SAN ANTONIO – In a large but nonrandomized group of patients with primary melanoma, sentinel node biopsy significantly prolonged disease-free survival, but offered no prolongation of distant metastases free- or melanoma-specific survival.
Researchers at the Melanoma Institute Australia in North Sydney evaluated survival among 5,567 patients who from 1992 to 2008 underwent wide local excision with or without sentinel node biopsy (SNB) for a primary melanoma that was at least 1 mm thick, Clark level IV or V, or had ulceration. Median follow-up was 3.5 years.
Among the 2,803 patients who underwent SNB, 390 had a positive sentinel node (14%), followed by early complete lymph node dissection. Of the 2,413 patients with a negative sentinel node, 88 experienced regional lymph node recurrence (3.6%) and underwent delayed total lymph node dissection. This resulted in a false-negative rate for SNB of 18.4%, Mr. Stijn van der Ploeg, M.Sc., reported.
Among the 2,765 patients who underwent wide local excision with nodal observation using ultrasound, 378 experienced regional lymph node recurrence (13.7%) and underwent delayed total lymph node dissection.
In univariate analysis, patients who underwent SNB had significantly improved disease-free survival and regional lymph node metastases-free survival (both P value less than .001), but no prolongation in distant metastases-free survival (P = .85) or melanoma-specific survival (P = .49), said Mr. van der Ploeg, now a doctoral student at Erasmus Medical Center in Rotterdam, The Netherlands.
When patients were stratified by tumor thickness, melanoma-specific survival significantly improved in SNB patients with tumors 1.2 mm to 3.5 mm thick (P = .01).
Mr. van der Ploeg pointed out that there were significant differences between the two groups. The SNB group had younger patients, more nodular melanomas, and more distant recurrence as the first site of recurrence, while the observation group had thinner primary tumors, more tumors located in the head and neck, and more nodal recurrences as the first site of recurrence.
After adjusting for these and other differences – including gender, age, histological subtype, mitotic rate, Clark level, and ulceration – the researchers observed no significant benefit for SNB vs. observation for melanoma-specific survival among patients in all thickness subgroups analyzed, he said.
Finally, in univariate analysis, early complete lymph node dissection failed to significantly improve distant metastases-free survival or melanoma-specific survival among SNB-positive patients of all thickness subgroups. There was a trend toward improved distant metastases free-survival favoring early vs. late dissection among patients with intermediate-thickness melanoma (P = .060).
"Our study suggests that patients with intermediate-thickness melanomas 1.2 [mm] to 3.5 [mm] are most likely to have therapeutic benefit from undergoing sentinel node biopsy," Mr. van der Ploeg concluded.
He added that the final results of the Multicenter Selective Lymphadenectomy Trial-1 (MSLT-1) are awaited with great interest, to better define melanoma patient subgroups most likely to obtain a survival benefit from SNB.
Interim analyses from MSLT-1 have confirmed that disease-free and distant disease-free survival are improved with SNB among patients with intermediate-thickness melanomas, but the long-running trial has failed to show a definitive overall survival advantage for the procedure.
During a discussion of the Australian study, audience members asked what techniques were used for SNB, remarking that the false-negative rate of 18% is well above the 4% rate reached by many groups today. Mr. van der Ploeg said the false-negative rate has fallen over time with more experience to 15%, and that surgeons use blue dye, but not the 10% rule during lymph node mapping.
The authors reported no disclosures.