SAN DIEGO — Tumor thickness correlates with sentinel lymph node status in Merkel cell carcinoma and merits further investigation as a prognostic factor, Dr. Michael D. Alvarado reported in a poster at a symposium sponsored by the Society of Surgical Oncology.
Dr. Alvarado, of the H. Lee Moffitt Cancer Center & Research Institute in Tampa, Fla., presented a retrospective study of 62 Merkel cell carcinoma patients who underwent sentinel lymph node (SLN) biopsies at the center.
Investigators confirmed low recurrence rates in patients with negative SLN status, but found that patients with thicker tumors were more likely to have positive nodes.
Dr. Alvarado said that physicians at the cancer center began documenting thickness in 1998 to see whether it could be used to help stage patients, as is done in melanoma. “For Merkel cell carcinoma, no one really measures thickness,” he said. “The staging system is based on the diameter of the tumor and whether or not the nodes are positive.”
The study reviewed 62 patients who underwent SLN biopsies between 1994 and 2004. Among them, 41 patients had tumor thickness measurements available for review. Investigators found that 18 of the 41 patients (44%) had positive SLN. These patients also had thicker tumors. The average thickness was 8.9 mm in patients with positive nodes vs. 5.5 mm in those with negative nodes.
No positive nodes were found in five patients with tumors 2 mm or less in thickness, but “as you increase the thickness, the rate of positive sentinel lymph node goes up,” Dr. Alvarado said. (See box.)
He reported two nodal recurrences in the group of patients with tumors 2.1–4.9 mm in thickness and one regional recurrence in a patient whose tumor was in the 5–10 mm group.
One patient with a tumor thicker than 10 mm had a local recurrence. A third nodal recurrence occurred in a patient for whom tumor thickness had not been recorded.
All three patients with nodal recurrences had negative SLN status. The two local/regional recurrences were in SLN-positive patients, one of whom had radiation to both the primary and nodal basins and one of whom did not receive radiation therapy.
In an interview at the meeting, Dr. Alvarado said that further investigation is needed to determine which patients need SLN biopsy. Although Merkel cell carcinoma is often deadly if it recurs, Dr. Alvarado said that physicians must also be concerned about morbidity from the SLN procedure and the overtreatment of patients who are not likely to have a recurrence.
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