Background: Transanal total mesorectal excision (TaTME) for rectal cancer has emerged as an alternative to the traditional abdominal approach. However, concerns have been raised about local recurrence. The aim of this study was to evaluate local recurrence after TaTME. Secondary aims included postoperative mortality, anastomotic leak and stoma rates. Methods: Data on all patients who underwent TaTME were recorded and compared with those from national cohorts in the Norwegian Colorectal Cancer Registry (NCCR) and the Norwegian Registry for Gastrointestinal Surgery (NoRGast). Kaplan-Meier estimates were used to compare local recurrence. Results: In Norway, 157 patients underwent TaTME for rectal cancer between October 2014 and October 2018. Three of seven hospitals abandoned TaTME after a total of five procedures. The local recurrence rate was 12 of 157 (7⋅6 per cent); eight local recurrences were multifocal or extensive. The estimated local recurrence rate at 2⋅4 years was 11⋅6 (95 per cent c.i. 6⋅6 to 19⋅9) per cent after TaTME compared with 2⋅4 (1⋅4 to 4⋅3) per cent in the NCCR (P < 0⋅001). The adjusted hazard ratio was 6⋅71 (95 per cent c.i. 2⋅94 to 15⋅32). Anastomotic leaks resulting in reoperation occurred in 8⋅4 per cent of patients in the TaTME cohort compared with 4⋅5 per cent in NoRGast (P = 0⋅047). Fifty-six patients (35⋅7 per cent) had a stoma at latest follow-up; 39 (24⋅8 per cent) were permanent.Conclusion: Anastomotic leak rates after TaTME were higher than national rates; local recurrence rates and growth patterns were unfavourable.

Emergency operation for colon cancer was associated with high rates of complications and mortality, indicating that immediate surgery should be avoided if possible. Decompression of left sided obstruction with a stent seems promising, whereas no conclusion can be made with regard to optimal procedure if stent placement fails; in this study Hartmann's procedure was associated with high mortality and morbidity.

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The incidence of colorectal cancer (CRC) increases with age and early onset indicates an increased likelihood for genetic predisposition for this disease. The somatic genetics of tumor development in relation to patient age remains mostly unknown. We have examined the mutation status of five known cancer critical genes in relation to age at diagnosis, and compared the genomic complexity of tumors from young patients without known CRC syndromes with those from elderly patients. Among 181 CRC patients, stratified by microsatellite instability status, DNA sequence changes were identified in KRAS (32%), BRAF (16%), PIK3CA (4%), PTEN (14%) and TP53 (51%). In patients younger than 50 years (n = 45), PIK3CA mutations were not observed and TP53 mutations were more frequent than in the older age groups. The total gene mutation index was lowest in tumors from the youngest patients. In contrast, the genome complexity, assessed as copy number aberrations, was highest in tumors from the youngest patients. A comparable number of tumors from young (<50 years) and old patients (>70 years) was quadruple negative for the four predictive gene markers (KRAS-BRAF-PIK3CA-PTEN); however, 16% of young versus only 1% of the old patients had tumor mutations in PTEN/PIK3CA exclusively. This implies that mutation testing for prediction of EGFR treatment response may be restricted to KRAS and BRAF in elderly (>70 years) patients. Distinct genetic differences found in tumors from young and elderly patients, whom are comparable for known clinical and pathological variables, indicate that young patients have a different genetic risk profile for CRC development than older patients.