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Joyce Eisenberg Keefer Breast Center and Division of Surgical Oncology, John Wayne Cancer Institute, Saint John's Health Center, Santa Monica; Statistical Coordinating Unit, John Wayne Cancer Institute, and Department of Nuclear Medicine, Saint John's Health Center, Santa Monica, California
| ABSTRACT |
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Key Words: breast cancer lymphoscintigraphy sentinel node
| INTRODUCTION |
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probe to identify the sentinel node (512). Although the techniques used for preoperative lymphoscintigraphy are highly variable, successful identification of sentinel nodes is between 75% and 98% (712). Geometric and other factors affecting kinetics of radiopharmaceutical migration and success of sentinel node identification have not been extensively studied, particularly the effect of patient position when imaging is undertaken after recent biopsy. Therefore, we evaluated the effect of a change in patient position to obtain a modified oblique view of the axilla (MOVA) and compared this with a standard anterior view of the supine patient for identification of AX sentinel nodes. Second, we examined the effects of age, weight, breast size, method of biopsy, and interval from biopsy to lymphoscintigraphy on the rate of sentinel node identification and the transit time of the radiopharmaceutical. Patterns of lymphatic drainage were correlated with tumor location.
| MATERIALS AND METHODS |
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Lymphoscintigraphy
Preoperative breast lymphoscintigraphy was performed after preparing the skin with alcohol and using 2 mL 1% xylocaine for local anesthesia. A total of 1216 MBq 99mTc-sulfur colloid (CisUS, Bedford, MA), passed through a 200-nm Millipore filter (Millipore Corp., Bedford, MA) in a total volume of 38 mL, was injected around the tumor or in the wall of the biopsy cavity. The volume injected varied with the size of the breast. Injections were not performed into biopsy cavities or seromas.
Planar images of the breast, axilla, supraclavicular, and infraclavicular regions were acquired using a scintillation camera with acquisition times that allowed adequate visualization of the lymphatic drainage basin. Usual acquisition times varied from 1 to 5 min. MOVA images were obtained after elevating the ipsilateral shoulder to 45° on a triangular foam wedge and raising the arm overhead. Imaging began immediately after injection and continued sequentially until sentinel nodes were identified. After the AX sentinel nodes were identified, a handheld
probe was used to confirm the location of the nodes. The skin was marked on the basis of confirmation of image localization by the handheld
probe. If sentinel nodes were not identified by 46 h, the patient was brought back for imaging the next day. Transit times from injection to sentinel node identification were recorded. AX, IM, and CL basins were monitored in all patients to determine primary and secondary drainage. Once the AX sentinel nodes were localized and marked on the skin, the patient was moved to the supine position and imaged in the anterior projection using the same acquisition times. Anterior supine and MOVA images were compared for success in identification of sentinel nodes.
SLND
All patients underwent AX SLND either the same day or 1 d after breast lymphoscintigraphy. No patient underwent IM or CL SLND. SLND was performed using vital dye or a handheld
probe (or both). The specific technique was chosen at the discretion of the attending surgeon. For the studies performed with vital dye, 35 mL isosulfan blue (Lymphazurin 1%, U.S. Surgical Corp., Norwalk, CT) were injected into the breast parenchyma adjacent to the primary tumor or into the wall of the biopsy cavity if a previous excision had been made. Through a separate axillary incision, a blue lymphatic was dissected and traced to blue sentinel nodes, which were excised. After SLND, the primary tumor was removed during total mastectomy or lumpectomy. A complete axillary lymph node dissection was performed only in patients whose sentinel nodes were positive for metastases.
For the studies performed using radioguided surgery with a
probe, an incision was placed over the hot spot in the axilla, and, using the probe as a guide, radioactive sentinel nodes were removed until counting rates dropped to background level. Some studies were performed using a combination of the 2 techniques. Because not all dissections were performed using both techniques, we did not correlate blue sentinel nodes with radioactive sentinel nodes.
Sentinel nodes were bivalved and submitted for frozen or permanent section. Frozen tissue was processed routinely for permanent section using hematoxylin and eosin staining. Sentinel nodes were submitted in separate cassettes for paraffin embedding. If metastases were not identified using hematoxylin and eosin, immunohistochemistry was performed using anticytokeratin antibodies (MAK-6; Ciba-Corning, Alameda, CA). Six to 8 sections were examined from each sentinel node.
Data Analysis
The 2 primary outcome measures were AX sentinel node identification rate by lymphoscintigraphy using the 2 imaging views and transit time of the radiopharmaceutical to the sentinel node after injection. The secondary outcome measures were the location of the sentinel nodes in the AX, IM, or CL drainage basins. The 2 primary outcome measures were assessed with respect to 6 factors: age, weight, breast size, injection quadrant, interval from biopsy to lymphoscintigraphy, and method of biopsy. Breast size was determined subjectively by the same 2 technologists for each case and was designated as small, medium, or large.
