In July of this year, both the American Society of Clinical Oncology (ASCO) and the Society for Surgical Oncology (SSO) released evidence-based recommendations on the use of sentinel lymph node biopsy (SLNB) in patients with melanoma.
The guidelines are as follows:
- SLNB is recommended for all patients with melanoma tumors of intermediate thickness (between 1 and 4 mm): Studies have shown that the technique is useful for identifying small nearby metastases in these patients, who account for about one-third of all melanoma cases. SLNB detects cancer in the sentinel node in about 18% to 26% of these patients, according to the guideline authors.
- Evidence is insufficient to recommend routine SLNB for patients with thin melanoma tumors (less than 1 mm): Thin melanomas are the most common form of melanoma, and can usually be cured through surgical removal of the primary tumor. While SNLB is not necessary in most cases, the guideline recommendations note that it may be considered in select patients with thin melanomas who have certain high-risk factors, such as an ulcerated tumor or rapidly dividing cancer cells.
- SLNB for patients with thick melanoma tumors (greater than 4 mm) may be recommended: Thick melanomas are more uncommon than the above two types, but are considered more likely to spread elsewhere in the body. While there are few studies focusing on the use of SLNB in patients with thick melanomas, use of SLN biopsy in this population may be recommended for staging purposes and to facilitate regional disease control.
- Completion lymph node dissection is recommended for all patients with a positive SLNB: Complete removal of the remaining lymph nodes has been shown to prevent or limit further cancer spread in these patients. While it is not yet known whether this approach improves survival, the authors note that an ongoing study, the Multicenter Selective Lymphadenectomy Trial II, is expected to help resolve that question.
As a surgeon who specializes in melanoma, I would like to address some of the grey areas that still exist in SLNB. Overall, the procedure itself in experienced hands has very low morbidity. My general routine is for the patient to undergo lymphoscintigraphy with technetium the morning of surgery to evaluate the draining lymph node basin(s). The patients then undergo general anesthesia. I inject lymphazurin blue intradermally around the primary melanoma intraoperatively. The procedure itself takes approximately 30 to 40 minutes and is accomplished through a 2 to 3 cm incision.
The main risks, which I counsel the patients about, are postoperative seroma, which generally resolve on their own; temporary irritation of the nerves supplying the axilla or anterior thigh; infection; and a very low incidence of chronic lymphedema (I quote them a 5% to 7% chance of this). My current algorithm is to perform SLNBs for all patients with a melanoma >0.76 mm in thickness, or any melanoma with high-risk features including ulceration or mitotic rate >1 mm2.
There are some nuances related to the guidelines, which I would like to comment on:
SLNB is recommended for all patients with melanoma tumors of intermediate thickness (between 1 and 4 mm): I agree with this guideline. There are online nomograms that I frequently utilize when evaluating my patients to discuss more precisely their individual chance of having a positive sentinel lymph node.
Evidence is insufficient to recommend routine SLNB for patients with thin melanoma tumors (less than 1 mm): The majority of patients will present with thin melanomas <1mm in thickness. The wording on the guideline is somewhat vague. As I feel there is low-morbidity of SLNB and approximately 6% to 8% of patients with melanomas >0.76 mm will have a positive SLNB, I generally use this depth as my cutoff to offer patients the biopsy. You have to individualize your discussion with these patients. I believe a stronger consideration should be made for SLNB in younger patients. I would consider high-risk features to include ulceration or dermal mitotic rate. I also consider SLNB if the initial primary biopsy demonstrated a thin melanoma with a positive deep margins. At my institution, we have all slides reviewed prior to treatment specifically looking at these factors, which may change the overall treatment plan.
SLNB for patients with thick melanoma tumors (greater than 4 mm) may be recommended: Although the risk of both lymphatic and hematogenous spread of melanoma in patients with thick tumors (>4mm) is high, our standard is to offer SLNB in these patients. It provides additional important prognostic information, and patients frequently have localized disease with no evidence of metastatic disease on staging imaging. All of these patients are referred to medical oncology at our institution for discussion of adjuvant therapy or a clinical trial.
As with any set of guidelines, one must understand the nuances and have an educated discussion with their patients regarding the risks and benefits of a procedure and come to a mutually agreeable plan. This is certainly true for SLNB for melanoma. I believe it would be wrong to exclude all patients from having a SLNB based on a thin lesion (<1mm) alone.
Dr. Farma is an Assistant Professor of Surgical Oncology at Fox Chase Cancer Center in Philadelphia, PA.