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Beth Israel Deaconess Medical Center Harvard Medical School Boston, MA 02215
Tuthill et al. [1] state that "the high success rate of lymphoscintigraphy in our study and its role in successful sentinel node biopsy support a role for routine lymphoscintigraphy before sentinel node biopsy in patients with breast cancer." This article shows that positive findings on a lymphoscintigram are highly correlated with successful identification of sentinel lymph nodes at surgery. However, the authors do not address the value of scintigraphic mapping apart from localization with the gamma probe and cannot justify the conclusion that "lymphoscintigraphy improved the success rate of sentinel node biopsy" [1].
This distinction is important because the specific role of scintigraphy (imaging) in this procedure is controversial, whereas nuclear medicine techniques using a gamma probe have been shown by many authors to improve the accuracy of sentinel node biopsy in breast cancer. Lymphoscintigraphic mapping is of proven usefulness in melanoma because of the variability of lymphatic drainage, particularly when the primary lesion is located on the trunk and when multiple nodal sites, and the pathways leading to them, need to be surveyed. The sites of drainage are more limited in the breast and presumably the gamma probe is more sensitive in identifying these sites. Lymph drainage in the breast is usually toward the axilla. The visualization of parasternal and supraclavicular nodes might influence subsequent radiation decisions, but these nodes are rarely biopsied and should be identified by surgeons experienced in using the gamma probe. Indeed, lymphoscintigraphy of the breast may be most useful as a guide for surgeons with limited experience in the use of these probes.
Injection of the breast with 99mTc sulfur colloid or another radiocolloid is performed preoperatively because these agents require more time to reach lymph nodes than do the intraoperatively injected aqueous solutions of dye. Injection is usually done in the nuclear medicine department for convenience and safety, and because this is the location of the scintigraphic equipment. For nonpalpable lesions, this injection is carried out after a localization procedure in the breast imaging area. Tuthill et al. [1] obtained scans immediately and at 15 and 30 min after injection and repeated the scanning process at 1 hr if the initial scans were nondiagnostic. If scintigraphic mapping were omitted, the radiocolloid injection might be more expeditiously and accurately accomplished at the time of the localization procedure. The need to perform two preoperative percutaneous imaging procedures in different locations adds to costs and the possibility of disruptive delays in surgery. On the other hand, most studies indicate the exact site of injection is inconsequential, and it may be more economical to bring the patient to the nuclear medicine department than to bring a member of that department to the breast imaging area.
Tutill et al. [1] found preoperative lymphoscintigraphic mapping was successful in identifying the sentinel node in 106 (88%) of 120 attempted procedures, and 105 of these 106 patients underwent successful biopsy. However, the association of positive findings on lymphoscintigraphy with successful sentinel node biopsy does not indicate this procedure contributed to that success. Regardless of the scintigraphic finding, the 105 successful sentinel node procedures had to have these nodes intraoperatively identified by either the gamma probe or the visual presence of blue dye. Indeed, 10 of the 14 patients who did not have a sentinel node identified at lymphoscintigraphy still had sentinel nodes identified and removed at the time of surgery; seven of these 10 were identified by the gamma probe.
In summary, the value of lymphoscintigraphy in breast surgery remains uncertain.
References
Indiana University Hospital Indianapolis, IN 46202
My colleagues and I thank Dr. Hall for his interest in our work. The role of routine preoperative lymphoscintigraphy in sentinel lymph node biopsy is controversial. We agree that the high association between successful lymphoscintigraphy and sentinel lymph node identification at surgery that we report [1] does not conclusively prove that the former contributed to the latter. Even though nonaxillary sentinel lymph nodes are rare in breast cancer, at our institution they are excised whenever encountered. In this regard, we find lymphoscintigraphy to be helpful. A recently reported survey [2] of 1000 fellows of the American College of Surgeons found that 60% of respondents routinely performed preoperative lymphoscintigraphy. Of these, 28% excised sentinel internal mammary lymph nodes whenever found. On this basis, we respectfully disagree with Dr. Hall's assertion that nonaxillary lymph nodes are "rarely biopsied" and that lymphoscintigraphy may be most helpful to inexperienced surgeons.
Sentinel lymph node biopsy in breast cancer is a relatively new and evolving procedure. The technical aspects of the procedure vary greatly from institution to institution. We hope that further research will help to define the optimum method for this exciting new technique.
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