standard treatment in people below 70 years of age who are otherwise well, provided that the liver cancer is confined to a limited part of the liver. Such patients are considered ‘low-risk’ patients. Older patients and those with major medical problems or extensive cancers are considered ‘high-risk’ patients, as they are at a higher risk of developing complications following liver resection. Thermal ablation destroys the liver cancers using a needle that heats the cancer deposits until they are destroyed. There is significant uncertainty as to whether or not ablation can offer equivalent survival compared with surgery for ‘high-risk’ patients. We planned and conducted a randomised controlled trial comparing ablation with surgery to resolve this uncertainty. In this trial, some patients received ablation and others received surgery. The treatment was allocated at random with neither patients nor the study organisers choosing the treatment. The trial had an internal pilot (i.e. a smaller version of the full trial to resolve any ‘teething problems’ and ensure that a sufficient number of participants can be included in the full trial). Only nine patients were recruited in the 1-year internal pilot, compared with the anticipated recruitment of 45 patients. Therefore, the trial closed early as a result of poor recruitment, and the uncertainty about the best treatment for high-risk patients with colorectal liver metastases continues. The main reasons for the poor recruitment included fewer than anticipated eligible participants, clinicians’ unconscious bias towards surgery, and patients’ preference for one treatment or the other. In the future, comparisons involving two very different treatments may benefit from a feasibility study or a longer period of pilot study to resolve any difficulties.

Aim Vagus nerve stimulation has emerged as a plausible intervention to reduce ileus after surgery. An early development study was undertaken with the aim of exploring the feasibility of self-administered, noninvasive vagus nerve stimulation (nVNS) after major colorectal surgery. Method A parallel-group, randomized controlled trial was undertaken between 1 January 2018 and 31 August 2019. Forty patients undergoing colorectal surgery for malignancy were allocated equally to Sham and Active stimulation groups. Electrical vagus nerve stimulation was self-administered bilaterally over the cervical surface landmarks for 5 days before and after surgery. Outcomes of interest were postoperative complications and adverse events measured using the Clavien-Dindo scale, treatment compliance, device usability according to the Systems Usability Scale (SUS) and clinical measures of bowel recovery. Results Forty patients were randomized and one withdrew, leaving 39 for analysis. Postoperative complications occurred in 9/19 (47.4%) participants receiving Sham and 11/20 (55.0%) receiving Active stimulation and were mostly minor. Compliance with treatment before surgery was 4.7 ± 0.9 days out of 5 days in the Sham group and 4.7 ± 1.1 in the Active group. Compliance with treatment after surgery was 4.1 ± 1.1 and 4.4 ± 1.5, respectively. Participants considered the intervention to be 'acceptable' according to the SUS. The most prominent differences in bowel recovery were days to first flatus (2.35 ± 1.32 vs 1.65 ± 0.88) and tolerance of solid diet (2.18 ± 2.21 vs 1.75 ± 0.91) for Sham and Active groups, respectively. Conclusion This study supports the safety, treatment compliance and usability of self-administered nVNS in patients undergoing major colorectal surgery.

You are the paediatric registrar at an epilepsy clinic. A mother of a 9-year-old patient with childhood absence epilepsy asks if he should be taking vitamin D. He is currently prescribed sodium valproate. You wonder if you should prescribe vitamin D supplementation alongside his antiepileptic medication. In children with a clinical diagnosis of epilepsy on antiepileptic drugs (AED) (population), is there evidence to suggest that they should receive supplemental vitamin D (intervention) to improve their bone health (outcome)? We searched OVID MEDLINE in June 2020 with the keywords (Child OR Paediatrics OR Pediatrics) AND (Vitamin D OR Vitamin D Deficiency OR Cholecalciferol OR Calcitriol) AND (Anti-Epileptic Drug OR Anti-Epileptic Medication OR Anti-Convulsant Drug). The search was limited to articles in English from the year 2000. Sixty-five articles were identified. Twenty articles were included after initial scrutiny and four were selected for full-text review. One further study was identified on review of article references. These were graded according to the Oxford level of evidence (table 1).1 View this table: Table 1 Summary of included studies Vitamin D deficiency is common worldwide. Vitamin D is protective for musculoskeletal health. Children treated with AED are known to have problems with bone metabolism and bone mineral density (BMD) loss. Enzyme-inducing AEDs (phenytoin, carbamazepine, primidone and phenytoin) increase vitamin D metabolism due to induction of cytochrome P450. Newer, non-enzyme-inducing antiepileptic drugs (NEIAEDs) can affect bone metabolism in a variety of ways, including stimulation of osteoclast activity, direct action on bone cells, parathyroid hormone resistance, inhibition of calcitonin secretion …

