Page 29 - Read Online

Page 6 of 9 Shirakawa et al. Mini-invasive Surg 2020;4:33 I http://dx.doi.org/10.20517/2574-1225.2020.30

Table 2. Surgical findings
Variable Pre-standardization group (n = 91) Post-standardization group (n = 83) P value
Intraoperative findings
Thoracoscopic operative time [min (IQR)] 232.0 (202.8-264.0) 209.0 (176.0-235.0) < 0.001 a
Blood loss [mL (IQR)] 200 (100-330) 200 (105-400) 0.764 a
Number of dissected No. 106 lymph nodes (IQR) 11 (8-15) 10 (8-13) 0.137 a
Conversion to thoracotomy (%) 0 (0) 0 (0) 1.000 b
Postoperative findings
Total morbidity [≥ Grade II (%)] 48 (52.7) 37 (44.6) 0.250 b
Respiratory complications [≥ Grade II (%)] 15 (16.3) 14 (16.9) 0.946 b
Recurrent laryngeal nerve palsy [≥ Grade I (%)] 18 (19.8) 8 (9.6) 0.061 b
Anastomotic leakage [≥ Grade II (%)] 7 (7.7) 9 (10.8) 0.472 b
ICU stay [days (IQR)] 6 (5-7) 6 (5-6) 0.742 a
Postoperative hospital stay [days (IQR)] 21 (17-26) 22 (17-27) 0.782 a
In-hospital mortality (%) 0 (0) 0 (0) 1.000 b
a Mann-Whitney test, χ test. Complications are described according to the Clavien-Dindo classification [24] . IQR: interquartile range; ICU:
b 2
intensive care unit

Clinical outcomes
There were no significant differences between the two groups in the amount of blood loss during surgery,
and the number of dissected lymph nodes around the recurrent laryngeal nerves (No. 106). In both groups,
no patients required conversion to open thoracotomy [Table 2]. There were no significant differences
in total morbidity rate, the incidence of respiratory complications or anastomotic leakage (≥ Grade 2).
Regarding RLN palsy, vocal cord motility was checked in all patients by endoscopy on postoperative day
1, and any dysmotility was defined as RLN palsy (≥ Grade 1). The incidence of RLN palsy decreased to
less than half (19.8% to 9.6%) after standardization (P = 0.061) [Table 2]. There were also no significant
differences in ICU stay and postoperative hospital stay, and there were no postoperative mortalities in
either group.

Change in thoracoscopic operative time
There was a significant difference in thoracoscopic operative time between the pre-standardization group
and the post-standardization group [n = 91, 232.0 (202.8-264.0) min vs. n = 83, 209.0 (176.0-235.0) min,
(P < 0.001)] [Table 2]. The moving average curve showed that the thoracoscopic operative time decreased
markedly during the phase of microanatomy-based standardization of UMLD (from 350 cases to 400 cases)
and stabilized [Figure 4].

DISCUSSION
When most MIEs were performed via TELP, there were reports that precise mediastinal lymph node
dissection by MIE was as feasible as that by open thoracotomy with the added advantages of lesser decrease
[4,5]
in respiratory function and lower respiratory complication rates . However, even now, it is important
in TELP to have a special team composed of three experts (i.e., surgeon, assistant, and endoscopist)
to perform the procedure smoothly. On the other hand, an excellent surgical field contributed simply
by gravity and artificial pneumothorax without the need for an assistant is one advantage of TEPP.
Furthermore, the improved ergonomics for the surgeon in TEPP is another advantage.

In the early phase of introducing TEPP in this decade, there were some reports about its conferred
advantages for lymph node dissection, especially in the upper mediastinum [9-12] . Along with the recent,
remarkable progress of endoscopic optical instruments such as 3D and 4K ultra-HD, there have also been
reports about the microanatomy-based surgical concept for MIE, similar to total meso-rectal excision in
rectal cancer surgery [13-18] . More recently, we have established the microanatomy-based standardization
using the concept of the meso-esophagus wrapped with the visceral and vascular sheaths and reported