Sentinel Lymph Node Biopsy for Squamous Cell Carcinoma Periprocedural Care

Updated: Dec 07, 2017
  • Author: Mark J Jameson, MD, PhD, FACS; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Periprocedural Care

Patient Education and Consent

Patients primarily are educated that sentinel lymph node (SLN) biopsy (SLNB) is most valuable for providing staging information to determine necessary treatment. It is important to educate patients that this is not a therapeutic technique, but rather a diagnostic procedure that allows the treatment team to plan more effective treatment. Risks of the surgery should be reviewed in the consent and should cover relevant risks of a neck dissection, including bleeding, infection, numbness, facial weakness, shoulder weakness, tongue weakness, injury to major vessels, chyle leak, and need for further surgery. The consent process needs to cover all potential procedures, particularly if a completion neck dissection may be performed within the same procedure. Patients also need to understand that additional surgery may be necessary based on the findings.

Patient education can be challenging regarding head and neck SLNB, owing to the "if, then" scenarios that are encountered depending on results. This can be improved by using preoperative single-photon emission computed tomography (SPECT) imaging, which better evaluates the position of the SLN(s) and allows surgeons to better predict the required procedure(s) compared with simple gamma imaging (see below). If reviewing SPECT images with patients, it must be made clear that although these images look similar to positron-emission tomography (PET-CT) imaging, the “hot spots” represent pathways to be evaluated and not sites of disease per se.

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Preprocedural Planning

As noted in other sections, the technique of SLNB is dependent on successful coordination between the surgeon and the nuclear medicine team, including consistent injection of radiotracer, imaging, and review of results with the surgeon. Many surgeons argue for frozen section analysis with completion neck dissection if a positive node is found. However, only limited nodal assessment can be performed using intraoperative evaluation. As with melanoma and breast cancer, SLNs excised from patients with head and neck squamous cell carcinoma (HNSCC) or cutaneous squamous cell carcinoma (cSCC) should undergo step-sectioning (see below) to thoroughly evaluate for occult microscopic disease.

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Equipment

A radiotracer probe is necessary to identify the lymph node intraoperatively. Some surgeons prefer to have a separate probe available prior to surgery to verify the planned area of dissection before preparing and draping the patient. Typical instrumentation and equipment for a neck dissection are adequate for this procedure. Nerve monitoring is not routinely used, but it may be useful in some settings (eg, intraparotid nodes, level V cervical nodes).

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Monitoring & Follow-up

If SLNB is performed without neck dissection, surgery is often performed in an outpatient setting, depending on the primary tumor resection. For SLNB performed with associated neck or other nodal basin dissection, patients are often admitted for 1-2 nights. Patients undergoing extensive dissection often have a drain placed postoperatively. Follow-up is typically performed 7-14 days postoperatively for wound check and to review results and discuss additional treatment.

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Preoperative Assessment

Physical examination and imaging are performed to evaluate the expected draining nodal basin of the HNSCC or cSCC being assessed. CT, MRI, ultrasound, and PET-CT are all commonly used in this process based on local resources, skillsets, costs, and clinical preferences.

In the setting of SLNB, imaging studies are performed to detect macroscopic lymph node metastases. If the imaging studies fail to show lymph node metastases, an SLNB is indicated depending on the likelihood of occult nodal disease from the primary tumor. For example, cT2N0 oral cavity SCC has an estimated risk of greater than 20% of occult cervical nodal disease and elective neck dissection has been advocated for these patients. In this setting, SLNB has the potential to avoid neck dissection in nearly 80% of cases. Similarly, while all cSCC in the head and neck carries only a 3-5% rate of metastasis, for advanced cSCC having high-risk features (eg, >2 mm thickness, incomplete excision, perineural invasion), risk of occult nodal disease increases with each high-risk feature. In this setting, SLNB can direct the need for local-only versus locoregional therapy.

Lymphoscintigraphy

Patients undergo lymphoscintigraphy up to 1 day prior to surgery. A maximum of 40 MBq technetium-99m–labeled human serum albumin (radiotracer (ie, AlbuRES, Nanocoll, Lymphoseek) is injected throughout the normal skin or mucosa surrounding the tumor edge and the dermis or submucosa on the deep aspect of the tumor in a volume of approximately 0.5-1 mL. A syringe with a permanently secured needle is used for injection, thereby preventing inadvertent spillage of radiotracer. Colloid is injected at as many points as necessary in an attempt to completely surround the tumor. For oral cavity injections, a mouthwash is used immediately following injection to prevent pooling or swallowing of residual radioactive material by the patient.

Static lymphoscintigraphy is performed at 15 minutes, 30 minutes, and 1 hour postinjection in two planes or until the appearance of radioactive nodes. Hot spots are usually seen 15 minutes postinjection. If nodes are still absent 1 hour after injection, the lymph nodes are too close to the injection site or radiocolloid has leaked out of the injection site. SPECT has largely replaced static lymphoscintigraphy in which an additional CT is performed onto which the lymphoscintigraphy is overlain to improve the anatomic localization of SLNs.

Multiple colloids are commonly used for lymphoscintigraphy: AlbuRES, Nanocoll, and, more recently, Lymphoseek, have gained favor, particularly in oral cavity SCC. AlbuRES has a mean particle size of 500 nm and is a slower-moving particle that remains in first-echelon (sentinel) nodes but requires a high density of terminal lymphatic vessels at the injection site. For these reasons, AlbuRES is the colloid of choice on the tongue and on the floor of the mouth. Nanocoll has a mean particle size of 50 nm and is a faster-moving colloid, which finds lymphatic vessels despite injection into tissues with low densities of terminal lymphatics. Nanocoll also moves readily from sentinel nodes to subsequent-echelon nodes. For these reasons, Nanocoll is the colloid of choice for primary tumors that are not located on the floor of the mouth or on the tongue. Lymphoseek (technetium Tc 99m tilmanocept) is a diethylenetriaminepentaacetic acid and mannose compound that rapidly diffuses within 15 minutes and stays present in tissue up to 30 hours. For this reason, it is gaining popularity in use for sentinel node mapping.

While historically blue dye and radioactive mapping had been combined, the consistent success of SLNB by radioactive mapping (across multiple studies approaching 95%) has led to preferential use. Intraoperative use of blue dye has many associated problems that have resulted in a decline in its use, particularly as the standard radiotracer technique has improved.

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