Multicenter pharmacokinetic study of pembrolizumab for non-small cell lung cancer in adults aged older than 75 years

e21098 Background: Pembrolizumab (Pemb) is a key drug for the treatment of advanced or recurrent non-small cell lung cancer (NSCLC). However, there are limited data on Pemb use in older adults aged > 75 years with NSCLC, especially in terms of pharmacokinetics (PK). Methods: This open-label multicenter observational study aimed to evaluate real-world data on the safety, efficacy, and blood concentrations of Pemb (both monotherapy and combination therapies) in older adults with NSCLC. Blood samples for PK analysis were collected immediately before Pemb administration. Quantitative Pemb concentrations were measured by liquid chromatography-mass spectrometry. Results: We enrolled 100 patients from July 2019 to September 2020; one patient was excluded due to stage migration. Patient characteristics were as follows: median age, 78 (75–87) years; male/female ratio, 70/29; performance status (PS) 0–1/2–3, 85/14; adenocarcinoma/squamous cell carcinoma/others, 62/25/12; stage I–III/IV/postoperative recurrence (TNM 7th edition), 9/60/30; PD-L1 TPS < 1%/1%–49%/≥50%, 12/31/48; and monotherapy/combination therapy, 65/34. The best overall efficacy was CR/PR/SD/PD (7/40/32/20), and the response rate was 47.5%. The median progression-free survival (PFS) and overall survival (OS) were 8.0 and 19.0 months, respectively. The adverse event profile was generally similar to that reported in previous studies. In total, 77 blood samples were collected immediately before the second cycle (C1 trough). Although no clear association between Pemb concentrations and patient background was found, PFS and OS were significantly shortened in the population with low C1 trough, a population characterized by lower PS, high number of metastatic organs at the beginning of treatment, and low blood albumin level. Conclusions: In older adults aged > 75 years with NSCLC and low albumin levels and PS and a high number of metastatic organs, C1 trough of Pemb is reduced and not expected to prolong PFS and OS. Clinical trial information: UMIN000036606 .