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Li et al. Mini-invasive Surg 2019;3:15 I http://dx.doi.org/10.20517/2574-1225.2018.13 Page 3 of 6

have no difference as well. Overall survival after TAE was significantly longer than after THG (33.6 months
[13]
vs. not reached, P = 0.02) . It suggested TAE isn’t worse than THG for Siewert type II AEG, especially for
advanced patients who had neoadjuvant chemotherapy. But this study didn’t report the length of esophagus
invasion, which may influence the surgical approach chosen.

In terms of surgical extent of type II AEG, it is related to surgical approach. In order to evaluate the
worldwide trends in surgical techniques for esophageal cancer surgery, a worldwide survey was performed
among surgeons. In Asia gastrectomy was more popular, whereas in North America the majority procedure
[14]
was esophagectomy . And thoracic surgeons may prefer distal esophagectomy, while abdominal surgeons
prefer proximal or total gastrectomy via transhital approach. And a sufficient resection margin is another
[15]
prognostic factor for oncology safety. Mine et al. demonstrated that proximal margin length of more
than 20 mm in resected specimens seem satisfactory for patients with type II AEG by transhital approach.
Frozen section examination of the resection line is recommended by the Japanese gastric cancer treatment
[16]
guidelines to ensure an R0 resection .

On the basis of the best evidence so far, JCOG 9502, for Siewert type II AEG with esophagus invasion of 3
cm or less, transhiatal approach is safety and effective. It is necessary to conduct well-designed multicenter
clinical trials to investigate appropriate approach for type II AEG with a larger lesion.

OPTIMAL EXTENT OF LYMPH NODE DISSECTION FOR SIEWERT TYPE II AEG
Siewert type II AEG is located in the boundary of distal esophagus and gastric cardia, the pathway of
lymph metastasis is not same as esophagus or gastric cancer alone. In previous retrospective study,
mediastinal lymph node involvement rate was 46.2%-65.0% for type I, 12.0%-29.5% for type II, and 6.0%-9.3%
[19]
for type III tumors [17,18] . Nunobe et al. claimed that the more esophagus invaded, the higher lymph node
metastasis rate is.

The optimal extent of lymph node dissection for Siewert type II AEG remain uncertain. A nation-wide
[20]
retrospective study of lymphadenectomy for EGJ cancer was conducted in 2012 in Japan . 2807 patients
without preoperative therapy were included in the analysis. The frequency of dissection for mediastinal
lymph node was higher in esophagus-predominant cancer than stomach-predominant cancer. With
respect to esophagus-predominant cancer, the lymph node dissection rate is higher in lower mediastinal
lymph node than upper or middle mediastinal (40% vs. 15%). For stomach-predominant cancer, the
mediastinal lymph node dissection focuses mainly on lower mediastinal, and advanced cancer especially.
The possibolity of metastasis rose as the pT stage increased, and rates of metastasis is high in No. 1, 2, 3, 7.
Mediastinal lymph node metastasis could be found in esophagus-predominant cancer, especially in lower
mediastinal. On the contrast, it is rare in stomach-predominant. And rates of metastasis at No. 4sa, 4sb,
4d, 5 and 6 were very low, despite their high dissection rates especially in stomach-predominant cancer
cases. Therefore, lymph node metastasis is mainly in the abdominal and lower mediastinal for Siewert type
II AEG. Another study has similar result. It reviewed 381 Siewert type II AEG retrospectively. The nodal
metastasis mainly founded in No. 1, 2, 3, 7, 11p and lower mediastinal. The middle and upper mediastinal
[21]
metastasis rate is low, but related to extremely poor prognosis .

It still doesn’t have a standard lymph node dissection extent. The Japanese Gastric Cancer Association
published a temporary lymphadenectomy guideline for junctional cancer ≤ 4 cm. It is based on the tumor
[16]
location, histology and T-categories . Abdominal lymph node dissection can refer to gastric cancer, and
No 4, 5, 6 can be omitted in early stage cases, because of low metastasis rate. Lower mediastinal should
dissect routinely, but upper and middle mediastinal not. According to personal experience, lower thoracic
paraesophageal lymph nodes (No. 110) and supradiaphragmatic lymph nodes (No. 111) can be resected
via transhital approach, but it’s difficult to resect posterior mediastinal lymph nodes (No. 112) because of