Oncologic Outcomes of Multi-Institutional Minimally Invasive Inguinal Lymph Node Dissection for Melanoma Compared with Open Inguinal Dissection in the Second Multicenter Selective Lymphadenectomy Trial (MSLT-II).

Background: Minimally invasive inguinal lymphadenectomy (MILND) is safe and feasible, but limited data exist regarding oncologic outcomes.

Methods: This study performed a multi-institutional retrospective cohort analysis of consecutive MILND performed for melanoma between January 2009 and June 2016. The open ILND (OILND) comparative cohort comprised patients enrolled in the second Multicenter Selective Lymphadenectomy Trial (MSLT-II) between December 2004 and March 2014.The pre-defined primary end point was the same-basin regional nodal recurrence, calculated using properties of binomial distribution. Time to events was calculated using the Kaplan-Meier method. The secondary end points were overall survival, progression-free survival, melanoma-specific survival (MSS), and distant metastasis-free survival (DMFS).

Results: For all the patients undergoing MILND, the same-basin regional recurrence rate was 4.4 % (10/228; 95 % confidence interval [CI], 2.1-7.9 %): 8.2 % (4/49) for clinical nodal disease and 3.4 % (6/179) for patients with a positive sentinel lymph node (SLN) as the indication. For the 288 patients enrolled in MSLT-II who underwent OILND for a positive SLN, 17 (5.9 %) had regional node recurrence as their first event. After controlling for ulceration, positive LN count and positive non-SLNs at the time of lymphadenectomy, no difference in OS, PFS, MSS or DMFS was observed for patients with a positive SLN who underwent MILND versus OILND.

Conclusion: This large multi-institutional experience supports the oncologic safety of MILND for melanoma. The outcomes in this large multi-institutional experience of MILND compared favorably with those for an OILND population during similar periods, supporting the oncologic safety of MILND for melanoma.