LAUSR

Editor Seow-En and Seow-Choen highlight the learning curve phenomenon in surgery, and suggest that this explains the high rate of local recurrence (LR) in the Norwegian study1. The study cannot confirm whether the main contributor to the negative results was inferiority in performance due to the learning curve phenomenon or potential pitfalls in the method. Only external scientific validation can do this. It is not possible to conclude from positive results in unadjusted observational studies that any negative results are due to unskilled performance. The method should be investigated in a proper RCT that avoids at least two main pitfalls; the ‘poor’ arm problem and inclusion of only low-risk tumours. In ordinary total mesorectal excision (TME), a very high proportion of patients are not at clear risk for LR. The Norwegian study adjusts for case mix and some selection biases; this is lacking in many observational studies. In Norway, chemoradiotherapy (CRT) is given irrespective of surgical method. CRT is an essential disturbing confounder, particularly as it cures many patients before surgery. When adjusted for CRT, this factor did not affect the high hazard ratio for LR after transanal total mesorectal excision (TaTME). Norwegian guidelines stress that any surgeon who carries out TaTME must be properly trained. We assumed the surgeons were confident with the method. All were experienced surgeons who had excellent documented results in traditional TME surgery. Experienced surgeons at three institutions found the method too challenging for curing malignant disease. All four TaTME hospitals had LRs. When negative results occur, it is too easy to blame the learning curve in order to save the method, but long learning curves are no longer acceptable in oncological surgery.