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Page 6 of 8 Toma et al. Mini-invasive Surg 2018;2:21 I http://dx.doi.org/10.20517/2574-1225.2018.24

alternative to our LECS procedure for large NADENs.

In the literature [10-15] , a total seven authors reported a series of LECS for NADENs where the lesions were
treated by either ESD and subsequent laparoscopic repair or endoscopy-assisted laparoscopic full-thickness
resection and repair without any serious intra- and postoperative complications, corresponding to our
results [Table 3]. In those reports, surgery was occasionally performed for adenocarcinomas confined in
the mucosa, but no tumor recurrence was noted in the postoperative course, revealing the feasibility of the
indication of LECS for NADENs. Regarding the size of NADENs successfully treated with LECS, the mean
diameter ranged from 13.3 to 22 mm [Table 3]. From our experience of only one conversion involving a tu-
mor that was 54 mm in diameter, LECS might be accomplished for NADENs within approximately 30 mm
in diameter and at least 10 mm away from Vater papilla.

Our LECS procedure for NADENs is consistent with the previous reports, demonstrating ESD and sub-
sequent laparoscopic repair in the treatment of NADENs [13,14] . Complete resection of the lesions by ESD
without micro-perforation theoretically enables the avoidance of tumor dissemination in the peritoneal
cavity, where the precise preoperative evaluation of the depth of NADENs is inevitable. Furthermore,
postoperative analysis of pathological results is critical, given that additional surgery could be required in
cases involving margins or vertical invasion beyond the submucosal layer of malignant lesions. Long-term
follow-up for patients with malignant results are warranted to verify the oncological feasibility of LECS for
NADENs.

Exposure of the epithelial injury in the duodenum to bile and pancreatic juice impairs tissue regenera-
tion [18,19] . Consequently, repair of the mucosal defect resulting from ESD is critical for the prevention of
postoperative complications in LECS for NADENs. Compared with previous reports [13,14] , our procedure
for LECS for NADENs is novel in terms of the repair procedure after ESD consisting of the combination of
laparoscopic hand-sewn seromuscular suture and endoscopic clipping, enabling the closure of the mucosal
defect from both inside and outside the duodenum [Figure 3]. The anticipation of laparoscopic hand-sewn
seromuscular sutures contributed to the reduction of the mucosal defect and therefore facilitated subse-
quent endoscopic clipping, compared with immediate clipping after ESD. In our results, immediate or
delayed bleeding and perforation did not occur, revealing the feasibility of repair using LECS for NADENs.
The future prevalence of robotic surgery may facilitate the laparoscopic suturing in LECS for NADENs.

[20]
Ojima et al. recently reported the operative results of LECS superior to ESD for the treatment of
NADENs in the comparative study. They showed the statistically decreased incidence of any postopera-
tive complications including bleeding and perforation in LECS, demonstrating LECS contributed to the
improvement in the safety during and after ESD for the treatment of NADENs. To date, clinical data re-
garding LECS for NADENs derived from the short-term outcomes. Therefore, it should be reminded the
long-term oncological outcomes remain to be verified for the establishment of LECS for NADENs. For the
moment, the indication of LECS for NADENs requires deliberate consideration before the surgery and
should be limited to NADENs at low-risk of biological aggressiveness.

In conclusion, LECS is a promising procedure of choice in the treatment of NADENs, facilitating early
resumption of both food intake and full daily activity in the postoperative course. Further accumulation
of clinical evidence is warranted for the establishment of the treatment strategy and obtaining long-term
results of LECS for NADENs.

DECLARATIONS
Authors’ contributions
Study concept and design, manuscript preparation: Toma H, Haraguchi K, Eguchi T