Oncological outcomes for transanal total mesorectal excision
Review Article

Oncological outcomes for transanal total mesorectal excision

Caterina Foppa1, Antonio Luberto1, Antonino Spinelli1,2

1Division of Colon and Rectal Surgery, Humanitas Clinical and Research Hospital, Rozzano, Milan, Italy; 2Department of Biomedical Sciences, Humanitas University, Rozzano, Milan, Italy

Contributions: (I) Conception and design: All authors ; (II) Administrative support: None; (III) Provision of study materials or patients: A Spinelli; (IV) Collection and assembly of data: C Foppa, A Luberto; (V) Data analysis and interpretation: All authors ; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors.

Correspondence to: Antonino Spinelli, MD, PhD. Humanitas Clinical and Research Hospital, Division of Colon & Rectal Surgery, Department of Surgery, Via A. Manzoni 56, 20089, Rozzano, Milan, Italy. Email: antonino.spinelli@hunimed.eu.

Abstract: Total mesorectal excision (TME) has become the gold standard technique for rectal cancer surgery with curative intent. Advantages in technology and surgical innovation lead to the introduction of minimally invasive techniques including laparoscopic, robotic and, more recently, transanal TME (TaTME). The concept of TaTME has been proposed to overcome the technical challenges encountered with the transabdominal approaches (open, laparoscopic, robotic) in the most difficult cases (obese, male patients with mid-low rectal cancer and a narrow, radiated pelvis and bulky mesorectum). Additionally, it has been recently claimed that TaTME offers at least 3 oncological advantages: (I) a longer distal resection margin (DRM), (II) a decreased rate of positive circumferential resection margin (CRM), (III) improved quality of TME. However, the oncological outcomes of TaTME compared to those of laparoscopic and robotic TMEs, remain controversial. Hence, a review of all the literature examining oncological outcomes after TaTME was performed. Two reviewers independently conducted a search of electronic databases (PubMed, MEDLINE, Cochrane Library). The last search was performed on August, 30th 2019. After the initial screen of 326 articles, 32 papers were selected for review, of these 19 were comparative studies and 1 a randomized controlled trial. TaTME resulted to provide oncologic outcomes at least comparable with the other minimally invasive approaches (laparoscopic, robotic) and seems to be associated with a lower rate of CRM involvement and TME incompleteness when compared to the laparoscopic, robotic, open approaches. Scarcity of data and short follow-up time made it impossible to draw conclusions on long-term oncologic outcomes. Hopefully, the COLOR III multicenter RCTs will shed a light on short- and long-term oncologic outcomes after TaTME.

Keywords: Transanal; total mesorectal excision (TME); laparoscopic; robotic; oncologic outcomes

Received: 14 September 2019; Accepted: 25 November 2019; Published: 30 June 2020.

doi: 10.21037/dmr.2019.12.01

Introduction

Total mesorectal excision (TME) has become the gold standard technique for rectal cancer surgery with curative intent (1). Circumferential resection margin (CRM), distal resection margin (DRM) and quality of TME are the main histopathology metrics directly affecting local recurrence (LR) and cancer-specific survival rates (2).

Advantages in technology and surgical innovation lead to the introduction of minimally invasive techniques including laparoscopic, robotic and, more recently, transanal TME (TaTME).

Obese, male patients with mid-low rectal cancers constitute a well-known challenge to low anterior resection with TME brought into even sharper relief when attempted laparoscopically. There are concerns that such patients with a narrow, radiated pelvis and bulky mesorectum may currently be undergoing sphincter-sparing resections with an involved CRM, a poor quality TME, or even an unnecessary abdominoperineal resection (APR). The concept of TaTME has been proposed to overcome the technical challenges encountered with the transabdominal approaches (open, laparoscopic, robotic) in these more difficult cases.

Recent randomized controlled trials (3-6) and comparative studies (7-8) have reported similar short- and long-term oncological outcomes among open, laparoscopic and robotic approaches. It has been recently claimed that TaTME offers at least three oncological advantages: (I) a longer DRM thanks to the distal transection under direct visual control, (II) a decreased rate of positive CRM, (III) improved quality of TME. However, the oncological outcomes of TaTME compared to those of laparoscopic and robotic TMEs, remain controversial.

