Elsevier

Surgical Clinics of North America

Volume 80, Issue 6, 1 December 2000, Pages 1799-1809
Surgical Clinics of North America

THE ROLE OF THE SENTINEL LYMPH NODE IN GASTROINTESTINAL CANCER

https://doi.org/10.1016/S0039-6109(05)70262-0Get rights and content

The sentinel node concept has been validated in the fields of breast cancer and malignant melanoma.1, 6, 12, 14, 17 To date, application of the sentinel lymphadenectomy is considered to be one of the most important modalities for the multidisciplinary management of breast cancer and melanoma. The accuracy of prediction of nodal status by sentinel node navigation, in recent studies for breast cancer, is more than 95%.2, 16 The feasibility and diagnostic reliability of sentinel node mapping of gastrointestinal (GI) cancers, however, are still unclear and controversial. There are several reasons why the sentinel node concept has not been well studied in GI cancers. It has been thought that nodal metastases occur in a random process and that second and third compartments of regional lymph nodes are likely to be involved in metastatic disease without involvement of nodes closest to the primary lesion of GI cancers. Generally, GI surgeons are skeptical about the application of the sentinel node concept for GI cancers because of the high incidence of skip metastases.11 It should be emphasized that so called “skip metastasis” has been defined according to the anatomic classification of regional lymph nodes and that the lymphatic drainage route must be patient-specific or lesion-specific. Therefore the investigation of the validity of the sentinel node concept in patients with GI cancers is important to establish a method for accurate staging by detecting micrometastasis, and to determine the application of less invasive surgery with modified lymph node dissection or even without dissection.

There are a number of studies on the lymphatic drainage system of GI cancers using small tracer particles including dyes and activated charcoal.7 Nearly all these reports have focused on the extent of lymphatic flow from the primary lesion and demonstrated the possibility of involvement of nodes distant from the lesion. These studies provided the theoretical background of prophylactic, extended lymphadenectomy for GI cancers. Only a few studies, however, have investigated the lymphatic flow system of GI cancers from the point of view of the sentinel node concept, which should not be confused with interpretation of previous studies on GI lymphology.

Section snippets

INDICATION OF SENTINEL NODE NAVIGATION IN GI CANCERS

Although there are several indications for sentinel node navigation for breast cancer, including tumor size, location, previous treatment, and nodal status evaluated by diagnostic imaging, there is no definitive conclusion. As for GI cancers, the authors would like to recommend almost the same concept of indications with other diseases. Clinically, no regional node metastases (N0) cases with the tumor invasion limited to within the muscularis propria or submucosal layer would be a preferred

ADMINISTRATION OF THE TRACER PARTICLE

In the history of the investigation of lymphatic drainage routes in GI cancers, small particles such as dye and carbon particles have been used. Although these tracers are suitable to evaluate the extent of the lymphatic drainage route, it is not easy to identify the sentinel nodes because of rapid diffusion of these small particles. In the blue dye technique, the timing of injection of blue dye needs to be carefully monitored, as there is a short window of time during which selective

LYMPHOSCINTIGRAPHY

A combination of preoperative lymphatic mapping by lymphoscintigraphy and intraoperative probe detection is being used increasingly to identify sentinel nodes in melanoma and breast cancer. As for the GI cancers, preoperative lymphoscintigraphy also is useful for noting the distribution and the number of sentinel nodes. Particularly in the case of esophageal cancer, lymphatic drainage routes are complicated and variable among the patients. “Hot” spots often are observed in unexpected areas

INTRAOPERATIVE DETECTION OF THE SENTINEL NODES

A hand-held gamma probe (Navigator, AutoSure, Japan) was used to locate radioactive sentinel nodes (Fig. 4). Although the hand-held gamma probe is useful to identify sentinel nodes, it is important to avoid interference from high background radioactivity from the injection site. For this reason, collimation of the hand-held gamma probe is critical for localizing sentinel nodes, particularly in the laparoscopic approach. A combination of intraoperative endoscopic injection of blue dye and gamma

HISTOPATHOLOGIC EXAMINATION

To exclude bias in the preliminary study, a single hematoxylin and eosin–stained section of formalin-fixed, paraffin-embedded specimen of each lymph node was examined by pathologists who were not informed of the data for the incorporation of radioactive tracer. The pathologic status of the sentinel nodes was compared with that of the remaining regional nodes. The detectable rate of sentinel nodes, their number and distribution, and accuracy of the sentinel nodes with respect to positive or

FEASIBILITY AND VALIDITY OF SENTINEL NODE NAVIGATION IN GI CANCERS

Results and diagnostic significance of SN mapping in 85 cases of GI cancers (16 cases of esophageal cancer, 36 cases of gastric cancer, 33 cases of colorectal cancer) in the authors' first series are summarized in Table 1. In the pilot study, the detectable rate of sentinel nodes in patients with GI cancers, using 99mTc Sn colloid was almost satisfactory, considering the learning curve. In cases in which sentinel nodes were undetectable, several reasons were speculated, including tumor size,

SENTINEL NODAL STATUS FOR ACCURATE STAGING

As with other malignant diseases, the detection of sentinel nodes in GI cancers provides more accurate staging by focusing on specific lymph nodes in the resected specimen that are most likely to contain tumor metastases. Intensive analysis of the sentinel nodes, including serial sectioning, immunohistochemistry, and RT-PCR, would provide significant information with minimum effort. Sentinel node status is one of the most important clinical factors of information in decision making for the

APPLICATION FOR MINIMALLY INVASIVE SURGERY

Another important clinical factor in the application of the sentinel node navigation in GI cancer is to assess the extent of lymphadenectomy in each patient. Gastrectomy with systemic lymph node dissection (D1 or D2) has been considered a standard procedure for the treatment of early gastric cancer with potential for micro-lymph node metastases. The frequency of lymph node involvement, however, is less than 15% in early gastric cancer, in which the depth of invasion is limited within the

SUMMARY

Evaluation of the clinical significance of the sentinel node concept in GI cancer has just begun. The authors' preliminary data, using intraoperative radio-guided sentinel node navigation by preoperative endoscopic submucosal injection technique, followed by intraoperative gamma probing, suggested that it is worthwhile to continue evaluating this procedure to determine its role in an accurate staging, and a minimally invasive approach to early GI cancers.

ACKNOWLEDGMENTS

The authors would like to thank Dr. K. Nakamura for technical assistance in the analysis in nuclear medicine, and Dr. K. Nakazato and Dr. H. Kikuchi for their advice on radiation safety issues.

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Address reprint requests to Yuko Kitagawa, MD, Department of Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan, e-mail: [email protected]

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Copyright © 2000 W. B. Saunders Company. Published by Elsevier Inc. All rights reserved.