PII-038 - MULTICENTER PHARMACOKINETIC STUDY OF PEMBROLIZUMAB FOR NON-SMALL CELL LUNG CANCER IN OLDER ADULTS AGED OVER 75 YEARS.

T. Asao¹, Y. Yamanaka², T. Kurata², K. Watanabe³, Y. Hosomi³, H. Horinouchi⁴, Y. Ohe⁵, Y. Nakahara⁶, S. Saeki⁷, Y. Tsubata⁸, Y. Fujita⁹, J. Sakakibara-Konishi¹⁰, H. MIzugaki¹¹, M. Ouchi⁴, S. Yagishita⁴, A. Hamada⁴; ¹Juntendo University Hospital, Tokyo, Japan, ²Kansai Medical University Hospital, Osaka, Japan, ³Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital, Tokyo, Japan, ⁴National Cancer Center Research Institute, Tokyo, Japan, ⁵National Cancer Center Hospital, Tokyo, Japan, ⁶Kitasato University School of Medicine, Kanagawa, Japan, ⁷Kumamoto University Hospital, Kumamoto, Japan, ⁸Shimane University, Shimane, Japan, ⁹The Jikei University School of Medicine, Tokyo, Japan, ¹⁰Hokkaido University, Hokkaido, Japan, ¹¹Cancer Institute Hospital of JFCR, Tokyo, Japan.

Background: Pembrolizumab (Pem) is a key drug for the treatment of advanced or recurrent non-small cell lung cancer (NSCLC). However, there are limited data on Pem 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 Pem in older adults with NSCLC. Blood samples for PK analysis were collected immediately before Pem administration. Quantitative Pem 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, 70/29; performance status (PS) 0–1/2–3, 85/14; adeno/squamous/others, 62/25/12; stage I–III/IV/postoperative recurrence, 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.
In total, 77 blood samples were collected immediately before the second cycle (C1 trough). Although no clear association between Pem 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.

Conclusion: In older adults aged >75 years with NSCLC and low albumin levels and PS and a high number of metastatic organs, C1 trough of Pem is reduced and not expected to prolong PFS and OS.