Sentinel Node Biopsy and Axillary Dissection



Sentinel Node Biopsy and Axillary Dissection


Hiram S. Cody, III



In the pregenomic era, axillary lymph node status was the most important prognostic factor for patients with operable breast cancer and consequently the goals of axillary surgery have been (1) staging/prognostication, (2) local control, and (3) arguably, a small survival benefit. For these purposes, axillary lymph node dissection (ALND) has been the gold standard for most of the 20th century, but since the mid-1990s has largely given way to sentinel lymph node biopsy (SLNB). Here we will review the historic background of ALND and SLNB, the indications for each procedure, and the operative techniques.




Case Selection for SLNB

Early in the SLN era there were many putative contraindications to the procedure and much concern about the “learning curve” during which one’s early experience with SLNB should be validated by a planned “backup” ALND. It is now clear that SLNB is suitable for virtually all patients with cN0 operable invasive breast cancers and that—using standardized techniques—the “learning curve” is as short as one case (21). SLNB is also indicated for patients with ductal carcinoma in situ (DCIS) who require mastectomy (or for whom invasion is suspected based on the presence of a mass) and for patients with clinically suspicious nodes but a nondiagnostic needle biopsy. SLNB is indicated for patients who are cN0 but node positive on FNA or core biopsy, 50% of whom in our own experience (22) had 1 to 2 positive SLNs, meeting Z0011 criteria and avoiding ALND. SLNB is indicated for patients who are cN0 following neoadjuvant chemotherapy, whether they were node negative (23) or node positive, upfront (24). SLNB is reasonable but admittedly very low yield for prophylactic mastectomy, where invasive cancer will be found in a few percent of patients. SLNB is feasible in patients with locally recurrent breast cancer and prior axillary surgery (25), especially if fewer than 10 nodes were removed in a prior SLNB or ALND, but the benefit of “reoperative SLNB” is unproved (26). Finally, prior aesthetic breast surgery, augmentation or reduction, is not a contraindication to SLNB (27,28).


Technique of SLNB

SLNB requires close collaboration among the disciplines of nuclear medicine, surgery, and pathology and although SLNB works well with a variety of techniques, each institution will want to develop its own specialty-specific consensus protocols. The following represents the SLNB literature as a whole and our own institutional experience with more than 25,000 procedures since 1995.


Nuclear Medicine

The success of SLNB is maximized, and the false-negative rate is minimized, by the combination of radioisotope and blue dye, but radioisotope accounts for the greatest proportion of this success, and with experience the marginal benefit of blue dye diminishes (29,30). The isotope of choice is technetium (Tc99m) bound to a variety of carriers, most commonly sulfur colloid (United States), colloidal albumin (Europe), and antimony (Australia). Novel carriers and nonradioactive techniques (fluorescence, ultrasound microbubbles, and magnetic particles) (31) report mapping success comparable to legacy agents.

There is no standardization of isotope dose, particle size, volume of injectate, timing of injection, or site of injection, and many methods appear to work well. Our preference (32) is to inject 0.1 mCi (3.7 MBq) of unfiltered Tc99m–sulfur colloid on the morning of surgery or 0.5 mCi (18.5 MBq) the day before. With this protocol, which allows for radioactive decay (the half-life of Tc99m is 6 hours) we have observed equivalent results with same-day or day-before isotope (33). It appears that the performance of unfiltered and filtered isotope preparations is similar.

We inject a volume of 0.05 cc; this has the advantage of leaving a very small “hot spot” on the breast, so as not to overshadow the axilla in patients with upper outer quadrant tumors. We inject intradermally at a single site over the tumor, having found this technique superior to parenchymal or peritumoral injection. These results have been independently confirmed in a randomized trial by Povoski et al. (34) and in the large multicenter Louisville Sentinel Node Trial (35): superficial injections (intradermal, subdermal, or subareolar) were more successful than parenchymal (peritumoral) injection or dye-only techniques. Across the SLNB literature the false-negative rate of all methods was similar, suggesting that the lymphatics of the entire breast usually drain to the same few SLNs (36).

Although preoperative lymphoscintigraphy (LSG) is essential in SLNB for melanoma, its role in breast cancer is debatable. LSG does not improve the identification of axillary SLN, other than to alert the surgeon that more than one axillary SLN is present. Even when the LSG is negative, a hand-held gamma probe will usually identify “hot” SLN at surgery. LSG can identify nonaxillary lymphatic drainage (primarily to the internal mammary nodes) in a minority of patients, but the impact of this
information on treatment, local control, or survival is unproved.


