A populational change in prognosis of patients diagnosed with locally advanced melanoma: Last glimpse before the introduction of adjuvant treatment in stage IIB/C.

e21575 Background: The treatment of early-stage melanoma is rapidly changing. Recent advancements include neoadjuvant treatment in stage III clinically detected disease and adjuvant treatment in stage IIB/C melanoma. In particular, adjuvant immunotherapy for IIB/C disease has become recently available. We took this opportunity to evaluate changes in outcomes in patients diagnosed with stage II and III melanoma. Methods: We have analyzed the accessible, retrospective data on patients diagnosed with melanoma between 2015 and 2022 who underwent sentinel lymph node biopsy or therapeutic lymph node dissection in high-throughput centers in Poland. The data on primary staging, patients’ demographics, and information on follow-up and overall survival (OS) were collected. A prespecified OS Cox model with non-linear terms for age, sex, stage (II vs. III), and availability of adjuvant treatment in stage III (i.e., since 2021) was fitted. Results: There were 1970 patients (45.2% female) included in this analysis. The mean age was 62 (range:14-97). The exact stage distribution and 3-year OS rates are presented in Table 1. Patients diagnosed with stage III melanoma before 2021 had worse prognoses than stage II patients (HR: 1.33, 95%CI: 1.11-1.60, p=0.002). Since then the prognosis for stage II patients did not improve (HR: 1.13, 95%CI: 0.89-1.45, p=0.325) while the prognosis in stage III melanoma became similar to stage II after the introduction of adjuvant therapy (HR: 1.09, 95% CI: 0.78-1.53, p = 0.607). Conclusions: The introduction of adjuvant treatment improved the OS of stage III melanoma patients in this nationwide study. The modern prognosis is similar to patients with stage II melanoma without adjuvant treatment, with excellent results in stage IIIA/IIIB cases. The practitioners should be cautious when discussing historical prognosis with their patients and it implies the necessity of changes in AJCC staging. Stage distribution and 3-year survival rates. Stage Number of patients Percentage of group 3 year survial rate (%) 95% Confidence Interval (%) IIA 352 17.9 86.5 82.9 - 90.3 IIB 378 19.2 76.5 72.2 - 81.2 IIC 443 22.5 59.9 55.3 - 64.8 IIIA 84 4.3 94.3 89.1 - 99.9 IIIB 132 6.7 94.6 90.5 - 98.9 IIIC 518 26.3 68.5 64.3 - 73.1 IIID 63 3.2 53.3 42.2 - 67.4