Different dosing strategies of pembrolizumab in the treatment of NSCLC: A real-world retrospective observational study.

Urska Janzic University Clinic Golnik, Golnik, Slovenia info_outline Urska Janzic, Zala Rus, Lea Knez

Authors Urska Janzic University Clinic Golnik, Golnik, Slovenia info_outline Urska Janzic, Zala Rus, Lea Knez Organizations University Clinic Golnik, Golnik, Slovenia, University of Ljubljana, Faculty of Pharmacy, 1000 Ljubljana, Slovenia, University of Ljubljana, Faculty of Pharmacy, Ljubljana, Slovenia Abstract Disclosures Research Funding No funding sources reported Background: Immune checkpoint inhibitors lack a dose-response relationship, allowing optimisation of dosing strategies that may reduce drug use. Pembrolizumab received its initial regulatory approval for the treatment of non-small cell lung cancer (NSCLC) at weight-based dosing (2 mg/kg every 3 weeks (Q3W)), as employed in pivotal clinical trials demonstrating its efficacy and safety. This dosing regimen was later replaced by the currently approved flat-dosing (200 mg Q3W or 400 mg Q6W) in all indications, potentially increasing drug use. This retrospective observational study evaluates differences in pembrolizumab use for different dosing strategies in a real-world patient cohort. Methods: Overall, 124 advanced NSCLC patients, treated with first-line pembrolizumab monotherapy at a single institution, were included. During the observation period, pembrolizumab flat-dosing was employed, with possible extensions of treatment administrations. Patient and treatment data were obtained from medical records. Duration of treatment was calculated from day 1 of first cycle to last day of last cycle, excluding treatment delays due to adverse events. Pembrolizumab use was calculated for 3 dosing strategies: i) as actually received, ii) as flat-dosing, iii) as body-weight dosing, capped at 200 mg Q3W. It is presented as median dose Q3W and cummulative dose in the whole cohort. Results: Included patients had a median weight of 73 kg (IQR: 65-84) and received a total of 1600 mg of pembrolizumab (IQR: 800-3600) over 24 weeks (IQR: 12-60). The median pembrolizumab dose was i) 190 mg Q3W (IQR: 172-200) as actually received by patients, and would be ii) 200 mg Q3W (IQR: 200-200) in case of flat dosing, and iii) 146 mg Q3W (IQR: 130-168) in case of body-weight dosing. Overall, total pembrolizumab dose in the whole cohort was i) 283,600 mg actually used, and would be ii) 327,800 mg in flat-dosing, and iii) 251,200 mg body-weight dosing, resulting in a 23.4% reduction of drug use in weight-adjusted vs flat-based dosing. Conclusions: Pembrolizumab dosing adjusted to body weight, as initially approved, would reduce drug use vs the currently approved flat-dosing, reaching nearly a 25% reduction in our cohort of patients.