Clinical characteristics, prognosis, and immunotherapy outcome in pediatric melanoma: Analysis from a large Chinese cohort.

10050 Background: Malignant melanoma in children and adolescents is rare, with limited data on Chinese populations.To assess the clinical characteristics, survival, prognostic factors, and the efficacy of immunotherapy in a real-world cohort of Chinese pediatric patients with melanoma. Methods: This is a retrospective, cohort study included pediatric melanoma patients between February, 2005 and May, 2021, with a median follow-up time of 76.7 months. Data analyses were conducted in May, 2023. This study enrolled patients from Sun Yat-sen University Cancer Center, the biggest cancer institution in South China for cancer prevention, diagnosis and treatment. Inclusion criteria for this study were as follows: 1) histopathologically confirmed diagnosis of melanoma; 2) Age ≤18 year; 3) with complete clinical data on sex, age, histopathological features, etc. The exclusion criteria was secondary malignant melanoma. Main outcomes and measures were patient’s OS and EFS. Results: 43 patients were enrolled, with median age of 138.9 (range 13.1-215.0) months, including 30 cutaneous melanoma, 7 meningeal melanoma, 5 mucosal melanoma, and 1 uveal melanoma. The frequency of BRAF V600E mutation was 16.7% (4/24). Mismatch repair proteins were normally expressed (7/7), and the positive rate of programmed cell death ligand 1 expression was 55.6% (5/9). The event-free survival and overall survival of cutaneous, mucosal and meningeal melanoma were 46.7±9.1% vs 75.0±21.7% vs 16.7±15.2% ( P = 0.010), 65.5±8.9% vs 75.0±21.7% vs 16.7±15.2% (P< 0.001), respectively. Survival of cutaneous melanoma were associated with pathological type, ulceration, Clark level, disease spread, sentinel lymph node status, tumor stage and Ki-67 expression. 5 of 9 patients who were treated with PD-1 inhibitors (5 with PD-1 inhibitors alone, 3 with PD-1 inhibitors plus angiogenesis inhibitors, 1 with combination of anti-PD1, anti-angiogenic inhibitors plus chemotherapy) were evaluable with the overall response rate of 20%. The most common immune-related adverse event was hypothyroidism. Conclusions: This is the largest real-world study in pediatric melanoma patients in Asia. The prognosis of mucosal melanoma was favorable, followed by cutaneous melanoma, and meningeal melanoma had the worst prognosis. PD-1 antibody combined with angiogenesis inhibitors maybe a promising choice in pediatric melanoma.