79P Real-world overall survival after planned alternative dosing for pembrolizumab in the treatment of NSCLC: A nationwide retrospective non-inferiority analysis

Early clinical trials and pharmacological studies show comparable pembrolizumab results with doses lower than the marketed 200 mg Q3W. Following a recommendation from the Dutch Society of Medical Oncology, many Dutch hospitals implemented an alternative, partially lower, weight-based dosing regimen for pembrolizumab. This analysis compares the overall survival (OS) of the alternative pembrolizumab dosing regimen to standard dosing using a nationwide registry in non-small cell lung cancer (NSCLC) patients. Forty hospitals in the Dutch Medication Audit and Dutch Lung Cancer Audit treated 1996 patients with NSCLC with first line pembrolizumab (mono- or combination therapy) between Jan 1st, 2021 and Mar 31st, 2023. 604 patients in 21 hospitals received alternative dosing and 1362 patients in 19 hospitals received standard dosing, as described in the table. A Cox proportional hazard model with selected covariates was used to compare the OS between alternative and standard dosing regimens. The non-inferiority margin was set at 1.2 for OS (Table). Distribution of age, gender and treatment combinations were similar for both groups, comorbidity score was higher in the standard dosing group. Median daily pembrolizumab dose in the alternative dosing group was 7.14 mg/day (interquartile range (IQR): 5.48-8.04 mg/day) vs. 9.15 mg/day (IQR: 8.33-9.52 mg/day) in the standard dosing group. The OS of the alternative dosing regimen was non-inferior compared to standard dosing (adjusted hazard ratio 0.833, 95% confidence interval: 0.692-1.003).Table: 79PReduced and standard pembrolizumab dose levels and OSAlternative dosing (n=604)Standard dosing (n=1362)WeightDose (Q3W/Q6W)Proportion of patientsDose (Q3W/Q6W)Dose levels< 65 kg200/400 mg24.1%200/400 mg65-90 kg150/300 mg50.2%≥ 90 kg200/400 mg25.7%Median survival (IQR)18.1 months (15.4-23.0)15.2 months (14.2-17.2) Open table in a new tab This real-world analysis on a nationwide registry showed that the OS of NSCLC patients after alternative partially lower pembrolizumab dosing was non-inferior to standard pembrolizumab dosing. Alternative pembrolizumab dosing regimens can lead to substantial cost reductions.