Transanal minimally invasive surgery (TAMIS) for anterior rectal GIST

Abstract

The incidence of gut gastrointestinal stromal tumors (GISTs) is less than 1%, 90% found in the stomach or small intestine, and only 3% are located in the rectum. Treatment of rectal GISTs needs careful planning in order to preserve the rectum and sphincters where possible. Neoadjuvant therapy has extended the indications for local excisions [1]. Several approaches for local, sphincter-preserving resection of GISTs have been described. The transanal (Parks) and transsacral (Kraske) techniques can achieve a complete resection in lowand mid-rectal lesions with low morbidity and mortality but usually require fragmentation of the specimen with an increased risk of local recurrence [2]. Anteriorly located GISTs are particularly challenging. Transvaginal excision has been described for high anterior rectal wall lesions, with the advantage of avoiding anal dysfunction [3]. Another method is the perineal approach, which has been implemented for GISTs on the anterior rectal wall [4]. More recently, transanal minimally invasive endoscopic excision has been described. This includes transanal minimally invasive surgery (TAMIS), transanal endoscopic microsurgery (TEM) and transanal endoscopic operation (TEO) [5]. Advantages of these techniques are that clear resection margins and intact specimens produced may lead to improved outcomes. The attached video shows a TAMIS procedure performed on a 60-year-old male diagnosed with prostatic adenocarcinoma and a 2.5 cm rectal GIST located on the anterior rectal wall, 2 cm from the anus, not clearly separated from the prostate on magnetic resonance imaging (MRI). Positron emission tomography (PET) scan was negative. Restaging MRI after 6 months of imatinib therapy showed a good radiological response: the lesion was downsized to 1.5 cm. On October 2016, the patient had robotic prostatectomy with bilateral obturator lymphadenectomy. Three months later, imatinib was restarted and in June 2017 he was referred to our colorectal center. At restaging MRI, the nodule had increased in size (2.5 cm) and slightly compressed the posterior urethra. PET scan was negative. Due to the lack of response to continued imatinib treatment, the multidisciplinary board advised surgery. The lesion was approached transanally using the TAMIS platform. The operation began with the positioning of a Lone Star retractor, identification of the nodule with palpation and demarcation of its borders with electrocautery. After that, the GelPoint Path (Applied Medical, Inc., Rancho Santa Margarita, CA, USA) was inserted and pneumorectum was started. The circumferential demarcation of the nodule was completed and a 360° dissection down to the muscular layer was performed. The resection proceeded along an avascular plane with care taken to keep the tumor capsule intact and avoid injuring the posterior urethra. After complete removal of the tumor, the defect was closed with a barbed suture. Histology confirmed a 2.7 cm GIST, CD34 + , DOG1 + , with a deletion in exon 11 of c-kit at mutational analysis. The patient was discharged on postoperative day 2. Imatinib was restarted 3 weeks after the operation. At 8 month follow-up, the patient was in good clinical condition and MRI showed that he was disease free. Key points of this case are related to the site (GIST of the anterior rectal wall, adherent to the posterior urethra), Electronic supplementary material The online version of this article (https ://doi.org/10.1007/s1015 1-019-01979 -y) contains supplementary material, which is available to authorized users.