Background: Postoperative bowel dysfunction affects quality of life after sphincter-preserving rectal cancer surgery, but the extent of the problem is not clearly defined due to inconsistent outcome measures used to characterise the condition. Objective: The purpose of this study was to assess variation in reporting of postoperative bowel dysfunction and make recommendations for standardisation in future studies. If possible, a quantitative synthesis of bowel dysfunction symptoms was planned. Data Sources: MEDLINE and EMBASE databases and the Cochrane Library were queried between 2004-2015. Study Selection: The studies selected reported at least one component of bowel dysfunction following resection of rectal cancer. Main Outcome Measures: The main outcome measures were reporting, measurement and definition of post-operative bowel dysfunction. Results: Of 5428 studies identified, 234 met inclusion criteria. Widely reported components of bowel dysfunction were incontinence to stool (227/234; 97.0%), frequency (168/234; 71.8%) and incontinence to flatus (158/234; 67.5%). Urgency and stool clustering were reported less commonly, with rates of 106/234 (45.3%) and 61/234 (26.1%). Bowel dysfunction measured as a primary outcome was associated with better reporting (OR: 3.49; 95% CI: 1.99–6.23; P

Background A 17 year old with juvenile onset Huntington’s chorea was admitted to an adult hospice in Northern Ireland for symptom management and possible end of life care. The patient had been known to adult palliative care services in the?local hospital for approximately 10 months while under the care of the paediatric team and GP. The potential need for hospice admission for end of life care was recognised, but the nearest children’s hospice was far away and so admission to the local adult hospice was explored and facilitated. Aim To provide the adolescent patient and family with local hospice care. Methods A timebound, patient-named application for variation of age registration was successful with the Regulation and Quality Improvement Authority. The admission was planned collaboratively between paediatric and adult palliative care services. This joint-working continued following admission to the adult hospice. Outcome The initial move to the adult hospice presented challenges including recognition of dying in an adolescent; the patient’s limited communication and distressing symptoms; adjustment of family to a different care setting; staff anxieties with looking after a dying adolescent. Symptoms were more controlled and the patient died, with family there, almost two weeks following admission. Conclusion Flexibility by adult hospices regarding age restriction can help dying adolescents and their families to have access to inpatient hospice services when children’s hospices are far away. This may become more relevant as patient numbers increase (Together for Short Lives, 2015). Good communication and collaborative working by paediatric and adult palliative care services are crucial in overcoming the challenges, easing staff anxiety and in maintaining the young person at the centre.

AIM: Anastomotic leak (AL) is a major complication of rectal cancer surgery. Despite advances in surgical practice, the rates of AL have remained static, at around 10-15%. The aetiology of AL is multifactorial, but one of the most crucial risk factors, which is mostly under the control of the surgeon, is blood supply to the anastomosis. The MRC/NIHR IntAct study will determine whether assessment of anastomotic perfusion using a fluorescent dye (indocyanine green) and near-infrared laparoscopy can minimize the rate of AL leak compared with conventional white-light laparoscopy. Two mechanistic sub-studies will explore the role of the rectal microbiome in AL and the predictive value of CT angiography/perfusion studies. METHOD: IntAct is a prospective, unblinded, parallel-group, multicentre, European, randomized controlled trial comparing surgery with intra-operative fluorescence angiography (IFA) against standard care (surgery with no IFA). The primary end-point is rate of clinical AL at 90 days following surgery. Secondary end-points include all AL (clinical and radiological), change in planned anastomosis, complications and re-interventions, use of stoma, cost-effectiveness of the intervention and quality of life. Patients should have a diagnosis of adenocarcinoma of the rectum suitable for potentially curative surgery by anterior resection. Over 3 years, 880 patients from 25 European centres will be recruited and followed up for 90 days. DISCUSSION: IntAct will rigorously evaluate the use of IFA in rectal cancer surgery and explore the role of the microbiome in AL and the predictive value of preoperative CT angiography/perfusion scanning.

