Assessment of safety and efficacy of Transanal Total Mesorectal Excision [TaTME] by Observational Clinical Human Reliability Analysis [OCHRA] and analysis of international registry data

Abstract

The introduction of any new surgical technique should undergo a vigorous process of development and implementation, that ensures a safe and controlled clinical adoption. Transanal Total Mesorectal Excision (TaTME) for rectal cancer attracted great interest and enthusiasm amongst the colorectal community following its first live case in 2009; postulating numerous advantages over conventional abdominal rectal cancer surgery. The aim of this PhD thesis was to evaluate the safety and efficacy of TaTME by analyzing outcomes recorded on the international TaTME registry and assessing the actual technique itself in detail by performing Observational Clinical Human Reliability Analysis (OCHRA).

Three main aspects were explored through data recorded on the TaTME registry by surgeons worldwide: 1) Histopathological outcomes during the initial stage of TaTME experience, 2) Clinical outcomes following TaTME with particular focus on anastomotic failure rates; 3) Proficiency-gain curve of TaTME. Overall outcomes have been very encouraging with a low R1 resection rate of 2.7% and acceptable overall 30-day morbidity of 32.6%. The early anastomotic leak rate from a cohort of 1594 was 7.8% and overall anastomotic-related problems (anastomotic failure) was 15.7%. The occurrence of an unexpected intra-operative complication, namely urethral injury, was also highlighted with an incidence of 0.8%. Proficiency-gain curve analysis using the risk adjusted cumulative sum (CUSUM) method applied to 2751 TaTME cases from 154 surgical units, revealed that intra-operative adverse events showed a change point with improvement in performance after the initial 10 restorative procedures. Histological outcomes and overall post-operative 30-day complications did not produce a meaningful learning curve, whereas anastomotic failure had a clearer picture with a peak or change point reached after the initial 15 cases, followed by a “slow transition” period between cases 15 and 49, after which improvements were seen more clearly.

Systematic analysis of the technique by OCHRA provided a greater understanding of what types of errors occur and the ‘error-pathways’ that lead to an adverse intra-operative event, as well as what constitutes an optimal technical performance. A clinical categorisation of technical errors was devised including errors of set up/exposure, and executional errors divided into tissue-instrument interface errors and instrument-handling errors. Overall 5101 errors and 904 adverse consequences were logged in 100 transanal operations, with a mean of 51 ±32.4 errors and 9 ±6.6 adverse consequences per case. A technical accuracy scoring system was developed for the transanal operation with higher scores indicating a poorer technical performance with more errors committed. An accuracy score above 24 was found to significantly increase the risk of post-operative complications (15.8% vs 42.9%, Odds ratio 4.00, 95% CI 1.415–11.310, p 0.007). Semi-structured interviews and face-to-face workshop with international TaTME experts lead to the development of error-reducing mechanisms and technical recommendations to help guide future training and as a useful resource for all TaTME surgeons. An OCHRA feedback form incorporating the learning points and recommendations has been developed during the national TaTME training programme in the UK.

In conclusion, TaTME is a technically demanding operation which has the potential to allow optimal oncological resections especially in more challenging cases. However, thorough structured training in the technique is essential and its true benefits over conventional approaches remain to be determined.