The aim of this review was to evaluate TaTME oncological outcomes.

Methods

A review of the literature was performed searching in PubMed, MEDLINE, and Cochrane Library until August 30th, 2019. Two reviewers (CF, AL) independently conducted a search on electronic databases (PubMed, MEDLINE, Cochrane Library) using the following search headings: (“laparoscopic TME” OR “lapTME”) AND (“TaTME”) OR (“robotic rectal surgery”); (“transanal TME”) OR (“taTME”) OR (“Transanal Total mesorectal Excision”); (“transanal” OR “transanal endoscopic microsurgery”) OR (“transanal minimally invasive surgery”) OR (“natural orifice transluminal endoscopic surgery”) OR (“NOTES”) AND (“Tatme oncological outcomes”).

The reference lists provided by the identified articles were additionally hand-searched to prevent article loss by search strategy. This method of cross-references was continued until no further relevant publications were identified. Inclusion criteria were prospective, retrospective, randomized, comparative studies about TaTME for rectal cancer. Exclusion criteria were: abstracts, letters, editorials, technical notes, expert opinions, reviews, meta-analysis, studies reporting benign pathologies, studies in which the outcomes and parameters of patients were not clearly reported, studies in which it was not possible to extract the appropriate data from the published results, overlap between authors and centers in the published literature, studies with inappropriate number of patients (<10); non-English language papers.

The literature search yielded 326 papers, after the filtering, 32 articles were selected. The process is listed in Figure 1.

Figure 1 Flow diagram of literature search.

Results

Among the 32 selected articles 13 were case series (9-21) and 19 comparative studies (22-40), of these one was a RCT (22). Year of publication ranged from 2014 (22-36) to 2019 (12,23,40). Mean distance of tumor from the anal verge was reported in 17 studies (10-12,17-20,22,26-28,34-38,40) and ranged from 2 (34) to 8 cm (36) for TaTME and from 1.5 (34) to 7 cm (26) in LapTME. Table 1 gives a detailed overview of the selected studies.

Table 1

Studies overview

Reference Year Country Study design TaTMe (n) Lap TME (n) RobTME (n) OpTME (n) Mean distance from anal verge (cm)
Abdelkader et al. (9) 2018 Egypt Case series 25
Buchs et al. (10) 2016 United Kingdom Case series 40 3 (0–10)
Burke et al. (11) 2016 United States Case series 50 4.4 (3.0–5.5)
De Rosa et al. (12) 2019 Italy Case series 12 6.25 (3.5–10)
de Lacy et al. (13) 2018 Spain Case series 186
Hüscher et al. (14) 2016 Italy Cases series 102
Kang et al. (15) 2015 China Cases series 20
Lacy et al. (16) 2015 Spain Cases series 140
Muratore et al. (17) 2015 Italy Cases series 26 4.4 (3–6)
Park et al. (18) 2018 Korea Cases series 49 6.3±2.2
Penna et al. (19) 2017 United Kingdom Cases series 720 3.0 (0–11)
Rottoli et al. (20) 2015 United Kingdom Cases series 11 5 (2–7)
Veltcamp et al. (21) 2016 Netherlands Cases series 80
Denost et al. (22) 2014 France Comparative RCT 50 4 (2–6)
50 4 (2–6)
Detering et al. (23) 2019 Netherlands Comparative 396 396
Fernández-Hevia et al. (24) 2015 Spain Comparative 37 37
Kanso et al. (25) 2015 France Comparative 51 34
Law et al. (26) 2018 Hong Kong Comparative 40 5 (2–10)
40 7 (2–15)
Lee L et al. (27) 2018 Multicenter Comparative 226 370 5.6 (2.5)
Lee KY et al. (28) 2018 Korea Comparative 26 6.1±1.63
36 5.2±1.99
Lelong et al. (29) 2016 France Comparative 34 38
Mege et al. (30) 2018 United States Comparative 23 34
Perdawood et al. (31) 2018 Denmark Comparative 100 100 100
Perez et al. (32) 2017 Germany Comparative 55 60
Persiani et al. (33) 2018 Italy Comparative 48 57
Roodbeen et al. (34) 2018 Multicenter Comparative 41 2.0 (0.0–4.0)
41 1.5 (0.0–3.0)
Rubinkiewicz et al. (35) 2018 Poland Comparative 35 2.9±1.17
35 3.19±1.47
Velthuis et al. (36) 2014 Netherlands Comparative 25 8
25 6
Caycedo-Marulanda et al. (37) 2018 Canada Comparative 43 6.80±2.09
Chang et al. (38) 2018 Taiwan Comparative 23 4.3±1.4
23 5.9±1.1
Chen CC et al. (39) 2016 Taiwan Comparative 50 100
Chen YT et al. (40) 2019 Taiwan Comparative 39 4.3±1.4
64 5.8±1.2
23 5.6±1.3