BackgroundProtein biomarkers with associations with the activity and outcomes of diseases are being identified by modern proteomic technologies. They may be simple, accessible, cheap and safe tests that can inform diagnosis, prognosis, treatment selection, monitoring of disease activity and therapy and may substitute for complex, invasive and expensive tests. However, their potential is not yet being realised.Design and methodsThe study consisted of three workstreams to create a framework for research: workstream 1, methodology – to define current practice and explore methodology innovations for biomarkers for monitoring disease; workstream 2, clinical translation – to create a framework of research practice, high-quality samples and related clinical data to evaluate the validity and clinical utility of protein biomarkers; and workstream 3, the ELF to Uncover Cirrhosis as an Indication for Diagnosis and Action for Treatable Event (ELUCIDATE) randomised controlled trial (RCT) – an exemplar RCT of an established test, the ADVIA Centaur® Enhanced Liver Fibrosis (ELF) test (Siemens Healthcare Diagnostics Ltd, Camberley, UK) [consisting of a panel of three markers – (1) serum hyaluronic acid, (2) amino-terminal propeptide of type III procollagen and (3) tissue inhibitor of metalloproteinase 1], for liver cirrhosis to determine its impact on diagnostic timing and the management of cirrhosis and the process of care and improving outcomes.ResultsThe methodology workstream evaluated the quality of recommendations for using prostate-specific antigen to monitor patients, systematically reviewed RCTs of monitoring strategies and reviewed the monitoring biomarker literature and how monitoring can have an impact on outcomes. Simulation studies were conducted to evaluate monitoring and improve the merits of health care. The monitoring biomarker literature is modest and robust conclusions are infrequent. We recommend improvements in research practice. Patients strongly endorsed the need for robust and conclusive research in this area. The clinical translation workstream focused on analytical and clinical validity. Cohorts were established for renal cell carcinoma (RCC) and renal transplantation (RT), with samples and patient data from multiple centres, as a rapid-access resource to evaluate the validity of biomarkers. Candidate biomarkers for RCC and RT were identified from the literature and their quality was evaluated and selected biomarkers were prioritised. The duration of follow-up was a limitation but biomarkers were identified that may be taken forward for clinical utility. In the third workstream, the ELUCIDATE trial registered 1303 patients and randomised 878 patients out of a target of 1000. The trial started late and recruited slowly initially but ultimately recruited with good statistical power to answer the key questions. ELF monitoring altered the patient process of care and may show benefits from the early introduction of interventions with further follow-up. The ELUCIDATE trial was an ‘exemplar’ trial that has demonstrated the challenges of evaluating biomarker strategies in ‘end-to-end’ RCTs and will inform future study designs.ConclusionsThe limitations in the programme were principally that, during the collection and curation of the cohorts of patients with RCC and RT, the pace of discovery of new biomarkers in commercial and non-commercial research was slower than anticipated and so conclusive evaluations using the cohorts are few; however, access to the cohorts will be sustained for future new biomarkers. The ELUCIDATE trial was slow to start and recruit to, with a late surge of recruitment, and so final conclusions about the impact of the ELF test on long-term outcomes await further follow-up. The findings from the three workstreams were used to synthesise a strategy and framework for future biomarker evaluations incorporating innovations in study design, health economics and health informatics.Trial registrationCurrent Controlled Trials ISRCTN74815110, UKCRN ID 9954 and UKCRN ID 11930.FundingThis project was funded by the NIHR Programme Grants for Applied Research programme and will be published in full inProgramme Grants for Applied Research; Vol. 6, No. 3. See the NIHR Journals Library website for further project information.

