Transanal endoscopic microsurgery with alternative neoadjuvant imatinib for localized rectal gastrointestinal stromal tumor: a single center experience with long-term surveillance.

[BACKGROUND] Transanal endoscopic microsurgery (TEM) is widely used in the treatment of local rectal lesions and helps avoid radical surgery. This study evaluated the management and outcome in a long-term followed cohort of patients with localized rectal GIST underwent TEM with alternative neodajuvant imatinib (nIM).

[METHODS] A retrospective cohort study was undertaken of patients identified from a case database at Department of General Surgery, Peking Union Medical College Hospital (PUMCH) over a continuous period, from January 2006 to December 2017.

[RESULTS] Over 12 years, 42 patients presented with a primary rectal GIST in PUMCH. Median age was 49 (range 27-77) years. Neoadjuvant imatinib (nIM) therapy was used in 16 patients, significantly reducing mean tumor size from 4.41 to 2.46 cm (p < 0.001) and mitotic index (p = 0.041). All of these patients underwent TEM with no tumor rupture, nIM therapy enabled sphincter-preserving surgery to be undertaken in 16 (16/42) patients who would otherwise have required abdominoperineal resection or pelvic exenteration for tumor clearance and all patients (42/42) achieve R0 resection and negative margin. Imatinib was also used as postoperative adjuvant treatment in 15 patients with high-risk GIST. Median follow-up was 77 (range 14-144) and overall survival is 100%. In 42 patients, Local recurrence (LR) occurred in 3 of 42 patients and 1 of 42 patients developed distant metastasis (DM) in 112 months after TEM. In the univariate analysis, mitotic index (p = 0.028), NIH risk categories (p = 0.047) were predictive feature of local relapse.

[CONCLUSION] The application of nIM significantly decreased tumor size in large localized rectal GIST, which permitted TEM to preserve sphincter. The TEM procedure with alternative neoadjuvant imatinib therapy is a practicable treatment for patients with rectal GIST to preserve anus and have satisfied anal function.