TME, total mesorectal excision; TaTME, transanal TME; LapTME, laparoscopic TME. RobTME, robotic TME; OpTME, open TME.

Number of harvested nodes

Twenty-six out of 31 studies reported the mean number of harvested nodes which ranged from 10.7 (28) to 26.45 (26) in TaTME; from 11 (28) to 26.69 (26) in laparoscopic TME (LapTME) and from 13 (17) to 16.8 (18) in robotic TME (RobTME). The mean number of harvested nodes after open TME (OpTME) was reported in 1 study and was 23.5±8.2 (7).

One (31) of the 16 comparatives studies (22,24-34,36,38-40) reported statistically significant difference in number of harvested nodes beetwen Ta- and OpTME but no difference was reported when Ta- and LapTME were compoared. Table 2 shows the results in details.

Table 2

Oncological outcomes

Reference Pts Surgical technique Harvested nodes Distal margin distance (cm) CRM + (%) CRM (mm) Complete TME Nearly complete TME Incomplete TME
Abdelkader et al. (9) 25 TaTME 1.9±1.1 2 (8) 22 (88) 2 (8) 1 (4)
Buchs et al. (10) 40 TaTME 20±9.7 2.69±2.22 2 (5) 10.8±9.5
Burke et al. (11) 50 TaTME 18.0 (12.0–23.8) 1.0 (0.5–1.7) 2 (4) 7.0 (2.5–15.0) 36 (72) 13 (26) 1 (2)
De Rosa et al. (12) 12 TaTME 13.6±6.6 2.08±1.42 16.1±7.6 12 (100) 0 0
de Lacy et al. (13) 186 TaTME 14.0 2.1 7 (10.1) 15.4 178 (95.7) 3 (1.6) 2 (1.1)
Hüscher et al. (14) 102 TaTME 20±11.7 3.71±2.85 37.1±28.5 99 (97.1) 3 (2.9)
Kang et al. (15) 20 TaTME 1.0 (0.5–2.5) 0 (0) 12 (3–19) 18 (90) 2 (10%) 0
Lacy et al. (16) 140 TaTME 14.7±6.8 9 (6.4) 22±4 136 (97.1) 3 1
Muratore et al. (17) 26 TaTME 1.9 11.1 23 (88.4)
Park et al. (18) 49 TaTME 19 (8–42) 2.4±0.19 4 (8.2) 35 (71.4) 12 (24.5) 2 (4.1)
Penna et al. (19) 720 TaTME 16.5±9.2 1.9±1.43 14 (2.4) 9.19±8.6
Rottoli et al. (20) 11 TaTME 21.7 (11–50) 1 (0.5–2.0) 5 (1–20) 0
Veltcamp et al. (21) 80 TaTME 14 (6–30) Positive DRM: 0% 2 (2.5)£ 71 (88) 7 (9) 2 (3)
Denost et al. (22) 50 TaTME 17 (2–30) 1 (0–3)§ 2 (4) 7 (0–20) 35 (70) 9 (18) 6 (12)
50 LapTME 17 (9–40) 1 (0.1–3)§ 9 (18) 5 (0–20) 31 (62) 13 (26) 6 (12)
Detering et al. (23) 396 TaTME 17 (4.3)
396 LapTME 16 (4.0)
Fernández-Hevia et al. (24) 37 TaTME 14.3±6 2.8±1.8 0 11±0.6 35 (95) 2 (5) 0