Surgery

For breast conservation we perform SLNB under local anesthetic with intravenous (IV) sedation and for mastectomy under general anesthesia. Before starting surgery, we inject 1 to 5 cc of isosulfan blue dye subdermally in the breast, (a) at a single site over the tumor, (b) just superolateral to a surgical biopsy site, or (c) in the subareolar area. Using a hand-held gamma probe, we identify and mark the isotope injection site in the breast, any focal hot spots in the axilla, and any intervening hot spots that might suggest the presence of intramammary SLN.

SLNB is best done prior to the breast operation—while the lymphatics are still intact—and through a separate transverse skin line incision in the axilla. Even tumors high in the axillary tail will be further from the axilla than they appear, and one should avoid the temptation to do the entire operation through a single incision except perhaps for mastectomy done through a single oblique incision, where SLNB is easily done through the axillary end of the incision prior to proceeding with the mastectomy.

SLNB is best done under direct vision and with adequate exposure, as inadvertent division of sensory nerves probably accounts for most of the reported morbidity of SLNB. As dissection is deepened through the axillary fascia, any blue lymphatics are left intact and traced proximally into the axilla, blue nodes are identified, and the gamma probe is used to identify any “hot” nodes. SLN are usually found low in level I, but in about 25% of cases they are found at other locations: posteriorly along the latissimus muscle, higher in the axilla near the axillary vein, beneath the pectoralis minor in levels II to III, and (much less often) as Rotter (interpectoral) or intramammary SLN. The gamma probe is very useful throughout this dissection and is indispensable in the very large or fatty axilla where identification of blue lymphatics/nodes can be challenging.

All blue and/or “hot” nodes are removed, typically a median of 2 to 3 per patient. When multiple hot SLNs (or a diffusely hot axilla) are found, we make every effort to remove the hottest SLN, which will be positive in 80% of SLN-positive patients (37). We do not in general submit large numbers of SLN, having found that 98% of positive SLN are identified within the first three SLNs and 99% within the first four SLNs submitted (38). Another useful guideline is the “10% rule,” in which all nodes with counts ≥10% of the hottest node are submitted as SLN. For patients who were node positive prior to neoadjuvant chemotherapy, the false-negative rate of SLNB is minimized by using dual tracers (blue dye plus isotope) and by removing at least three SLNs (39,40,41).

A final and critical element in SLNB is careful palpation of the axilla and the submission of any palpably suspicious nodes as SLN. In our initial experience with SLNB (42), we reported that a false-negative rate of 14% defining the SLNs as blue and/or hot was reduced to 4.6% by defining the SLNs as blue and/or hot and/or palpable.

The axillary incision after SLNB is closed routinely without drainage. The morbidity of SLNB is less than that of ALND but is not zero. Patients may experience pain, seroma, hematoma, or infection. Blue dye may cause transient bluish-green discoloration of the skin and urine, blue urticaria in <1%, and anaphylactic reactions in <0.5% of patients (43).


Pathology

Our previous practice of intraoperative SLN frozen section and consent to proceed with ALND if SLN positive is now limited to patients outside the Z0011 selection criteria, largely those having a mastectomy or SLNB after neoadjuvant chemotherapy.

Axillary nodes have typically been examined by a single H&E–stained section, despite evidence that additional study (serial sections and/or immunohistochemical [IHC] stains for cytokeratins) could identify missed nodal metastases in a significant fraction of patients (44). These enhanced techniques—prohibitive for the examination of an entire ALND specimen—became feasible for SLNB and promised more accurate staging and selection of treatment. We now know from two large prospective trials (45,46) in which all treatment was based on the results of routine H&E staining that subsequent serial sectioning and IHC staining upstaged 10% to 16% of patients to SLN positive but that survival among those converted to node positive—90% of whom has already received systemic adjuvant therapy—was unaffected. One must conclude that SLN “ultrastaging” beyond routine H&E may result in overtreatment without affecting outcome.

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Aug 25, 2021 | Posted by in Aesthetic plastic surgery | Comments Off on Sentinel Node Biopsy and Axillary Dissection
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