Transanal minimally invasive surgery (TAMIS) approach for large juxta-anal gastrointestinal stromal tumour.

Gastrointestinal stromal tumours (GISTs) are rarely found in the rectum. Large rectal GISTs in the narrow pelvis sometimes require extended abdominal surgery to obtain free resection margins, and it is a challenge to preserve sufficient anal sphincter and urogenital function. Here we present a 56-year-old male with a locally advanced juxta-anal non-metastatic GIST of approximately 10 cm in diameter. Therapy with imatinib reduced the tumour size and allowed partial intersphincteric resection (pISR). The patient underwent an electrophysiology-controlled nerve-sparing hybrid of laparoscopic and transanal minimally invasive surgery (TAMIS) in a multimodal setting. The down-to-up approach provided sufficient dissection plane visualisation and allowed the confirmed nerve-sparing. Lateroterminal coloanal anastomosis was performed. Follow-up showed preserved urogenital function and good anorectal function, and the patient remains disease-free under adjuvant chemotherapy as of 12 months after surgery. This report suggests that the TAMIS approach enables extraluminal high-quality oncological and function-preserving excision of high-risk GISTs.

INTRODUCTION

Gastrointestinal stromal tumours (GISTs) rarely occur in the rectum, comprising only ~3% of all anorectal mesenchymal tumours. Locally advanced rectal GISTs can be treated with abdominal surgery, including enclosed anterior resection, abdominoperineal resection and pelvic exenteration. Laparoscopic approaches have been reported in several cases.[12] However, it is proposed that this method be reserved for treatment of small GISTs at experienced centres.[3] Here we report a case in which a controlled nerve-sparing hybrid of laparoscopic and transanal minimally invasive surgery (TAMIS) was used to treat a locally advanced juxta-anal GIST, along with imatinib therapy.

CASE REPORT

During a screening colonoscopy, a 56-year-old male was diagnosed with a submucous rectal tumour. Digital rectal examination revealed a left-sided rigid mass compressing the anorectum. The anal sphincter showed normal resting and squeeze pressure. Transrectal ultrasound confirmed a huge semi-circumferential lesion, likely originating from the submucosal lower rectal third, displacing the prostate and protruding into the upper intersphincteric space. Magnetic resonance imaging (MRI) and computed tomography staging indicated a non-metastatic tumour of 10 × 6 × 6 cm3 [Figure 1]. Immunohistology showed that the tumour was a CD117+ CD34+ DOG1+ GIST with a Ki-67 labelling index of 40%. Mutation analysis revealed a KIT Exon 11 deletion (DNA sequence: c.1669_1674del; amino acid-sequence: p.W557_K558del).

Figure 1

MRI (T2) of the GIST before (a) and 4 weeks after neoadjuvant chemotherapy (b)

The patient's anorectal and urogenital function was uncompromised, and he strongly requested sphincter-preserving treatment. Neoadjuvant therapy was initiated with imatinib (400 mg/day). Four weeks later, MRI showed tumour reduction to 7 × 4 × 5 cm3. Ultrasound and digital examination confirmed free intersphincteric space 4 cm from the anal verge.

For total mesorectal excision using a laparoscopic approach, the peritoneal fold was opened circumferentially and nerve-sparing dissection continued down to the mid-rectum level above the GIST. A Lone Star Retractor (Cooper Surgical, Trumbull, CT, USA) was utilised for the transanal part, followed by partial intersphincteric resection (pISR) 3 cm from the anal verge at the dentate line level. After closing the oral rectal orifice, full-thickness rectal transection was performed to the GIST's dorsolateral lower edge, reaching the mesorectal plane. A multiport device (GelPOINT® path transanal platform; Applied Medical, Rancho Santa Margarita, CA, USA) was inserted. CO2 was continuously insufflated. Transanal dissection was achieved using LigaSure™ (Medtronic, Minneapolis, MN, USA) in the “down-to-up” direction under endoscopic visualisation in the holy plane, considering the extramesorectal portion of the GIST and nerves. Intraoperative neurostimulation confirmed functional nerve-sparing according to cystomanometry and internal anal sphincter electromyography responses. The specimen was removed through a port-sided mini-laparotomy following hand-sewn lateroterminal coloanal anastomosis for ostomy creation.

Histopathology revealed a ypT3, ypN0 (0/7), cM0, R0 situation with a Ki-67 labelling index of less than 5%. Three years of adjuvant therapy was recommended. The patient was discharged 8 days after surgery and has now been followed up for 12 months. The International Prostate Symptom Score revealed very good urinary function. Anal sphincter tone was unchanged, and the patient showed good faecal continence after regular stoma closure (Wexner score of 3 at 12-month follow-up). The low anterior resection syndrome (LARS) score indicated minor symptoms. At the last follow-up, the International Index of Erectile Function showed that sexual function was still reduced.

DISCUSSION

In four cases of lower rectal GIST, imatinib has been used to reduce tumour size (median, 5 cm; range, 1-5 cm), followed by successful laparoscopic-assisted pISR.[12] In a recently published series, five of 19 cases (26%) involved very large rectal GISTs of ≥10 cm in diameter.[3] In the present case, although neoadjuvant therapy led to substantial tumour shrinkage, it still appeared that it would be difficult to achieve clear margins and good functional results with laparoscopic surgery. Examination after 4 weeks showed a disturbing smooth tumour texture, leading to cessation of neoadjuvant treatment due to the perforation risk, particularly during surgery. Because pISR seemed possible, minimal access surgery was planned with the patient's informed consent. The fairly new TAMIS approach[4] enabled laparoscopic-assisted extraluminal high-quality oncological excision of the large juxta-anal GIST en bloc with the complete mesorectum [Figure 2]. Analogous to previous findings in rectal cancer surgery,[5] the down-to-up approach enabled sufficient visualisation and electrophysiologically confirmed nerve-sparing even in the narrow male pelvis.

Figure 2

Transanal view of the “no man's land” behind the prostate gland and seminal vesicles before (a) and after hybrid TAMIS-TME en bloc with the GIST (b)

In extremely rare cases of large rectal GISTs, the presently described laparoscopic-assisted TAMIS approach can be considered as a radical organ- and function-preserving option.

Financial Support and Sponsorship

Nil.

Conflicts of Interest

There are no conflicts of interest.