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Blog aimed at residents in surgery
 URL :  www.surgical-oncology.net             e mail surgoncnet@gmail.com
The Sentinel Lymph Node in Gastric Cancer: second updating.

Romeo Giuli MD, resident.
School of General and Emergency Surgery.
University of Siena.   Italy.



May 2002.     Review Article.

To previous article about Sentinel Node in GC
To the first updating
To the third updating


Following a preliminary article published ( 2 ), Kitagawa et al.affirm that radio-guided SN mapping is an accurate diagnostic procedure for detecting lymph node metastasis in patients with early-stage gastric cancer.
Using radio-guided methods, SNs were detected in 138 (952 per cent) of 145 patients. The SN was positive in 22 of 24 patients with lymph node metastasis. The incidence of metastasis in the SNs (78 per cent) was significantly higher than that in the non-SNs (03 per cent) (P < 001). The diagnostic accuracy according to SN status was 986 per cent (136 of 138).

Clinical diagnosis was made by examination of endoscopic biopsy specimens, and the absence of apparent lymph node involvement by diagnostic imaging was confirmed by preoperative CT and conventional ultrasonography. The depth of tumour invasion was evaluated on the basis of endoscopic findings and double contrast gastrography. One hundred and forty-five patients requiring curative gastrectomy with D2 or modified D2 lymphadenectomy (removal of all N1 nodes and nodes along the left gastric artery and common hepatic artery) with a diagnosis of clinical T1 or T2, N0 M0 status were enrolled.
After the resection, the absence of residual radioactivity in the abdomen was confirmed intraoperatively with a hand-held probe (Navigator; AutoSuture Japan, Tokyo, Japan).
The radioactivity of all the resected nodes was measured individually with a hand-held counter (window setting above 95 keV, measuring time 20 s) and a well-type scintillation counter (ARC-300; Aloka, Tokyo, Japan) (window setting 126-154 keV, measuring time 60 s). SNs were defined as nodes containing ten times more radioactivity than surrounding tissue. The number of hot nodes was compared between groups with different timing of the tracer injection. Endoscopic submucosal injection (using technetium-99m-radiolabelled tin colloid ) was considered a reasonable and feasible route of administration of radioactive tracer for lymphatic mapping of gastric cancers.
A single haematoxylin and eosin-stained section of a formalin-fixed paraffin-embedded specimen of each lymph node harvested was examined by a pathologist who was blinded to the SN status. The pathological status of the SNs was compared with that of the remaining regional nodes (non-SNs). The successful identification rate of SNs, number, distribution and accuracy of SN assessment with respect to the positive or negative status of regional nodes were evaluated.

In gastrointestinal cancers, the lymphatic network may be more complex than that in breast cancer, and it may be difficult to visualize all the SNs distributed in unexpected areas by the vital blue dye method. In fact, the current data indicated a relatively high incidence (approximately one-third) of direct distribution of radioactive tracer in the second regional lymph node compartment in gastric cancer. This may be the major mechanism of so-called skip metastasis in gastric cancer. In these cases, SNs in the second compartment are considered functionally to be first compartment.

In the field of surgical treatment of gastric cancer, successful SN mapping has great potential to detect micrometastatic disease by focusing on SNs as selected targets for evaluation and for recognition of unusual lymph drainage.

Furthermore, this technique has great potential application for development of novel minimally invasive surgical techniques. Curative laparoscopic surgery for mucosal gastric cancer has been reported . Laparoscopic wedge resection with a safe surgical margin should be sufficient for curative treatment of early gastric cancer without lymph node metastasis. In fact, laparoscopic detection of SNs in gastric cancer using an abdominal probe (AutoSuture Japan, Tokyo, Japan) was feasible in a preliminary study. Several issues, such as the sensitivity of intraoperative pathological examination and the technique of laparoscopic SN detection, remain to be resolved before wide clinical application of this procedure. However, from this initial experience, it is reasonable to conclude that radio-guided SN detection has potential value in the staging and treatment of patients with early gastric cancer ( 1 ).

References

1) Y. Kitagawa, H. Fujii, M. Mukai, T. Kubota, Y. Otani and M. Kitajima. Radio-guided sentinel node detection for gastric cancer. British Journal of Surgery, Volume 89 Issue 5 Page 604 - May 2002.

2) Y Kitagawa et al. Laparoscopic detection of sentinel lymph nodes in gastrointestinal cancer: a novel and minimally invasive approach. Annals of Surgical Oncology 2001, 8 (9S): 86-89.

3) Y Kitagawa et al. The role of the sentinel lymph node in gastrointestinal cancer. Surgical Clinics of North America, 2000, volume 80, n 6, 1799-1809.

4) Bilchik AJ, Giuliano A, Essner R, Bostic P, Kelemen P, Foahag LJ et al. Universal application of intraoperative lymphatic mapping and sentinel lymphadenectomy in solid neoplasms. Cancer J Sci Am 1998; 4: 351-8.



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