Thick melanomas without lymph node metastases: A forgotten group with poor prognosis

Introduction: Although adjuvant therapy is available for melanoma patients with sentinel lymph node (SLN) metastases (pN+), this is not the case for thick melanomas without SLN involvement (pN-). Objectives: We assessed overall and relative survival (OS, RS) in patients with >4.0 mm Breslow thickness (BT) pN- and pN + melanomas and ≤4.0 mm pN+ patients. Materials and methods: Clinicopathological data were retrieved from a cohort of >4.0 mm thick and/or pN + melanoma patients in The Netherlands from 2000 to 2014. OS and RS was compared using Kaplan-Meier-curves. A Cox-regression-model was developed to assess determinants of OS in >4.0 mm pN- patients. Results: In 54 645 patients, 3940 (7.2%) had >4.0 mm thick melanomas. SLN biopsy was performed in 1150 (29.2%) patients. Five-year OS was 70.5% for >4.0 mm pN- and 48.1% for >4.0 mm pN+ patients (p < 0.001), with a decreasing trend in OS for every mm BT. Five-year OS in 1877 ≤ 4.0 mm pN+ patients was 71.5%, which was not different from >4.0 mm pN- (p = 0.24). Higher age, higher BT category, ulceration and male gender were significantly associated with poor survival in >4.0 mm pN- patients. Conclusions: Thick pN- melanomas have a poor prognosis, comparable to that of less thick pN + melanomas, which is not accounted for in current guidelines. We encourage including these high-risk patients in adjuvant trials.