Interim results of the Multicenter Selective Lymphadenectomy Trial (MSLT-I) in clinical stage I melanoma

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7500 Background: Regional node management remains controversial because 80% of patients undergoing routine elective complete lymph node dissection (CLND) do not have nodal metastases. We developed lymphatic mapping and sentinel node biopsy (LM/SNB) to detect occult nodal metastases and thereby identify patients who might benefit from CLND. MSLT-I is an international, 17-center randomized trial to evaluate the accuracy and clinical impact of LM/SNB in patients with clinically localized cutaneous melanoma. Methods: Patients with primary melanoma were stratified by Breslow thickness (<1.2, 1.2–3.5, or >3.5 mm) and randomly assigned in a 40:60 ratio to wide excision (WE) followed by nodal observation (WEO), or to WE plus LM/SNB followed immediately by CLND only if the sentinel node (SN) contained tumor (SN+) by hematoxylin/eosin or immunostaining. Results: From 1/1/94 to 3/31/02, 797 patients were assigned to WEO and 1204 patients were assigned to LM/SNB. The third of 5 planned analyses was completed in October 2004 at a median follow-up of 54 months. Five-year disease-free survival was 78% with LM/SNB vs. 73% with WEO (p=0.01; HR 0.74). SN tumor status was the most important factor for 5-year survival of LM/SNB patients: survival was 88% for 944 SN- patients vs. 71% for 215 SN+ (p<0.0001, log rank). Nodal metastases were identified in 215 (19%) LM/SNB patients; nodal recurrence developed in 142 (18%) WEO patients. Five-year survival was significantly higher after immediate CLND for SN+ than delayed CLND for clinical nodal recurrence (71% vs. 55%; P = 0.0033, log rank; P = 0.0077, Cox multivariate). Conclusions: SN status is the most important prognostic factor in early-stage melanoma, and LM/SNB allows early and accurate detection of occult nodal metastases. Disease-free and melanoma-specific survival rates are significantly higher after immediate CLND for occult nodal metastases than delayed CLND for clinical nodal recurrence. LM/SNB should become standard for staging and assessment of prognosis in primary melanoma, and for identifying patients who may benefit from immediate CLND. MSLT-II will examine the therapeutic value of CLND vs. SNB alone for patients who are SN+. Supported by NIH CA29605. No significant financial relationships to disclose.