Background Although surgical resection has been considered the only curative option for colorectal liver metastases (CLM), thermal ablation has recently been suggested as an alternative curative treatment. A prospective randomised trial is required to define the efficacy of resection vs ablation for the treatment of colorectal liver metastases. Methods Design and setting: This is a multicentre, open, randomised controlled non-inferiority trial design with internal pilot and will be performed in tertiary liver centres in UK and The Netherlands. Participants: Eligible patients will be those with colorectal liver metastases at high surgical risk because of their age, co-morbidities or tumour burden and who would be suitable for liver resection or thermal ablation. Intervention: Thermal ablation as per local policy. Control: Surgical liver resection performed as per centre protocol. Co-interventions: Further chemotherapy will be offered to patients as per current practice. Outcomes Pilot study: Same as main study and in addition patients and clinicians’ acceptability of the trial to assist in optimisation of recruitment. Primary outcome: Disease-free survival (DFS) at two years post randomisation. Secondary outcomes: Overall survival, timing and site of recurrence, additional therapy after treatment failure, quality of life, complications, length of hospital stay, costs, trial acceptability, DFS measured from end of intervention. Follow-up: 24 months from randomisation; five-year follow-up for overall survival. Sample size: 330 patients to demonstrate non-inferiority of thermal ablation. Discussion This trial will determine the effectiveness and cost-effectiveness of thermal ablation vs surgical resection for high-risk people with colorectal liver metastases, and guide the optimal treatment for these patients. Trial registration ISRCTN Registry, ISRCTN52040363. Registered on 9 March 2016. Electronic supplementary material The online version of this article (10.1186/s13063-018-2499-5) contains supplementary material, which is available to authorized users.

Background5-aminolevulinic acid (5-ALA) is used for fluorescence diagnosis (FD) in neurological, gynaecological and urological malignancies. The Medical Research Council/Efficacy and Mechanism Evaluation (EME) programme/National Institute for Health Research’s Next Generation intraoperative Lymph node staging for Stratified colon cancer surgery (GLiSten) study investigated its use to predict lymph node (LN)-positive disease in colon cancer as an aid to stratified surgery.ObjectivesThe primary objective was to optimise the dose of oral 5-ALA for intraoperative FD of metastatic LNs in colon cancer. Secondary objectives included standardisation of pre-operative computerised tomography (CT) LN reporting, intraoperative fluorescence detection, surgical resection with D3 lymphadenectomy and histopathological examination of resected specimens.DesignThis was a feasibility study to determine optimal strategies for 5-ALA positive LN detection. Patients with locally advanced disease identified using the Fluoropyrimidine, Oxaliplatin and Targeted-Receptor pre-Operative Therapy for patients with high-risk, operable colon cancer (FOxTROT) criteria were recruited from two sites between October 2013 and June 2015. Cohort 1 received 20 mg/kg and cohort 2 received 30 mg/kg of oral 5-ALA, 1–6 hours preoperatively. Laparoscopic assessment of fluorescence was performed using the Storz D-Light system (KARL STORZ GmbH & Co. KG; Tuttlingen, Germany), with marking of fluorescent LNs, followed by oncological resection. The specimen was subjected to histological analysis with step sectioning of marked fluorescent LNs. Progression to an evaluation phase using the optimal dosing schedule was dependent on positively identifying at least 2 out of 10 patients with metastatic LN disease in either cohort.ResultsA total of 44 patients were recruited with a male to female ratio of 26 : 18 and a mean age of 71 years (range 52–88 years). Cohort 1 consisted of 18 patients, of whom six had fluorescent primary cancers and three of these had fluorescent LNs. One out of 10 patients with metastatic LN disease had a fluorescent involved LN. Cohort 2 consisted of 26 patients, of whom eight had fluorescent primary cancers and four of these had fluorescent LNs. None of the fluorescent LNs contained disease in this cohort. No serious adverse events (SAEs) occurred but two mild, self-limiting, photosensitivity reactions were observed in cohort 2. The sensitivity and specificity for 5-ALA detection of LN-positive disease were: cohort 1 11.1%, 75%; and cohort 2 0%, 75%.LimitationsThis was a feasibility study exploring the use of 5-ALA for LN disease in a select cohort of patients with advanced colorectal cancer. The study population was small and generalisation to other cancers is not possible. The study was limited by the ability to determine LN-positive patients on the basis of pre-operative CT staging, which is often inaccurate, resulting in our cohorts containing several patients without LN disease.Conclusions5-ALA fluorescent diagnosis has poor sensitivity for discriminating LN-positive colon cancer. Its use as an aid to stratified colon cancer surgery is not supported. No SAEs were observed, suggesting that photosensitisers may be useful for intraoperative FD.Future work5-ALA has poor sensitivity for detecting LN metastases and cannot be recommended for intraoperative staging. Other, more sensitive fluorescent probes are required if this strategy is to be used.Study registrationCurrent Controlled Trials ISRCTN79949827 and EudraCT number 2012–002623–15.Funding detailsThis project was funded by the EME programme, a Medical Research Council and National Institute for Health Research partnership.