Statistical Analysis
The outcomes for comparing sentinel node identification from the 2 images were classified as MOVA equivalent to the anterior view, MOVA superior to the anterior view, or seen only with MOVA. Logistic regression was used to assess the effect of each of the 6 factors on sentinel node identification using MOVA and the anterior view. A nonparametric permutation test on the linear model was performed to determine the effect of the 6 factors on radiopharmaceutical transit time. A normality test showed that transit time was not distributed normally. Fisher's exact test was used to analyze the association between injection quadrant and sentinel node location. All Ps were 2-tailed, and an
level of 0.05 was considered significant.
| RESULTS |
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| DISCUSSION |
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All but 1 patient had lymphoscintigraphy showing some AX drainage. Only 7 of 76 studies revealed dominant IM drainage. These migration patterns are consistent with other reports of lymphoscintigraphy before SLND (Table 5). Migration to non-AX sites was not predictable by the quadrant of the breast injected. Other studies have shown that IM drainage can occur with both inner and outer quadrant lesions (7,12). IM drainage is usually accompanied by AX drainage. The 1 patient with exclusive IM drainage on lymphoscintigraphy had a blue-stained AX sentinel node visualized during SLND. In many cases, the 2 methods for identifying the sentinel node are complementary, and the dye or radiopharmaceutical will aid in sentinel node detection when the other method fails (811).
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probe (1315). After injection of the radiopharmaceutical, the patient is taken to the operating room; then, usually with the patient under general anesthesia, hot spots are marked on the skin using the
probe. The time spent searching for hot spots with the probe is likely equal to that of lymphoscintigraphy. However, lymphoscintigraphy also documents drainage to all lymph node areas and more easily identifies failed radiopharmaceutical migration. If hot spots are not identified with the probe, then reasons other than migration failure, such as probe malfunction, may be responsible for failed sentinel node detection; this can be difficult to appreciate without a preoperative lymphoscintigram. Similarly, a hot spot found with the
probe may originate from radiopharmaceutical that has leaked onto the skin; this would be obvious on lymphoscintigraphy but more difficult to deduce with a probe. This may be 1 reason why sentinel nodes were not always detected beneath the skin hot spots in the multicenter trial reported by Krag et al. (13). In the same trial, all false-negative findings occurred with primary lesions that were in close proximity to the axilla. Lymphoscintigraphy using MOVA can aid in identifying nodes that are close to the injection site, a difficult distinction when the probe alone is usedparticularly if the patient is kept supine during probe localization, as in the multicenter trial. Finally, it is uncommon for the
probe alone to identify a radioactive sentinel node that was not localized by lymphoscintigraphy (6,9). When multiple nodes are hot, the probe alone cannot reliably distinguish sentinel from nonsentinel nodes, whereas dynamic lymphoscintigraphy easily permits this distinction. Therefore, preoperative lymphoscintigraphy will usually reveal the sentinel node before radioguided surgery, making it unnecessary to remap drainage sites intraoperatively with the
probe. SLND can proceed quickly with the incision over the skin marking. Different techniques have been proposed for each step in breast lymphoscintigraphy. Some investigators claim that a radiocolloid containing small particles, such as 99mTc-antimony sulfide colloid (99mTc-ASC; 312 nm), allows better migration of tracer and improved detection of sentinel nodes (12), whereas others prefer the larger particles of 99mTc-colloidal albumin (2001000 nm) because fewer nonsentinel nodes are labeled (9). Often, the agent chosen is the only agent available to the investigator. Currently, no radiopharmaceuticals have been approved for lymphoscintigraphy in the United States. 99mTc-sulfur chloride is approved for intravenous injection and reticuloendothelial imaging but is also widely used for lymphoscintigraphy, both with and without prefiltration (16). 99mTc-human serum albumin, in noncolloidal form, is also approved in the United States for blood-pool imaging, and it has also been widely used as a lymphoscintigraphic agent, although, currently, it is not commercially available. We use sulfur colloid that has been passed through a 0.2-µm filter to select smaller particles; our results compare favorably with those of investigators using other agents (7,9,10,12).
Although we use a peritumoral injection, others such as Veronesi et al. (5) advocate a subdermal injection. In a study comparing subdermal and peritumoral injection techniques, the former reached the sentinel nodes more quickly but no difference was found in the overall sentinel node identification rate (9). Interestingly, most patients received subdermal injections, and overall IM drainage was 2% in this study, much lower than the 11%39% reported in other series (Table 5). An interesting comparison can be made from a study of cutaneous lymphoscintigraphy patterns obtained for melanoma of the breast skin and anterior trunk on 62 patients using 99mTc-ASC: No IM drainage was recorded (17). Furthermore, Alazraki et al. (18) found that subdermal injections failed to identify IM sentinel nodes that had been revealed by peritumoral injections in the same patients. Therefore, although most breast cancers drain to the axilla, peritumoral injections seem to show somewhat different drainage patterns than subdermal injections.
Injection volume is another variable that is not standardized. Successful sentinel node localization has been achieved using volumes as low as 0.4 mL and as high as 8 mL. Some authors are opposed to larger volumes, believing that such nonphysiologic perturbation may cause erroneous labeling of a lymph node as the sentinel node (17). However, there is no evidence that large injectates will enter lymphatics leading to nonsentinel nodes; rather, greater volumes of injection increase interstitial pressure, which increases lymphatic flow (19). The theoretic merits of a small-volume injection, though conceptually more elegant, have not been proven. Success rates using larger volumes of 99mTc-sulfur chloride are high, the technique is safe, and validation studies with complete axillary dissection have yielded few false-negative sentinel nodes.
| CONCLUSION |
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probe and vital dye for identification of all sentinel nodes in patients with breast cancer.
| ACKNOWLEDGMENTS |
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| FOOTNOTES |
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For correspondence or reprints contact: Edwin C. Glass, MD, Nuclear Medicine Section-115, West Los Angeles VA Medical Center, 11301 Wilshire Blvd., Los Angeles, CA 90073.
| REFERENCES |
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