Observation policy for sentinel node metastasis of melanoma: Comparative study with completion lymph node dissection in Japanese patients.

Based on the results of international multicenter randomized trials, completion lymph node dissection for patients with sentinel lymph node-positive melanoma is no longer routinely recommended. However, clinicians should take into consideration racial and medical resource differences when applying this evidence to clinical practice in Japan. To evaluate the clinical validity of the observation policy of omitting completion lymph node dissection, we retrospectively surveyed patients with sentinel lymph node-positive melanoma between 2002 and 2020 at Niigata Cancer Center Hospital. A total of 59 patients were categorized into the observation group (n = 19) and completion lymph node dissection group (n = 40). Newly developed anticancer agents, including targeted therapy and immunotherapy, were more commonly used in the observation group than in the completion lymph node dissection group as either adjuvant therapy (31.6% vs. 5.0%) or post-recurrence therapy (100% vs. 34.8%). The median overall survival in the observation group (not reached) was significantly longer than that in the completion lymph node dissection group (95.0 months; p = 0.02), which was mainly attributed to the difference in post-recurrence overall survival. There was no significant difference in recurrence-free survival between the two groups (p = 0.63). Although the use of new anticancer agents leads to bias, this study demonstrates that observation without prompt completion lymph node dissection provides a favorable overall survival without increasing the risk of recurrence compared with completion lymph node dissection. The observation policy for patients with sentinel lymph node-positive melanoma patients is considered to be clinically valid in real-world medical practice.