37 LaTME 14.7±6 1.7±1.3 0 12±0.9 34 (92) 2 (5) 1 (3)
Kanso et al. (25) 51 TaTME 15±8 1.2±0.9^ 5 (10) 7±6
34 LapTME 13±7 1.8±1.5^ 3 (9) 7±6
Law et al. (26) 40 TaTME 13 2 (0.5–5) 0 (0)
40 RobTME 13 2 (0.5–6) 2 (5)
Lee L et al. (27) 226 TaTME 16.1 1.69! 12 (6.3) 209 (92.5) 15 (6.6) 2 (0.9)
370 RobTME 16.8 1.51! 21 (6.2) 356 (95.4) 14 (3.8) 3 (0.8)
Lee KY et al. (28) 21 TaTME 10.7±6.28 2.2±1.28 1 (4.8) 19 (90.5) 2 (94.5) 0
24 RobTME 13.6±6.29 1.9±1.06 2 (8.3) 24 (100) 0 0
Lelong et al. (29) 34 TaTME 14 (6–34) 2 (5.8) 19 (55.8) 15 0
38 LapTME 12 (4–25) 4 (10.5) 20 (52.6) 16 2
Mege et al. (30) 34 TaTME 14±10 Positive DRM TaTME 1 (3%) vs. LapTME 1 (3%) P=1 4 (12) 18 (53) 9 (27) 7 (21)
34 LapTME 14±8 2 (6) 27 (79) 3 (9) 4 (12)
Perdawood et al. (31) 100 TaTME 22.32±8.70# 2.22±1.27” 7 (7) 8.99±7.21 58 (58)& 28 (28)& 14 (14)&
100 LapTME 21.75±10.98# 2.40±1.51” 13 (13) 9.44±7.86 68 (68)& 12 (12)& 20 (20)&
100 OpTME 17.92±9.29# 3.47±2.35” 10 (10) 9.57±7.49 68 (68)& 15 (15)& 17 (17)&
Perez et al. (32) 55 TaTME 15 (8–55) 1.9 (0.8–3) 12 (5–20) 50 (91) 5 (9) 0
60 RobTME 15 (7–30) 3.1 (1.9–4.5) 19 (12–49) 53 (88) 7 (12) 0
Persiani et al. (33) 48 TaTME 12 (3–26) 2.5 (0.5–6) 0 40 (87) 4 (8.7) 2 (4.3)
57 LapTME 11 (3–26) 1.5 (0.5–4) 0 39 (84.8) 5 (10.9) 2 (4.3)
Roodbeen et al. (34)€ 41 TaTME 18 (13–26) 2 (1–4) 3 (7) 10 (4.2–12) 38 (92.7)
41 LapTME 14 (11–24) 2 (0.98–4.13) 2 (4.8) 5 (3–10) 21 (84.0)
Rubinkiewicz et al. (35) 35 TaTME Positive DRM 0 TaTME vs. 1 (2.8%) LapTME 1 (2.8) 31 (89) 4 (11) 0 (0)
35 LapTME 0 29 (83) 6 (17) 0 (0)
Velthuis et al. (36) 25 TaTME 14 (7–24) 2.3 (0.5–8) 1 (4)£ 13 (1.5–3) 24 (96) 1 (4%) 0
25 LapTME 13 (1–36) 2.5 (0–5.5) 2 (8)£ 12 (0–2.5) 18 (72) 2 (8%) 5 (20)
Caycedo-Marulanda et al. (37) 43 TaTME 24.81±9.90 1 (2.33) 36 (83.72) 7 (16.28) 0
Chang et al. (38) 23 TaTME 22.8±10.8 1.35±1.05 0 (0)
23 LapTME 19.5±8.6 1.55±1.05 4 (7)
Chen CC et al. (39) 50 TaTME 16.7±7.8 2.4±1.2 2 (4) 11.8±7.5
100 LapTME 17.4±8.9 1.5±0.9 10 (10) 11.1±7.7
Chen YT et al. (40) 39 TaTME 20.8±9.0 1.6±1.4 0*
64 LapTME 18.8±8.1 1.9±1.3 5 (7.8)*
23 OpenTME 23.5±8.2 1.6±0.9 3 (13)*

