Sentinal node biopsy warranted in some cases of thin melanoma

NEW YORK (Reuters Health) - About 5% of patients with a thin cutaneous melanoma (1 mm thickness or less) harbor occult nodal metastases, and in these patients, sentinal lymph node biopsy (SLNB) may reveal important prognostic information, physicians report in the September Archives of Surgery.

"The incidence of melanoma ... is increasing worldwide, and up to 70% of new cases are thin lesions," write Dr. Donald L. Morton and his associates at the John Wayne Cancer Institute in Santa Monica, California. "Although these patients continue to do well overall, good outcomes are far from ensured."

To determine the value of sentinal node detection for these patients, the authors obtained information from their tertiary cancer center's comprehensive database for patients who underwent SLNB for thin primary cutaneous melanoma since 1991.

Of 631 patients, 31 (5%) had a tumor-positive sentinel node.

The 10-year disease-free and melanoma-specific survival rates were 96% and 98% for patients with negative sentinel nodes, versus 54% and 83% for tumor-positive sentinel nodes (p < 0.001 for both). Tumor-positive nodes were more common in patients age 50 and younger (p < 0.04).

On multivariate analysis, a tumor-positive sentinal node (p < 0.001), the presence of primary tumor ulceration (p = 0.003), and the head or neck as the primary tumor site (p < 0.001) were inversely associated with melanoma-specific survival.

"Additional prognostic information may be conveyed not only by tumor status of the sentinel node but also by quantification of tumor burden within the tumor-positive node," the investigators note. In their case series, 21% of patients with isolated tumor cells and 59% of those with micro- and macrometastasis developed recurrent disease.

Given the small proportion of patients who have occult nodal metastasis, how should clinicians advise patients with thin melanoma?

Dr. Morton's group suggests that all patients with invasive thin primary melanoma be counseled regarding the ability of SLNB to identify those with more advanced disease, as well as those at low risk of recurrence.

They conclude: "Younger patients with deeper lesions characterized by other adverse prognostic factors such as ulceration, elevated mitotic rate, and evidence of a vertical growth phase should be made aware of available evidence suggesting that they have a greater risk of occult nodal metastasis at the time of initial diagnosis and therefore might be more likely to benefit from SLNB."

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