Introduction

Rectal cancer treatment has come a long way from initial days of abdominoperineal resection (APR) to low anterior resection (LAR) and ultra-low anterior resection (uLAR) and transanal total mesorectal resection (TaTME).1 All these procedures involve proctectomy and have certain morbidity and very occasionally mortality associated with them. The change in the bowel functions and episodes of incontinence and LAR syndrome often lead to unhappy patients. There has been a shift toward organ preservation over the past many years, and the watch and wait policy is slowly becoming popular in select patients who have complete clinical response to neoadjuvant chemotherapy and radiation.

Transanal minimally invasive surgery (TAMIS) is an organ-preserving surgery for rectal cancer. It has both curative and diagnostic implications (Table 1).2 As per the National Comprehensive Cancer (NCCN) guidelines, TAMIS is indicated in T1 rectal cancer with favorable pathology—well or moderately well-defined adenocarcinoma, no lymphovascular invasion, and size ≤3 cm. In such situations, TAMIS is curative.3 The incidence of lymph node metastasis in T1 cancer is 6%.4 If post TAMIS there is upstaging of the disease to T2 or deeper layers of sub mucosa (sm2 or sm3) then further trans abdominal resection is warranted.5 Patients are preoperatively counseled about it before they undergo TAMIS. TAMIS was first reported in a series of just six patients by Atallah in 2010 from Florida.6 It gained rapid popularity throughout the world and replaced conventional transanal excision and transanal endoscopic microsurgery (TEM) in many places. Due to its simplicity of technique and use of conventional laparoscopic instruments, it was adopted more enthusiastically by colorectal surgeon than TEM. TEM was described by Herald Beus from Germany in 1985.7 But its adaptation was slow mainly due to its rigid platform, specialized instruments, and high equipment cost. A slow learning curve has also been reported for TEM. In contrast, TAMIS gives a 360-degree view of the rectal lumen and uses conventional laparoscopic instruments.1

Technique

Preoperative workup is done by performing a full colonoscopy to rule out any synchronous lesions. A magnetic resonance imaging (MRI) of the pelvis with or without endo-anal ultrasound and a contrast-enhanced computed tomography (CECT) of the chest, abdomen, and pelvis are performed to rule out any metastatic disease. A bowel preparation is done preoperatively and intravenous (IV) prophylactic antibiotics are administered. The transanal platform is inserted in the anal canal and secured with silk sutures. Pneumorectum is created by connecting the CO₂ insufflator to the gel point path and a 5-mm 30-degree telescope is used to visualize the lesion. Conventional or specially designed laparoscopic instruments are used to perform the excision. An L-shaped hook is used to score the lesion 1 cm from the lesion toward the healthy mucosa side (Fig. 1). This is followed by full-thickness excision exposing the perirectal fat (Fig. 2). The specimen is then extracted and oriented for pathological examination (Fig. 3). The rectotomy is sutured or left open depending upon the surgeon's preference (Figs. 4, 5).8

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Fig. 1: Scoring.

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Fig. 2: Full-thickness dissection.

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Fig. 3: Resected specimen with markings.

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Fig. 4: Closing the defect with 3–0 V-Loc suture.

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Fig. 5: Final appearance after closure.

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Indications

T1N0M0 rectal cancers are located in the rectum. These should be well or moderately well differentiated with no lymphovascular invasion. Swedish rectal cancer registry results reported nodal metastasis for T1 rectal cancers up to 12% with adverse features, but if there are no adverse features, then it is 6%. Poor differentiation, lymphovascular invasion, and invasion of the submucosa greater than 1 mm are predictive factors for nodal metastasis. If any of these factors are present post-TAMIS, then a formal proctectomy is indicated. Cancer-specific survival compared with radical resection is not different for T1 cancer patients who underwent TAMIS compared with patients who underwent radical resection.910

TAMIS has also been used for T2 or T3 rectal cancers as a palliative procedure for symptom relief where patients refuse surgery or they are not medically fit for transabdominal resection. This is an oncologically inferior procedure but serves its purpose in selected patients.21112 Although the GRECCAR 2 trial advocated local excision in select patients having a small T2–T3 low rectal cancer with good clinical response after chemoradiation, it has not been incorporated into any major guidelines like NCCN

Preoperative Staging

This includes a full physical examination with digital rectal examination with rigid proctoscopy to determine the distance of the lesion from the anal verge. A full colonoscopy is done to check for any synchronous lesions. The location of the lesion is described as per its location and the percentage of the rectal circumference it occupies. An endoanal USG is more helpful in determining the accuracy of T1 or T2 lesions. MRI is more helpful in assessing the lymph node involvement. A CECT of the chest, abdomen, and pelvis is undertaken to rule out any systemic metastasis.

Follow-Up

As per NCCN guidelines, a physical examination, rigid proctoscopy, and serum carcinoembryonic antigen (CEA) levels should be performed every 3 months for the first 2 years. A positron emission tomography (PET) scan should be performed after 1 year; thereafter, it should be performed yearly for 5 years. A full colonoscopy is indicated after 1 year; if it is normal, then it should be done after 3 years, followed by every 5 years to detect any metachronous lesions.3

Outcomes

There are certain complications associated with TAMIS like bleeding, urinary retention, scrotal emphysema in males, extraperitoneal wound dehiscence, rectal stenosis, and transient fecal incontinence. Rectovaginal fistula has been reported in females Bleeding is usually controlled by examination under anesthesia and suturing or packing of the rectal defect. Most of the patients go home the next day of surgery or within 12 hours. Mortality is unreported.1314

Current Evidence

Currently TAMIS is indicated in early rectal cancers where there is low risk of lymphatic spread. In this situation, it is usually curative. Patients who require palliation in case of stage 4 rectal cancer or patients who are very old and frail who need local palliation can be benefited by TAMIS. The specimen fragmentation rate is reported approximately 4%. The reported recurrence after TAMIS is approximately 2.7%.2

Future Trends

The TESAR Dutch trial is underway to determine the outcomes after local excision for T1 with poor features or T2 low rectal cancers with low-risk features, comparing completion TME versus adjuvant chemoradiation. The STAR-TREK trial is underway to determine whether TME versus watch and wait versus local excision is more effective for T1–T3b N0 rectal cancers following either long course chemoradiation or short course radiotherapy. Robotic TAMIS has been reported by some authors to be comparable with conventional TAMIS but with additional costs. Intraoperative and mass spectrometry and immunofluorescence may improve assessment of margins in real time.151617

Conclusion

TAMIS is a good operation and results in better quality and intact specimen for low-risk and small rectal cancers. It has good patient acceptance and is usually well tolerated. Trials are underway to determine whether it has a role in advanced stages of rectal cancer. TAMIS can also be used as a salvage operation in symptomatic high-risk patients who cannot undergo or are unfit for transabdominal resection.