*, TaTME vs. LapTME P=0.08; TaTME vs. OpTME P<0.01; Lap TME vs. OpTME P=0.2; §, positive DRM TaTME 1 (2%) vs. LapTME 4 (8%) P=0.362; ^, positive DRM TaTME 4 (8%) vs. LapTME 0 P=0.25; !, positive DRM TaTME 4 (1.8%) vs. RobTME 1 (0.3%) P=0.051; #, TaTME vs. LapTME P=0.889; TaTME vs. OpTME P=0.003; LapTME vs. OpTME P=0.018; “, TaTME vs. LapTME P=0.995; TaTME vs. OpTME P<0.065; LapTME vs. OpTME P=0.052; positive DRM TaTME 0, LapTME 1, OpTME 1 P=0.604; &, TaTME vs. LapTME P=0.016; TaTME vs. OpTME P=0.082; LapTME vs. OpTME P=0.750; €, positive DRM TaTME 0 vs. Lap TME 3 (7%) P=0.241; £, positive CRM <2 mm. TME, total mesorectal excision; TaTME, transanal TME; LapTME, laparoscopic TME. RobTME, robotic TME; OpTME, open TME.

DRM

Twenty-five (9-15,17-20,22,24-28,31-34,36,38-40) out of 31 studies reported the DRM which ranged from 1 cm (3,10,14,29) to 2.8 cm (24) in TaTME. The mean length of DRM after LapTME was available in 10 (22,24,25,31,33-36,38-40) studies and ranged from 1 cm (10) to 2.5 cm (36). The mean length of DRM after RobTME was reported in 4 (26-28,32) articles and ranged from 1.5 cm (27) to 3.1 cm (32). DRM after OpTME was reported in 2 studies (31,40) and was 1.6 and 3.47 cm (31,40).

Five (6,25,27,31,32) out 18 (24,31-33,39) comparative studies reported statistically significant difference in mean length of DRM. Three studies reported significantly longer mean DRM after TaTME vs. Lap TME (6,25,27). One study (32) reported longer DRM after Rob TME vs. TaTME. Perdawood et al. (31) reported longer DRM when TaTME or LapTME where compared to OpTME, but no difference was reported between TaTME and LapTME. Six comparative studies (22,25,27,30,31,34) reported the DRM involvement rate which ranged from 0% to 8% in the TaTME and LapTME cases, DRM was involved in 0.3% of RobTME in the only study reporting this data (27). No statistically significant difference was reported among studies in DRM involvement rates. Table 2 shows the results in details.

CRM

CRM involvement after TaTME surgery were reported in 27 studies (Table 2). And ranged from 0% (15,24,26,33,38,40) to 12% (30) after TaTME, from 0% (24,33,35) to 13% (31) in 7 studies (22-25,29-31) reporting LapTME, from 5% (26) to 8.3% (28) in 3 studies reporting RobTME (26-28) and was 10% (31) and 13% (40) in 2 studies reporting OpTME (31,40). Three studies reported significantly lower CRM involvement rates in TaTME vs. LapTME (22,38,40) or OpTME (40). Among these 3 studies (22,38,40), one was a RCT (22) comparing the transanal and laparoscopic approach. The cut-off to define a positive CRM was 1 mm in 25 studies (9-11,13,15,16,18,19,22-31,33-35,37-40) and 2 mm in 2 studies (21,36). Eighteen studies (10-17,19,20,22,24,25,31,32,34,36,39) reported the CRM width in mm, of these 8 were comparative (22,24,25,31,32,34,36,39). CRM width ranged from 5 mm (20) to 37.1 mm (14) in TaTME, from 5 (22,34) to 12 mm (24,36) in LapTME. One study reported the width of CRM in the OpTME (31) and another in the RobTME (32). This last study (32) reported a statistically significant wider CRM in the RobTME vs. the TaTME group. Table 2 shows the results in details.

