| Serial KL-6 Changes in PD-1/PD-L1 Inhibitor–Related Pneumonitis in NSCLC: A Single-Center Prospective Pilot Study |
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Jae Kyeom Sim1, Juwhan Choi1, Sung Won Chang1, Sang Hyuk Kim1, Jee Youn Oh1, Kyung Hoon Min1, Gyu Young Hur1, Hwan Seok Yong2, Jae Jeong Shim1, Sung Yong Lee1 |
1Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Internal Medicine, Korea University Guro Hospital, Korea University College of Medicine, Seoul, Korea
2Department of Radiology, Korea University Guro Hospital, Korea University College of Medicine, Seoul, Korea |
Correspondence:
Sung Yong Lee,
Email: syl0801@korea.ac.kr
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Received: 7 August 2025 • Revised: 3 October 2025 • Accepted: 11 December 2025 |
| Abstract |
Background
Programmed cell death 1/programmed cell death ligand 1 (PD-1/PD-L1) inhibitors are effective therapies for non-small cell lung cancer (NSCLC), but their use can lead to pneumonitis, which may be severe. The purpose of this study is to investigate the utility of Krebs von den Lungen-6 (KL-6) for the prediction and diagnosis of PD-1/PD-L1 inhibitor-related pneumonitis in patients with NSCLC.
Methods
We conducted a prospective observational study at a university-affiliated tertiary hospital in Korea from February 2022 to June 2023. Baseline KL-6 levels were measured immediately prior to the initiation of PD-1/PD-L1 inhibitor therapy. In patients who develop pneumonitis, KL-6 levels were measured every 1–2 weeks starting at pneumonitis onset. In patients without pneumonitis, KL-6 levels were measured every six weeks. We compared the clinical characteristics and serial KL-6 levels between the pneumonitis and non-pneumonitis groups.
Results
A total of 18 patients were enrolled, of whom 11 developed pneumonitis. Baseline KL-6 levels did not significantly differ between the pneumonitis and non-pneumonitis groups (261 U/ml vs 373 U/mL, P = 0.375). In the pneumonitis group, KL-6 levels generally followed an upward trend, with a median level of 412 U/mL at the time of pneumonitis onset. In contrast, KL-6 levels did not demonstrate clear overall change in the non-pneumonitis group.
Conclusions
In this pilot cohort, baseline KL-6 was not clearly associated with PD-1/PD-L1 inhibitor–related pneumonitis in patients with NSCLC, whereas post-baseline increases were more frequently observed among patients who developed pneumonitis (including all-cause pneumonitis cases). |
| Key Words:
Non-small cell lung cancer, PD-1/PD-L1 inhibitor, Pneumonitis, Krebs von den Lungen-6 |
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