In this observational cohort study, we compared clinical and oncological outcomes between TaTME and LaTME. Using PSM analysis, these techniques' median follow-up period was 54 months and 65 months, respectively. Before PSM, the 2-year LR rate for TaTME and LaTME was 4.5% and 6.5% in each group, while after the analysis, it was 5.9% for both groups. These results tie in well with previous studies. A few examples, the 2-year LR rates for LaTME of the ALaCaRT and ACOSOG trials were 5.4% and 4.6%, respectively. Furthermore, the 3-year LR rate for LaTME in the COLOR III trial was 5.0% [4, 6, 7], and the 2-year LR rate for TaTME was 4.5%, comparable with established conventional techniques. However, one patient in the TaTME group developed multifocal recurrence in early phase after neoadjuvant chemotherapy. The patient had a threatened mesorectal fascia in the baseline MRI after chemotherapy with an anterior lesion located 4 cm from the anal verge. Additional chemoradiotherapy and an abdominoperineal resection should be considered in this case. Roodbeen et al. informed a 2-year LR rate of 4.8% with a unifocal LR pattern in 99 of 103 patients (96%). The independent risk factors for LR were male sex, threatened resection margin on baseline MRI, pathologic stage III cancer, and a positive circumferential resection margin on final histopathology from the data of an international registry (a total of 2,803 patients) [24]. Therefore, a more intensive strategy like total neoadjuvant therapy should be considered for patients of male sex with threatened resection margin on baseline MRI (29, 30).
Operative outcomes differ in terms of the operative time, the rate of stapled anastomosis, the rate of conversion to open surgery, and the rate of protective loop ileostomy. The operative time was significantly shorter, and conversion to open surgery was null, as in previous reports for the TaTME group [31–33]. The conversion rate in large clinical trials, including ALaCaRT, ACOSOG, and COLOR II trials, ranged from 9 to 16% [4, 6, 7]. There are surgical difficulties during laparoscopic rectal cancer surgery for patients with obesity, narrow pelvis, male sex, and bulky tumors. TaTME via two-teams approach reduces these surgical difficulties, resulting in a shorter operative time and a minimum conversion rate. The rate of protective loop ileostomy was significantly higher in the TaTME group and seemed to be caused by the increase in hand-sewn anastomosis to preserve the sphincter resection and the difficulty of the single stapling technique for low anterior resection. The postoperative complications (Table 2), including anastomotic leak, were comparable between the two groups. Moreover, these results are acceptable when compared to the International TaTME Registry: the informed rate of postoperative complications and anastomotic-related morbidities are 35.4% and 19.8%, respectively [20]. We attribute these complications to the fact that TaTME was performed along the fascia in the loose areolar tissue facilitated by proper traction of the rectum through enhanced transanal visualization of the surgical plane.
TME for rectal cancer is the gold standard technique accepted worldwide [1–3]. Anterior retraction of the rectum creates loose areolar tissue between the mesorectal fascia and the endopelvic fascia dorsolaterally [2]. The basic principle of TME is sharp dissection within the holy plane [2]. TaTME potentially provides improved visualization of the deep prostate or vaginal plane with the acquisition of intact specimens and a low rate of CRM involvement [15–18]. In the present study, RM was 1.1% and 2.2% in the TaTME and LaTME groups, respectively, before PSM. We focused on the surgical technique of TaTME considering the embryology along the fascia to perform an adequate TME. This technique can recognize the holy plane through enhanced transanal visualization. The pelvic nerves are preserved by pursuing an intact layer via fascial separation. However, because pneumodissection can occur deep to the nerve plexus with TaTME, the surgeon must be alert to the possibility of going too laterally, which could lead to dissection in a plane deep to the parietal pelvic fascia and resultant inadvertent pelvic nerve injury [34].
Taking into consideration our results, safely TaTME application is crucial. A formal structured training pathway should be completed to implement the technique in clinical practice [35], including self-learning, cadaver workshops, mentorship of initial 5–10 TaTME cases, and independent practice [36]. A detailed framework for a structured TaTME training curriculum that promotes competent performance is also essential to ensure that the introduction of a new technique occurs in a safe and controlled manner to protect both the patient and the surgeon [35–37]. Discussion of case selection with a mentor or supervisor, optimization of the technique, and inclusion of TaTME data into the international registry, are also recommended to achieve quality control of the method [35–37].
Our study has some limitations. Despite using PSM to decrease the selection bias, this cannot be entirely excluded because the study is retrospective and with a small number of patients. Larger-scale randomized controlled trials are necessary to optimize this challenging approach's benefits and potential indications. Also, it should be noted that the mean duration of the postoperative hospital stay in our institution was 14 days, and we attribute postoperative complications to this extended time. In contrast, we consider acceptable the postoperative morbidity rate and the 30-day readmission rate. Lastly, the resultant mean duration of surgery was long due to careful dissection during TaTME to avoid visceral or parietal injury with minimal blood loss. Practitioners still need to gain further experience and polish the necessary technical skills. The final limitation of this study is that the CRM was assessed as the RM according to the Japanese Classification of Colorectal Carcinoma [26]. Possibly, the results do not adequately reflect the CRM since all mesenteric lymph nodes were retrieved after surgery and fixed in formalin.