PURPOSE: Faecal incontinence is a physically, psychologically and socially disabling condition. NICE guidance (2007) recommends surgical intervention, including sacral nerve stimulation (SNS), after failed conservative therapies. The FENIX magnetic sphincter augmentation (MSA) device is a novel continence device consisting of a flexible band of interlinked titanium beads with magnetic cores that is placed around the anal canal to augment anal sphincter tone through passive attraction of the beads. Preliminary studies suggest the FENIX MSA is safe, but efficacy data is limited. Rigorous evaluation is required prior to widespread adoption. METHOD AND DESIGN: The SaFaRI trial is a National Institute of Health Research (NIHR) Health Technology Assessment (HTA)-funded UK multi-site, parallel group, randomised controlled, unblinded trial that will investigate the use of the FENIX MSA, as compared to SNS, for adult faecal incontinence resistant to conservative management. Twenty sites across the UK, experienced in the treatment of faecal incontinence, will recruit 350 patients randomised equally to receive either SNS or FENIX MSA. Participants will be followed-up at 2 weeks post-surgery and at 6, 12 and 18 months post-randomisation. The primary endpoint is success, as defined by device in use and ≥50 % improvement in the Cleveland Clinic Incontinence Score (CCIS) at 18 months post-randomisation. Secondary endpoints include complications, quality of life and cost effectiveness. DISCUSSION: SaFaRI will rigorously evaluate a new technology for faecal incontinence, the FENIX™ MSA, allowing its safe and controlled introduction into current clinical practice. These results will inform the future surgical management of adult faecal incontinence.

Objective In 2001, the National Institute for Health Research Cancer Research Network (NCRN) was established, leading to a rapid increase in clinical research activity across the English NHS. Using colorectal cancer (CRC) as an example, we test the hypothesis that high, sustained hospital-level participation in interventional clinical trials improves outcomes for all patients with CRC managed in those research-intensive hospitals. Design Data for patients diagnosed with CRC in England in 2001–2008 (n=209 968) were linked with data on accrual to NCRN CRC studies (n=30 998). Hospital Trusts were categorised by the proportion of patients accrued to interventional studies annually. Multivariable models investigated the relationship between 30-day postoperative mortality and 5-year survival and the level and duration of study participation. Results Most of the Trusts achieving high participation were district general hospitals and the effects were not limited to cancer ‘centres of excellence’, although such centres do make substantial contributions. Patients treated in Trusts with high research participation (≥16%) in their year of diagnosis had lower postoperative mortality (p

