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Page 6 of 9 Ishihara. Mini-invasive Surg 2021;5:36 https://dx.doi.org/10.20517/2574-1225.2021.72

Table 2. Curative ability assessment of endoscopic submucosal dissection based on cancer invasion depth and vascular invasion
status

Curative resection
√ Pathological T1a-epithelial/lamina propria without vascular invasion
Non-curative resection and undetermined recommendation for additional treatment
√ Pathological T1a MM without vascular invasion
Non-curative resection and additional treatment recommended
√ Pathological T1b cancer invading the submucosa
√ Pathological vascular invasion-positive

MM: Muscularis mucosae.

Cancer invasion depth and vascular invasion
(p)EP/LPM cancer
Although metastasis may develop in (p)EP/LPM cancers without vascular invasion, the risk of the
[35]
metastasis is as low as 0.4% . The resection is judged as curative if the histological findings of the resected
specimen show (p)EP/LPM cancer without vascular invasion and if the horizontal and vertical margins are
negative. Other cancers, (p)MM, (p)SM, or tumors with vascular invasion are considered as non-curable in
terms of cancer invasion depth and vascular invasion.

(p)MM cancer
The ESD/EMR Guidelines for Esophageal Cancer analyzed the incidences of metastasis of (p)MM cancers
[13]
in surgically and endoscopically resected patients. For (p)MM cancer without vascular invasion, the lymph
[36]
node metastasis rate was 4/38 (10.5%) in surgically resected patients , compared with 12/216 (5.6%) in the
follow-up observation group after endoscopic resection . Given the considerable risk of metastasis,
[13]
pathologically diagnosed (p)MM cancer without vascular invasion is judged as non-curable. However,
considering the reduced quality of life and the possibility of treatment-related death associated with
additional surgical resection, as well as delayed adverse events and treatment-related deaths following
additional chemoradiotherapy, these treatments are not conducted in most cases. In addition, patients are
usually informed that metastasis can occur at certain rates and that it is crucial to perform careful follow-up,
including screening for metastasis.

Regarding (p)MM cancer with vascular invasion, the lymph node metastasis rate was 5/12 (41.7%) in
[36]
surgically resected patients compared with 3/14 patients (21.4%) in the follow-up observation group after
endoscopic resection . Given the high risk of metastasis, pathologically diagnosed (p)MM cancer with
[13]
vascular invasion is thus considered to be non-curable, but additional treatment with surgical resection or
chemoradiotherapy is recommended for these patients.

(p)SM cancer
The ESD/EMR Guidelines for Esophageal Cancer analyzed the incidences of metastasis of (p)SM cancers in
surgically and endoscopically resected patients. Analyses of resected specimens from patients with
(p)SM1/SM2 esophageal SCC who received surgical resection as first-line treatment, including patients with
vascular invasion, showed concurrent lymph node metastasis in 43/170 patients (25.3%) with (p)SM1
cancers and 49/196 patients (25%) with (p)SM2 cancers, compared with 8/43 patients (18.6%) with (p)SM1
cancers and 3/20 patients (15%) with (p)SM2 cancers in the follow-up observation group of patients who
received endoscopic resection as first-line treatment, including patients with vascular invasion. In addition,
recent retrospective study showed that lymphatic invasion and (p)SM2 were independent risk factors for
metastatic recurrence . Given the high proportion of metastasis, a histological finding of (p)SM cancer is
[37]
judged as non-curable, and additional treatment with surgical resection or chemoradiotherapy is