GASTROINTESTINAL STROMAL TUMOR OF THE RECTUM TREATED WITH NEOADJUVANT IMATINIB FOLLOWED BY TRANSANAL ENDOSCOPIC MICROSURGERYArq Bras Cir Dig. 2015;28(1):87-9. doi: 10.1590/S0102-67202015000100022.

Gastrointestinal stromal tumor of the rectum treated with neoadjuvant Imatinib followed by transanal endoscopic microsurgery.

[Article in English, Portuguese]

Nahas CS1, Nahas SC1, Marques CF1, Schmerling R1, Bustamante-Lopez LA1, Ribeiro U1, Cecconello I1.

From the Department of Gastroenterology, Surgical Division, Clinic Hospital,
School of Medicine, University of São Paulo, São Paulo, Brazil.

Introduction: The gastrointestinal stromal tumor (GIST) is a rare type of tumor that expresses CD117 oncogene that can be detected by immunohistochemistry. The most common sites of GISTs are stomach (70%), and small intestine (20%), while rectum is comprised in only 3% of the cases. Although a rare condition, the GIST located in the distal rectum may require an abdominoperineal resection. There is no data to support the use of Imatinib (Gleevec from Novartis, Basel, Switzerland), a selective inhibitor of tyrosine quinase, as neoadjuvant therapy. However, the last session consensus for the treatment of GIST, suggests that this form of therapy can be used in some cases where anal sphincter is involved.

Objective: is to describe a case of distal rectum GIST in the rectovaginal septum with partial invasion of the anal sphincter, which was successfully treated by neoadjuvant therapy with imatinib followed by the technique of transanal endoscopic microsurgery (TEM).

Methods: TEM suturing technique could not be used in this case since it was not possible to keep the gas insufflation at the anal verge (the TEM retoscope could not seal the anus). The vaginal wall was also closed primarily with a transvaginal running suture. A laparoscopic loop ileostomy was created to prevent from rectovaginal fistulae.

Results: The postoperative period was uneventful and the patient was sent home on 4th day. The loop ileostomy was taken down four months later and the patient recovered normal defecation with minimal transient fecal incontinence. Pathological analysis of the surgical specimen identified a white firm 3.5x3.0x3.0 cm well delimited rectal mass, occupying the adjacent soft tissue close to the vagina interface. The specimen margins were free of tumor. The lesion expressed CD34 or CD117 and showed no mitotic activity (zero mitoses in 50 HPF). As for now, the patient presented no evidence of recurrence of disease (follow up period of 46.2 months).

Conclusion: The use of neoadjuvant Imatinib should be considered in patients with GIST of distal rectum in order to possibilitate sphincter preservation.