Importance Robotic rectal cancer surgery is gaining popularity, but limited data are available regarding safety and efficacy. Objective To compare robotic-assisted vs conventional laparoscopic surgery for risk of conversion to open laparotomy among patients undergoing resection for rectal cancer. Design, Setting, and Participants Randomized clinical trial comparing robotic-assisted vs conventional laparoscopic surgery among 471 patients with rectal adenocarcinoma suitable for curative resection conducted at 29 sites across 10 countries, including 40 surgeons. Recruitment of patients was from January 7, 2011, to September 30, 2014, follow-up was conducted at 30 days and 6 months, and final follow-up was on June 16, 2015. Interventions Patients were randomized to robotic-assisted (n = 237) or conventional (n = 234) laparoscopic rectal cancer resection, performed by either high (upper rectum) or low (total rectum) anterior resection or abdominoperineal resection (rectum and perineum). Main Outcomes and Measures The primary outcome was conversion to open laparotomy. Secondary end points included intraoperative and postoperative complications, circumferential resection margin positivity (CRM+) and other pathological outcomes, quality of life (36-Item Short Form Survey and 20-item Multidimensional Fatigue Inventory), bladder and sexual dysfunction (International Prostate Symptom Score, International Index of Erectile Function, and Female Sexual Function Index), and oncological outcomes. Results Among 471 randomized patients (mean [SD] age, 64.9 [11.0] years; 320 [67.9%] men), 466 (98.9%) completed the study. The overall rate of conversion to open laparotomy was 10.1%: 19 of 236 patients (8.1%) in the robotic-assisted laparoscopic group and 28 of 230 patients (12.2%) in the conventional laparoscopic group (unadjusted risk difference = 4.1% [95% CI, −1.4% to 9.6%]; adjusted odds ratio = 0.61 [95% CI, 0.31 to 1.21];P = .16). The overall CRM+ rate was 5.7%; CRM+ occurred in 14 (6.3%) of 224 patients in the conventional laparoscopic group and 12 (5.1%) of 235 patients in the robotic-assisted laparoscopic group (unadjusted risk difference = 1.1% [95% CI, −3.1% to 5.4%]; adjusted odds ratio = 0.78 [95% CI, 0.35 to 1.76];P = .56). Of the other 8 reported prespecified secondary end points, including intraoperative complications, postoperative complications, plane of surgery, 30-day mortality, bladder dysfunction, and sexual dysfunction, none showed a statistically significant difference between groups. Conclusions and Relevance Among patients with rectal adenocarcinoma suitable for curative resection, robotic-assisted laparoscopic surgery, as compared with conventional laparoscopic surgery, did not significantly reduce the risk of conversion to open laparotomy. These findings suggest that robotic-assisted laparoscopic surgery, when performed by surgeons with varying experience with robotic surgery, does not confer an advantage in rectal cancer resection. Trial Registration isrctn.org Identifier:ISRCTN80500123

Background There are many methodological challenges in the conduct and analysis of cluster randomised controlled trials, but one that has received little attention is that of post-randomisation changes to cluster composition. To illustrate this, we focus on the issue of cluster merging, considering the impact on the design, analysis and interpretation of trial outcomes. Methods We explored the effects of merging clusters on study power using standard methods of power calculation. We assessed the potential impacts on study findings of both homogeneous cluster merges (involving clusters randomised to the same arm of a trial) and heterogeneous merges (involving clusters randomised to different arms of a trial) by simulation. To determine the impact on bias and precision of treatment effect estimates, we applied standard methods of analysis to different populations under analysis. Results Cluster merging produced a systematic reduction in study power. This effect depended on the number of merges and was most pronounced when variability in cluster size was at its greatest. Simulations demonstrate that the impact on analysis was minimal when cluster merges were homogeneous, with impact on study power being balanced by a change in observed intracluster correlation coefficient (ICC). We found a decrease in study power when cluster merges were heterogeneous, and the estimate of treatment effect was attenuated. Conclusions Examples of cluster merges found in previously published reports of cluster randomised trials were typically homogeneous rather than heterogeneous. Simulations demonstrated that trial findings in such cases would be unbiased. However, simulations also showed that any heterogeneous cluster merges would introduce bias that would be hard to quantify, as well as having negative impacts on the precision of estimates obtained. Further methodological development is warranted to better determine how to analyse such trials appropriately. Interim recommendations include avoidance of cluster merges where possible, discontinuation of clusters following heterogeneous merges, allowance for potential loss of clusters and additional variability in cluster size in the original sample size calculation, and use of appropriate ICC estimates that reflect cluster size.