Real-world patterns and temporal trends of first-line immunotherapy use in metastatic NSCLC in Brazil according to PD-L1 expression.

e20631 Background: First-line (1L) treatment of metastatic NSCLC has evolved rapidly with the incorporation of immune checkpoint inhibitors (IO), administered either as monotherapy or combined with chemotherapy (CT). While PD-L1 expression is a key biomarker guiding treatment selection, real-world data describing temporal trends and PD-L1–driven decisions among patients receiving IO in Latin America remain scarce. Methods: This retrospective, observational, multicenter study included patients aged ≥18 years with unresectable or metastatic NSCLC treated with 1L systemic therapy between January 2021 and December 2023 at seven Brazilian cancer centers. Patients with non-epithelial histology and neuroendocrine tumors were excluded. Clinical, pathological, and biomarker data were collected using standardized eCRFs. The present analysis focused on patients receiving 1L immunotherapy with or without chemotherapy. Descriptive statistics were used. Associations were assessed using Fisher’s exact or Student’s t-test, as appropriate. OS was estimated using the Kaplan–Meier method and explored using univariable Cox regression. Analyses were conducted using R (v4.4.2). Results: Among 500 included patients, median age was 69.5 years; 61% were current/former smokers, 61% had < 2 comorbidities, and 80% had ECOG 0–1. Adenocarcinoma was the predominant histology (80%), and 82% had metastatic disease at diagnosis. PD-L1 expression was < 1% in 30.8%, 1–49% in 29.4%, and ≥50% in 20.8%. Overall, 245 patients (49.0%) received IO-based 1L therapy. CT+IO was the most frequently used regimen (85.0%), predominantly platinum-based chemotherapy plus pembrolizumab, whereas IO monotherapy accounted for 15.0% of cases. Treatment choice was significantly associated with PD-L1 status (p < 0.001): 56.8% of patients receiving IO monotherapy had PD-L1 ≥50%. Dual IO-based regimens were used in a minority of patients, mainly among those with PD-L1 < 1%. Use of intensified IO-based combinations increased over time, from 1.4% in 2021 to 13.2% in 2023. PD-L1 expression showed a trend toward improved OS with increasing expression levels. Conclusions: In this real-world Brazilian cohort, PD-L1 expression played a central role in guiding first-line immunotherapy selection for metastatic NSCLC, supporting its continued clinical relevance in routine practice. However, the heterogeneity of outcomes across PD-L1 subgroups underscores the need for additional predictive biomarkers to further refine patient selection and optimize immunotherapy-based treatment strategies.