Age of Patients With Thin Melanomas a Consideration in SLNB Recommendations

Age may be an important factor in estimating lymph node positivity in thin melanoma, according to the results of a study published recently in JAMA Dermatology.

“Patient age was shown to be an important discriminant of nodal positivity among patients with mitogenic tumors 0.50 to 0.75 mm and 0.76 to 1.0 mm and nonmitogenic tumors 0.50 to 0.75 mm,” wrote Andrew J. Sinnamon, MD, of the Hospital of the University of Pennsylvania, and colleagues. “Patients 65 years or older were shown to have a lower risk of nodal disease across risk groups, and patients younger than 40 years had a higher risk.”

The majority of melanoma diagnosed each year are category T1 tumors at 1.0 mm thickness or less, according to the study. Although these patients have good prognosis, the use of sentinel lymph node biopsy (SLNB) to identify occult nodal disease is controversial. Guidelines by the National Comprehensive Cancer Network for SLNB are based on the probability of identifying nodal disease. The procedure is not recommended in patients with a node positivity threshold lower than 5%.

In this study, the researchers wanted to identify indicators of lymph node metastasis in thin melanoma. For the retrospective cohort study, Sinnamon and colleagues used data from the National Cancer Database from 2010 to 2013. The study included 8,772 patients with clinical stage I 0.50- to 1.0-mm thick melanoma who underwent wide excision and surgical evaluation of regional lymph nodes.

Nodal metastases were identified in 333 patients, for a positivity rate of 3.8% (95% CI, 3.4%–4.2%). Median age of patients with negative lymph nodes was 56 compared with 52 in patients with positive lymph node (P < .001).

A multivariable analysis showed that younger age, female sex, thickness of 0.76 mm or larger, increasing Clark level, mitoses, ulceration, and lymphovascular invasion were independently associated with positive lymph nodes.

The researchers performed classification tree analyses to identify high-risk groups for positivity. The analyses showed that patient age was an important risk stratifier. Specifically, patients younger than 40 with category T1b tumors 0.50 to 0.75 mm have a lymph node positivity rate of 5.6% (95% CI, 3.3%–8.6%). These patients would not generally be recommended for SLNB, the researchers noted. In contrast, patients aged 65 or older with T1b tumors 0.76 mm or larger, who would be recommended for SLNB, had a lymph node positivity rate of only 3.9%.

“Consideration of SLNB should be given for patients younger than 40 years with T1b tumors 0.50 to 0.75 mm,” the researchers wrote. “Conversely, guidelines may be overly permissive in older patients with tumors 0.76 mm or larger. Consideration of patient age may allow more appropriate allocation of SLNB, thus reducing both health care costs and possible unnecessary patient morbidity.”

In an editorial published with the study, Vernon K. Sondak, MD, of Moffitt Cancer Center in Tampa, Florida, and colleagues wrote that clinicians must improve their ability to individualize decision-making for the use of SLNB in in patients with thin melanoma.

“Even though it is premature to consider wholesale changes to our recommendations for SLNB, there is enough reason to believe that patient age is important for decision-making,” they wrote. “We should be studying not just T1 but also T2a melanoma cases to see if there are some patient subsets currently undergoing the procedure who may have a very low risk of nodal involvement. This could readily be accomplished through retrospective single-institution reviews that feature consistent and detailed histopathologic analysis, as well as using large, multi-institutional databases, like the National Cancer Database, that offer large numbers and reflect community as well as subspecialist practice.”