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Editorial |
Division of Surgical Oncology, University of Vermont, 89 Beaumont Avenue, E309C Given Building, Burlington, Vermont 05405
Correspondence: Address correspondence and reprint requests to: Seth P. Harlow, MD; E-mail: seth.harlow{at}uvm.edu.
Sentinel node biopsy techniques have gained rapid acceptance in the medical community as being an accurate tool for the pathologic staging of regional lymph nodes in patients with clinically node-negative breast cancer. Two large multicenter clinical trials, the National Surgical Adjuvant Breast and Bowel Project B32 and the American College of Surgeons Oncology Group Z10 trials, have recently completed accrual and should give us definitive proof that these minimally invasive procedures provide regional disease control and patient survival equivalent to those with standard axillary node dissection, with less morbidity. A great deal of attention is now being paid to determining the most e8ective methods for performing these procedures and what factors may influence their success. In this issue of Annals of Surgical Oncology, Rousseau et al.1 describe the factors that may influence the ability to visualize sentinel nodes on preoperative lymphoscintigraphy and the effect that nonvisualization has on the outcome of the sentinel node procedure.
Lymphoscintigraphy has been used routinely in sentinel node procedures for melanoma and has been quite useful in this role because of the variability in lymphatic drainage patterns seen in this disease. However, lymphoscintigraphy has been met with mixed enthusiasm for sentinel node identification in breast cancer. From the surgeon’s perspective, for lymphoscintigraphy to be a clinically useful tool, it should have a high rate of success in identifying the location of the sentinel node, and there should be some ambiguity as to which nodal basin the sentinel node will be located in before the scan is performed. The track record for lymphoscintigraphy in breast cancer has been for only moderate success in identifying the sentinel node site (only 78.5% successful in this study), whereas the presence of unsuspected nodal drainage sites is relatively uncommon, especially if one considers the internal mammary basin as a known potential drainage site. In this study,1 the authors made sure to use a technique that would be expected to give a high level of success for visualizing sentinel nodes. All injections were given in the periareolar region, were of small volume (.1 mL), and were of adequate dose (30–40 MBq). Common problems identified in the past that have inhibited the success of lymphoscintigraphy in breast cancer have been the overlap of injection site activity with nodal drainage sites and a lack of sufficient tracer reaching the sentinel nodes. Each of these should have been avoided by the technique used. The 21.5% nonvisualization rate in this study is in fact better than rates in many reports in the literature,2–3 but from the standpoint of the surgeon, this rate is still relatively high. This is further borne out by the fact that in 84.6% of patients in whom there was nonvisualization of a sentinel node by scan, a sentinel node was found by the surgeon using the gamma detector at the time of operation. Additional sentinel nodes were also found when blue dye was included, and this increased the sentinel node identification rate to 88.4%. As would be expected, if a sentinel node was identified on preoperative lymphoscintigraphy, the sentinel node identification rate was higher (93.2%), but it was still not 100%. The only factor found to be significantly correlated with nonvisualization of sentinel nodes was patient age: identification rates decreased with increasing age. There was a trend for the patients with nonvisualized nodes to have a higher incidence of macrometastases in their sentinel nodes, but there was a higher incidence of micrometastases in the patients with visualized sentinel nodes. There was no evidence that any extra-axillary sentinel node drainage was identified in patients on this study—a finding compatible with the previous reports that used periareolar injections.4
On the basis of results from this study and others, it is difficult to conclude that there is enough of a benefit from lymphoscintigraphy in breast cancer to make it a routine part of the standard sentinel node procedure. For the surgeon who is properly trained to evaluate all possible nodal drainage sites with the gamma detector during surgery, the success rate for identifying sentinel nodes routinely exceeds 90%.5 When probe evaluations are combined with the use of blue dye tracers, this success rate is even higher. The surgeon is also quite capable of evaluating extra-axillary nodal locations with the probe to determine whether these represent an important drainage site for an individual patient. An example of this was the defined method of sentinel node surveying used by surgeons in the National Surgical Adjuvant Breast and Bowel Project B32 trial. In this trial, surgeons were provided with detailed instructions and training on how to perform a comprehensive survey of the potential sentinel node drainage sites without the requirement of preoperative lymphoscintigraphy. In this trial, the success rate for identifying sentinel nodes by the surgeon was 97%,6 and the vast majority of patients did not have lymphoscintigraphy. This is not the only study to demonstrate that successful sentinel node localization in breast cancer can be performed effectively without preoperative lymphoscintigraphy, because this was also the conclusion of a study by McMasters et al.7 in 2000.
This is not to say that lymphoscintigraphy in breast cancer does not have applications. Certainly for surgeons who are new to the technique, having a road map to assist them can be quite helpful and may improve their success rates in localizing nodes. Additional indications may include patients at higher risk for sentinel node localization failure, such as elderly patients, obese patients, or patients with extensive previous operation of the breast or axilla. If a scan is performed, however, the surgeon should not abandon the search for sentinel nodes simply because a node is not visualized. As was demonstrated in this study, a significant number of these nodes will be found by the surgeon by using the much more sensitive handheld gamma probe, blue dye, or both. As was also pointed out in this study,1 there is a significant risk that these patients will indeed have clinically relevant metastatic disease, and if a sentinel node is not found, the patient should have a standard axillary lymph node dissection. In the typical breast cancer patient, however, the routine use of preoperative lymphoscintigraphy is a test that has been shown to be of minimal benefit to the surgeon. It simply increases medical costs, may cause unnecessary delays in the surgical procedure, and, therefore, should not be considered an essential part of the sentinel node process.
Received for publication March 10, 2005. Accepted for publication April 17, 2005.
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