Adolescent Melanoma Stage IIIC under Anti-PD1 Adjuvant Therapy

immune checkpoint inhibitors (ICIs) refers to a specific response pattern that may mislead clinicians, interrumping a treatment to which patients are responding (2).We present a case series of patients treated with nivolumab-relatlimab with documented pseudoprogression.Methods: Patients with metastatic melanoma treated with nivolumab-relatlimab from July 2023 to January 2025, who experienced pseudoprogression were included.Patients received fixed-dose combinations of 160 mg relatlimab and 480 mg nivolumab, every 4 weeks.Treatment continued until disease progression or unacceptable toxicity occurred.Treatment response was evaluated clinically and through imaging, including whole-body contrast-enhanced 18F-FDG PET/CT scans Results: Clinical characteristics of the four patients are summarized in Table 1.The cohort included one male and three females, with a mean age of 60 years.All patients had BRAF wild-type tumors and a PD-L1 expression of <1%.Three patients received the combination as a second-line treatment, while one was treatmentnave.The median follow-up period from nivolumab-relatlimab treatment initiation was 10,3 months.Pseudoprogression occurred after a median of 3.5 cycles and primarily involved lymph nodes.However, two patients (B and C) exhibited pseudoprogression in lungs and liver, respectively.The treatment was generally well tolerated, with grade 1 asthenia as the most commonly reported immune-related adverse event.Patient A experienced grade 2 arthralgia, patient B had grade 2 gastritis, and patient C developed grade 2 adrenal insufficiency.Conclusions: Pseudoprogression under immunotherapy is not an uncommon phenomenon in real-world setting.However, it remains underreported and not fully understood.Further studies are needed to better characterize the features and frequency of pseudoprogression and to explore whether it may be associated with long-term responses or specific toxicities.Our observation suggest that pseudoprogression may occur more frequently under nivolumab-relatlimab treatment than with other ICIs, potentially reflecting a unique mechanism related to LAG-3 blockade