17Study question 18 Can mitochondrial DNA (mtDNA) levels in trophectodermal cells of the blastocyst predict the 19 blastocyst quality, ploidy status, implantation rate and clinical outcomes? 20 Summary answer 21 mtDNA levels in trophectodermal cells of the blastocyst do not associate with the blastocyst 22 quality, ploidy status, implantation potential and clinical outcomes, but can differentiate between 23 aneuploid and euploid blastocysts.24 What we already know 25 mtDNA levels in the trophectodermal cells have been suggested to be associated with blastocyst 26 morphology, ploidy and implantation rates, and has been proposed as biomarker to access 27 blastocyst quality and predict clinical outcomes. However, discrepancies exist if mtDNA levels 28 could serve as a marker for the same.29 Study design and duration 30

Introduction Transanal total mesorectal excision (TaTME) has rapidly emerged as a novel approach for rectal cancer surgery. Safety profiles are still emerging and more comparative data is urgently needed. This study aimed to compare indications and short‐term outcomes of TaTME, open, laparoscopic, and robotic TME internationally. Methods A pre‐planned analysis of the European Society of Coloproctology (ESCP) 2017 audit was performed. Patients undergoing elective total mesorectal excision (TME) for malignancy between 1 January 2017 and 15 March 2017 by any operative approach were included. The primary outcome measure was anastomotic leak. Results Of 2579 included patients, 76.2% (1966/2579) underwent TME with restorative anastomosis of which 19.9% (312/1966) had a minimally invasive approach (laparoscopic or robotic) which included a transanal component (TaTME). Overall, 9.0% (175/1951, 15 missing outcome data) of patients suffered an anastomotic leak. On univariate analysis both laparoscopic TaTME (OR 1.61, 1.02–2.48, P = 0.04) and robotic TaTME (OR 3.05, 1.10–7.34, P = 0.02) were associated with a higher risk of anastomotic leak than non‐transanal laparoscopic TME. However this association was lost in the mixed‐effects model controlling for patient and disease factors (OR 1.23, 0.77–1.97, P = 0.39 and OR 2.11, 0.79–5.62, P = 0.14 respectively), whilst low rectal anastomosis (OR 2.72, 1.55–4.77, P < 0.001) and male gender (OR 2.29, 1.52–3.44, P < 0.001) remained strongly associated. The overall positive circumferential margin resection rate was 4.0%, which varied between operative approaches: laparoscopic 3.2%, transanal 3.8%, open 4.7%, robotic 1%. Conclusion This contemporaneous international snapshot shows that uptake of the TaTME approach is widespread and is associated with surgically and pathologically acceptable results.

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Introduction The mainstay of management for locally advanced rectal cancer is chemoradiotherapy followed by surgical resection. Following chemoradiotherapy, a complete response may be detected clinically and radiologically (cCR) prior to surgery or pathologically after surgery (pCR). We aim to report the overall complete pathological response (pCR) rate and the reliability of detecting a cCR by conventional pre‐operative imaging. Methods A pre‐planned analysis of the European Society of Coloproctology (ESCP) 2017 audit was performed. Patients treated by elective rectal resection were included. A pCR was defined as a ypT0 N0 EMVI negative primary tumour; a partial response represented any regression from baseline staging following chemoradiotherapy. The primary endpoint was the pCR rate. The secondary endpoint was agreement between post‐treatment MRI restaging (yMRI) and final pathological staging. Results Of 2572 patients undergoing rectal cancer surgery in 277 participating centres across 44 countries, 673 (26.2%) underwent chemoradiotherapy and surgery. The pCR rate was 10.3% (67/649), with a partial response in 35.9% (233/649) patients. Comparison of AJCC stage determined by post‐treatment yMRI with final pathology showed understaging in 13% (55/429) and overstaging in 34% (148/429). Agreement between yMRI and final pathology for T‐stage, N‐stage, or AJCC status were each graded as ‘fair’ only (n = 429, Kappa 0.25, 0.26 and 0.35 respectively). Conclusion The reported pCR rate of 10% highlights the potential for non‐operative management in selected cases. The limited strength of agreement between basic conventional post‐chemoradiotherapy imaging assessment techniques and pathology suggest alternative markers of response should be considered, in the context of controlled clinical trials.