Establishing the learning curve of transanal minimally invasive surgery for local excision of rectal neoplasms

Introduction Transanal minimally invasive surgery (TAMIS) is an endoscopic operating platform for local excision of rectal neoplasms. However, it may be technically demanding, and its learning curve has yet to be adequately defined. The objective of this study was to determine the number of TAMIS procedures for the local excision of rectal neoplasm required to reach proficiency. Methods and procedures All TAMIS cases performed from 07/2009 to 12/2016 at a single high-volume tertiary care institution for local excision of benign and malignant rectal neoplasia were identified from a prospective database. A cumulative summation (CUSUM) analysis was performed to determine the number of cases required to reach proficiency. The main proficiency outcome was rate of margin positivity (R1 resection). The acceptable and unacceptable R1 rates were defined as the R1 rate of transanal endoscopic microsurgery (TEM-10%) and traditional transanal excision (TAE-26%), which was obtained from previously published meta-analyses. Comparisons of patient, tumor, and operative characteristics before and after TAMIS proficiency were performed. Results A total of 254 TAMIS procedures were included in this study. The overall R1 resection rate was 7%. The indication for TAMIS was malignancy in 57%. CUSUM analysis reported that TAMIS reached an acceptable R1 rate between 14 and 24 cases. Moving average plots also showed that the mean operative times stabilized by proficiency gain. The mean lesion size was larger after proficiency gain (3.0 cm (SD 1.5) vs. 2.3 cm (SD 1.3), p = 0.008). All other patient, tumor, and operative characteristics were similar before and after proficiency gain. Conclusions TAMIS for local excision of rectal neoplasms is a complex procedure that requires a minimum of 14-24 cases to reach an acceptable R1 resection rate and lower operative duration.