Quality of TME

Quality of TME according to Quirke (41) was evaluated in 23 studies (9,11-18,21,22,24,27-37) [12 comparative (22,24,27-36)]. Complete quality of specimen ranged from 53% (30) to 100% (12) after TaTME, from 52.6% (29) to 92% (24) in the 9 studies evaluating LapTME (22,24,29-31,33-37], from 88% (32) to 100% (28) in the 3 studies reporting RobTME (27,28,32) and was 68% in one study reporting OpTME (31). Incomplete quality of TME ranged from 0% (12,15,20,24,28,29,32,35-37] to 21% (30) in TaTME, from 0% (28,35) to 20% (31,36) in LapTME and was 0% in the 2 studies reporting RobTME (28,32) and 17% in one study reporting OpTME (31). Two (31,36) out of the 12 comparative (22,24,27-36) studies reported a statistically significant higher rate of complete TME with TaTME vs. LapTME. Table 2 shows the results in details.

Long-term survival

Eight studies (9,10,11,16,21,25,27,40) reported long term follow-up data, of these 3 were comparative (25,27,40). Follow-up time was reported in median (15.1–39 months) (11,25,27) or mean (15–28.6 months) (9,10,16). LR, DFS and OS rates after TaTME ranged from 0% (40) to 4.8% (27), from 63% (25) to 90.8% (16) and from 92.5% (10) to 100% (25) respectively. Chen et al. (40) reported a statistically higher DFS when TaTME and LapTME were compared to OpTME (P=0.01), no difference in DFS was reported when taTME was compared to LapTME (P=0.7). Table 3 shows the results in details.

Table 3

Long-term oncologic outcomes

Reference Patients Surg technique Follow-up (months) Local recurrence (%) DFS OS
Abdelkader et al. (9) 25 TaTME 28.6±5.9 (7–36) mean 1 (4) 22 (88)
Buchs et al. (10) 40 TaTME 6.5 mean 34 (85) 37 (92.5)
Burke et al. (11) 50 TaTME 15.1 (7–23.7) Median 2 (4) 41 (82)£
Lacy et al. (16) 140 TaTME 15±9.1 mean 1 (0.8) 119 (90.8) 136 (97.1)
Veltcamp et al. (21) 80 TaTME 30 2 (2.5)
Kanso et al. (25) 51 TaTME 39 (0–85) 32 (63) 51 (100)
34 LapTME Median 21 (62) 32 (93)
Lee et al. (27) 21 TaTME 20.1 1 (4.8)
24 RobTME 22 median 0 (0)
Chen YT et al. (40) 39 TaTME 24 0 (0) 2 (90)* 2 (97)
64 LapTME 3 (4.7) 2 (91)* 2 (89)
23 OpenTME 2 (8.7) 2 (65)* 2 (89)

*, TaTME vs. LapTME P=0.7; TaTME vs. Op TME P=0.01; LapTME vs. OpTME P=0.01; £, 2 patients already metastatic at diagnosis. TME, total mesorectal excision; TaTME, transanal TME; LapTME, laparoscopic TME.

Discussion

The gold standard treatment for mid-low rectal cancers is TME, which has been elucidated to optimize locoregional clearance (1) and to decrease LR rates (42).

Laparoscopic and robotic TME represent a leap forward in the treatment of rectal neoplasms, providing improved short-term and analogous long-term outcomes (3-8,43). However, performing an anterior rectal resection with a good quality TME is technically challenging, particularly with the laparoscopic approach, due to the tapering of the distal mesorectum and inadequate identification of the neurovascular bundle, and mainly because of the limited operative field leading to a difficult view and difficult placement of endoscopic staplers and mobilization in the deep pelvis. Aforementioned factors in combination with suboptimal anastomotic techniques evoke insufficiency of DRM, incompleteness of mesorectum and CRM involvement, with consequent LR. Previous RCTs (3,44) found a high involvement of CRM rate (7–12.1%) in laparoscopic TME. The ROLARR trial (8) found no statistically significant oncological or clinical advantage of RobTME over LapTME with positive CRM rates of 5.1% and 6.3% respectively. The “bottom-up” approach of TaTME was pioneered to minimize the limits of the “up-to-down” approaches. In fact, TaTME helps to clearly expose the anatomical plane and accurately determine the resection margin in a narrow pelvis, as well as a more direct approach to the most problematic aspects of the distal rectal dissection, thus in turn producing better perioperative results, enhanced oncological quality as well as superior nerve-sparing (45,46).

