5PSQ-013 Economic evaluation of the pembrolizumab dosing regimen by body weight in a second-level private hospital

<h3>Background and Importance</h3> Pembrolizumab is a monoclonal antibody directed against the PD-1 surface protein. Initial clinical trials established the 2mg/kg dosage as safe and effective, although later studies supported switching to a fixed dose (200 mg/cycle). The Therapeutic Positioning Report on pembrolizumab indicates that efficacy and safety are comparable and do not present clinically significant variations between the two regimens. <h3>Aim and Objectives</h3> The objective of this study is to analyse, in real clinical practice, the effectiveness of weight-based dosing of the active ingredient, and the potential opportunity cost compared to fixed dosing. <h3>Material and Methods</h3> Pharmacoeconomic study of 6.2 months duration (25 September 2023 to 31 March 2024) in a second-level private hospital. All patients who received any regimen with pembrolizumab were included. The variables studied were: sex, age, weight, diagnoses, administered cycles, cost of treatment with pembrolizumab with fixed dose and without weight adjustment. The data were obtained from the electronic medical record and the electronic prescription program Farmis-Oncofarm. <h3>Results</h3> Twenty-four patients were included (54.17% women) with a median age of 68.83 (IQR, 62.25 to 87.00) years. The average weight was 70.21 kg (SD, 8.91). The most frequent diagnosis was non-squamous non-small-cell lung cancer, accounting for 50.00%, followed by squamous non-small-cell lung cancer and malignant breast neoplasm, both at 8.33%. The average number of chemo-immunotherapy cycles administered per patient was 5.083 (standard deviation). The cost per session at a fixed dose is 7,132.00 euros, while adjusted for weight it is 5,781.63 euros, representing a saving of 18.93%. This translates to a follow-up cost of 939, 639.00 euros (39,151.625 euros per patient), resulting in a gross saving of 183,651.00 euros. This saving is accompanied by the advantage that the effectiveness and safety of the treatment are not affected according to published studies. <h3>Conclusion and Relevance</h3> Weight-based dosing of pembrolizumab generates a significant opportunity cost without impacting efficacy or safety, making it the most efficient strategy in routine clinical practice. <h3>References and/or Acknowledgements</h3> Canadian Agency for Drugs and Technologies in Health. CADTH technology review: optimal use 360 report: dosing and timing of immuno-oncology drugs. Published online November 2019. <h3>Conflict of Interest</h3> No conflict of interest