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Page 2 of 9 Takeuchi et al. J Cancer Metastasis Treat 2018;4:38 I http://dx.doi.org/10.20517/2394-4722.2017.83

(ESD) is accepted as a less invasive procedure without gastrectomy for the resection of cT1 gastric cancer .
[1]
Laparoscopic gastrectomy is considered as an indispensable option between ESD and distal or total gastrectomy
with open laparotomy for early-stage gastric cancer . Laparoscopic distal gastrectomy (LDG) is comparable
[2]
with open distal gastrectomy for early gastric cancer, and can be performed in clinical practice . Many
[3,4]
patients with gastric cancer currently undergo LDG and laparoscopic total gastrectomy (LTG) with standard
lymphadenectomy . LDG and LTG contribute to better aesthetics and earlier postoperative recovery after
[1-4]
surgery . However, the extent of gastrectomy and remnant gastric function may affect patients’ quality of life
[5]
(QOL) after surgery, resulting in several complications such as dumping syndrome and loss of body weight due
to the disturbance of oral food intake. Therefore, function-preserving gastrectomy in addition to laparoscopic
surgery could be considered in patients with early-stage gastric cancer indicated for these procedures.

Function-preserving minimized gastrectomy procedures, including partial and segmental gastrectomy,
with modified lymphadenectomy are thought to improve postoperative gastric function compared to the
standard gastrectomy. However, certain incidences of nodal skip metastasis in the second compartment or
unpredicted station remain to be solved in these procedures. The sentinel node (SN) mapping and biopsy
could overcome these issues as a novel intraoperative examination for accurate diagnosis of nodal metastasis
in early-stage gastric cancer.

The SN is considered as the first lymph node(s) receiving lymphatic drainage from the primary tumor site ,
[6,7]
and are regarded to be the first possible node(s) of metastasis from the primary lesion. Theoretically if SNs
are pathologically negative for cancer metastasis, unnecessary extended lymphadenectomy can be avoided.
SN navigation surgery is defined as a less invasive surgical procedure with modified lymphadenectomy by
the diagnosis of SN metastasis. SN navigation surgery can prevent unnecessary lymphadenectomy and the
occurrence of associated postoperative complications, and result in improving the patients’ QOL.

SN mapping and biopsy were firstly utilized in breast cancer and melanoma, and subsequently attempted to
other solid tumors . Several studies involving SN mapping and biopsy for early-stage gastric cancer showed
[7-9]
favorable SN detection rates and accuracy to predict nodal metastatic status [10,11] . Based on the studies, we
have been developing a novel approach which combines laparoscopic function-preserving gastrectomy with
SN mapping.

LAPAROSCOPIC SN MAPPING AND BIOPSY PROCEDURES FOR GASTRIC CANCER
Combination of radioactive colloids with blue or green dyes as a dual tracer method is currently thought to
be the standard procedure for successful SN mapping in early-stage gastric cancer [10,11] . The accumulation
of radioactive colloids in SN enables the detection of SN using hand-held gamma probes. In addition, blue
dye is useful for real-time visualization of lymphatic flow even in laparoscopic surgery. Technetium tin
99m
colloids and technetium sulfur colloids are mainly utilized as radioactive tracers, and indocyanine green
99m
(ICG) is commonly used for dye tracer.

In our institutions, the indication to SN mapping and biopsy is currently limited to the patients with clinical
T1 tumors over the ESD criteria, primary tumors of < 4 cm in tumor diameter, with clinical N0 gastric
cancer [10,11] . In our institution, 2.0 mL (150 MBq) of technetium tin colloid is injected endoscopically a
99m
day before surgery into the submucosal layer surrounding the primary lesion. Injection of the tracer into the
submucosal layer using an endoscopic puncture needle facilitates more accurate tracer administration than
laparoscopic injections from the seromuscular site of the gastric wall. Technetium tin colloid which has
99m
relatively large particle size (approximately 200 nm in diameter) accumulates in the SNs after the endoscopic
injection into the primary tumor site.