Background: Completion lymph node dissection (CLND) has long been the standard treatment for stage III melanomas identified as metastasis on the sentinel node (SN-positive). Two major changes occurred in 2017 and 2018, the change in the CLND criteria for SN-positive patients and the approval of several adjuvant therapies could revolutionize such management approach. However, their effects have not been fully investigated on the real-world outcomes of stage III melanoma patients. Therefore, we investigated the impact of these changes on the prognosis of Japanese stage III melanoma patients. Methods: Totally, 119 stage III, SN-positive melanoma patients were included. They were categorized into those diagnosed as SN-positive between January 2015 and June 2017 (pre-June 2017 group) and between July 2017 and December 2019 (post-July 2017 group). Recurrence-free survival (RFS), overall survival, and prognostic factors were analyzed. Results: The frequency of patients who received CLND was significantly higher in the pre-June 2017 group (p = 0.001), and those who received adjuvant therapy were significantly higher in the post-July 2017 group (p < 0.001). The 2-year RFS was 50.1% and 68.5% in the pre-June and post-July 2017 groups, respectively (p = 0.049). Cox proportional hazards model analysis for RFS showed that adjuvant therapies reduce the risk of recurrence (hazard ratio 0.37; 95% confidence interval 0.14–0.99; p = 0.047). Conclusion: Changes in the CLND criteria in SN-positive patients and the approval of adjuvant therapies for stage III melanomas have significantly impacted Japanese melanoma medicine. Adjuvant therapy tended to prolong patient’s RFS while omitting immediate CLND had no significant negative influence on it.
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