This review was focused on the quality of TME, DRM and CRM as they are the measures of the TME quality and are deemed as major predictive factors for rectal resections affecting LR and survival (1,41,47). TaTME resulted to provide good oncologic outcomes and seems to be associated with a lower rate of CRM involvement and TME incompleteness when compared to the abdominal approaches (laparoscopic, robotic, open). These results were also reported by two recent meta-analysis comparing one Ta- and LapTME (48) and the other Ta-, Rob- and OpTME (49). Ma et al. (50) in their systematic review and meta-analysis reported longer CRM, less positive CRM rates and a higher rate of complete specimens when TaTME was compared with LapTME. Another meta-analysis analysing Ta- and RobTME (51) reported lower pooled CRM involvement rates for TaTME, although this result was not statistically nor clinically significant. Accordingly, the only RCT (22) comparing Ta- and LapTME reported a significantly lower CRM involvement rate with the bottom-up approach.

It is undeniable that the core value of TaTME lies in achieving an adequate DRM as the rectal transection is under direct visual control. Nonetheless, there was no significant difference among studies in terms of DRM as reported also by a recent meta-analysis (51). Surprisingly, one study (32) reported significantly lower DRM and CRM in the TaTME group when compared to the robotic approach although there were no differences among the two groups in tumor size and site, neoadjuvant therapy or Quirke’s mesorectal grading. However, a possible institutional bias with different pathological assessment of the specimens may have affected the results. For this reason, result pertaining DRM should be interpreted cautiously as it is important to point out the heterogeneity of the published studies in terms of tumor size and tumor stage and mainly of tumor location (48,50,51).

A study by Perdawood et al. (52) aiming to compare 29 TaTME to 29 LapTME cases with defects in the retrieved specimen reported a significantly longer DRM in the TaTME group (33.45+14.5 vs. 25.41+11.16; P=0.048). Interestingly, the ratio of defects below the peritoneal reflection was significantly lower in the TaTME group suggesting that TaTME has the potential to improve rectal cancer surgery through improvement of dissection in the lower rectum.

It is important to note that most of the reported studies included the surgeon’s learning curve and despite this, results were very promising.

Most studies have reported only short-term outcomes, which reflects the novelity of TaTME. Whether this new approach has similar oncological outcomes in terms of LR, DFS and cancer specific survival will require further studies in prospective trials that compare TaTME with laparoscopic or robotic TME over substantial follow-up period.

As TaTME is adopted increasingly by surgeons, patients’ selection criteria will be crucial to continue to animate the debate. Hopefully, the TaTME international registry as well as COLOR III RCT (53) with its strict selection criteria will give definitive answers on short- and long-term oncologic outcomes after TaTME (vs. lapTME).

Conclusions

TaTME is an oncologically safe and effective technique, resulting in at least comparable oncologic outcomes when compared to the abdominal approaches. Standardization of surgical technique, implementation in daily practice as well as strict selection criteria are required to further clarify the role of TatME in the treatment of rectal cancer. Hopefully, the COLOR III multicenter RCTs will shed a light on short- and long-term oncologic outcomes after TaTME.

Acknowledgments

Funding: None.

Footnote

Provenance and Peer Review: This article was commissioned by the Guest Editors (Janindra Warusavitarne and Roel Hompes) for the series “TaTME” published in Digestive Medicine Research. The article has undergone external peer review.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/dmr.2019.12.01). The series “TaTME” was commissioned by the editorial office without any funding or sponsorship. AS acted as teacher/consultant/speaker for Ethicon and Takeda. The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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doi: 10.21037/dmr.2019.12.01
Cite this article as: Foppa C, Luberto A, Spinelli A. Oncological outcomes for transanal total mesorectal excision. Dig Med Res 2020;3:17.

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