BACKGROUND: Immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment but come with high costs. Alternative ICI dosing strategies could reduce costs without losing efficacy. However, clinical efficacy data are lacking. METHODS: In this retrospective cohort trial, consecutive patients with advanced non-small cell lung cancer (NSCLC) who received ≥1 cycle pembrolizumab±chemotherapy at two tertiary institutions were included. Hybrid dosed patients received either 100, 150 or 200 mg pembrolizumab every 3 weeks or double every 6 weeks depending on their weight: <65 kg, 65-90 kg or >90 kg, respectively. Standard-of-care flat dosed patients received 200 mg every 3 weeks or 400 mg every 6 weeks. Overall survival (OS) and progression-free survival (PFS) were assessed by Kaplan-Meier estimation, compared by log-rank test and HRs were calculated with the Cox proportional hazards model in both unweighted and inverse probability of treatment weighted (IPTW) cohorts. Non-inferiority margin was set at an HR of 1.15. RESULTS: In total, 375 patients and 391 patients were included and median follow-up was 43.1 and 61.0 months in the hybrid and flat dose cohort, respectively. OS was non-inferior in the hybrid dose cohort compared with the flat dose cohort: median 17.7 months (95% CI 14.9 to 20.9) vs 11.8 months (95% CI 9.3 to 13.8, HR 0.76, 95% CI 0.65 to 0.90, p<0.0001 for non-inferiority). After correcting for confounders by IPTW, OS remained non-inferior (HR 0.76, 95% CI 0.63 to 0.91, p<0.0001 for non-inferiority). PFS in the hybrid cohort was also non-inferior to the flat dose cohort with a median of 6.4 months (95% CI 5.7 to 7.7) vs 4.6 months (95% CI 3.9 to 5.5, HR 0.82, 95% CI 0.70 to 0.96, p<0.0001 for non-inferiority). In total, 26.2% (or 52.5 mg per cycle, p<0.0001) pembrolizumab was saved in the hybrid dose cohort accounting to US$36 331.36 per patient. CONCLUSIONS: In this retrospective analysis of a large cohort of advanced NSCLC patients treated with pembrolizumab±chemotherapy, OS of hybrid dosed patients was non-inferior to flat dosed patients. OS remained non-inferior after correcting for possible confounding factors. This hybrid regimen resulted in significant savings of pembrolizumab and costs.
