Association of BAL Fluid T-Cell Immune Activity With Tumor PD-L1 Expression and Its Prognostic Value: A Prospective Observational Study

This prospective observational study aims to evaluate whether immune profiles of T-cell subsets in bronchoalveolar lavage fluid can complement tumor PD-L1 expression, assessed by immunohistochemistry in tumor tissue specimens, in predicting clinical outcomes in patients with advanced lung cancer. Although tumor PD-L1 expression measured on tissue biopsies is widely used to guide immunotherapy decisions, its predictive value is limited by spatial heterogeneity and sampling variability. By analyzing activated, exhausted, and regulatory T-cell populations in bronchoalveolar lavage fluid and examining their association with tissue-based tumor PD-L1 expression, this study seeks to determine whether combining local immune biomarkers with PD-L1 expression improves the prediction of treatment response and survival in patients receiving standard-of-care systemic therapy.

Study Overview

• Status: Not yet recruiting
• Conditions: Lung Neoplasms; Tumor Immune Microenvironment

Detailed Description

Tumor PD-L1 expression assessed by immunohistochemistry on tumor tissue specimens is an established biomarker for selecting immune checkpoint inhibitor therapy in lung cancer; however, its clinical utility is limited by intratumoral heterogeneity, temporal variability, and dependence on the size and location of tissue biopsy samples. As a result, tissue-based PD-L1 expression alone does not fully capture the immune context of the tumor microenvironment or reliably predict treatment response and prognosis in all patients.

Bronchoalveolar lavage fluid provides access to the local pulmonary immune microenvironment and contains immune cells that may reflect tumor-immune interactions more directly than peripheral blood. Prior studies suggest that T-cell populations in bronchoalveolar lavage fluid share phenotypic characteristics with tumor-infiltrating lymphocytes and may serve as surrogate indicators of local antitumor immune activity. However, the relationship between bronchoalveolar lavage T-cell immunophenotypes, tissue-based tumor PD-L1 expression, and clinical outcomes has not been comprehensively evaluated in a prospective setting.

This single-center prospective observational cohort study enrolls adult patients with suspected or confirmed stage IV lung cancer who are undergoing clinically indicated bronchoscopy as part of routine diagnostic or management procedures. Residual bronchoalveolar lavage fluid obtained during standard-of-care bronchoscopy is analyzed using multicolor flow cytometry to quantify T-cell subsets, including activated, exhausted, and regulatory populations defined by surface marker expression. Tumor PD-L1 expression is evaluated by immunohistochemistry performed on diagnostic tumor tissue specimens obtained as part of routine clinical care and analyzed both as a continuous variable and by predefined expression categories.

Participants receive standard systemic anticancer therapy according to current clinical guidelines, including immune checkpoint inhibitor-based regimens when indicated. Clinical outcomes, including objective response rate, progression-free survival, and overall survival, are prospectively collected from electronic medical records. The study examines correlations between bronchoalveolar lavage T-cell immunophenotypes and tissue-based tumor PD-L1 expression, as well as whether stratification based on combined immune profiling provides improved prognostic information compared with tumor PD-L1 expression alone.

By integrating local immune profiling from bronchoalveolar lavage fluid with tumor PD-L1 expression assessed in tissue specimens, this study seeks to identify complementary biomarkers that may enhance risk stratification and refine prognostic assessment in advanced lung cancer, potentially informing future approaches to personalized immunotherapy.

• Study Type: Observational
• Enrollment (Estimated): 60

Contacts and Locations

• Study Contact: Name: Deog Kyeom Kim, MD, PhD; Phone Number: +82-2-870-2228; Email: kimdkmd@gmail.com
• Study Contact Backup: Name: Heemoon Park, MD; Phone Number: +82-2-870-3439; Email: coramdeo33@gmail.com

Study Locations

• South Korea
  • Dongjak-gu
    • Seoul, Dongjak-gu, South Korea, 07061
      • SMG-SNU Boramae Medical Center
      • Contact: Deog Kyeom Kim, MD, PhD; Phone Number: +82-2-870-2228; Email: kimdkmd@gmail.com
      • Contact: Heemoon Park, MD; Phone Number: +82-2-870-3439; Email: coramdeo33@gmail.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

The study population comprises adult patients evaluated at SMG-SNU Boramae Medical Center in Seoul, Republic of Korea. Participants are drawn from routine clinical practice and include patients undergoing clinically indicated bronchoscopy as part of the diagnostic evaluation or management of suspected or confirmed stage IV lung cancer. All clinical assessments, treatments, and follow-up are performed according to standard-of-care practice based on current clinical guidelines, and no additional diagnostic or therapeutic procedures are introduced solely for research purposes.

Description

Inclusion Criteria:

• Adults aged 19 years or older
• Patients with suspected or histologically confirmed stage IV lung cancer based on clinical and radiologic findings
• Scheduled to undergo clinically indicated bronchoscopy with bronchoalveolar lavage as part of routine clinical care
• Able and willing to provide written informed consent

Exclusion Criteria:

• Receipt of treatment for acute lower respiratory tract infection (including pneumonia or fungal infection) within 4 weeks prior to bronchoscopy
• History of solid organ transplantation or hematopoietic stem cell transplantation
• Current use of systemic immunosuppressive therapy
• Current or planned use of biologic immunomodulatory agents
• Known autoimmune disease requiring systemic immunosuppressive treatment
• Pregnant women
• Patients with recurrent stage IV lung cancer after prior definitive therapy

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

Advanced Lung Cancer Cohort; Adults with suspected or confirmed stage IV lung cancer undergoing clinically indicated bronchoscopy with bronchoalveolar lavage. Participants are enrolled prospectively as a single observational cohort, and no treatment assignment or intervention is determined by the study. Bronchoalveolar lavage fluid is collected for immune profiling by flow cytometry, and study analyses stratify participants post hoc according to tumor PD-L1 expression levels and bronchoalveolar lavage T-cell immunophenotypes.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Correlation Between Bronchoalveolar Lavage T-cell Immunophenotypes and Tumor PD-L1 Expression	The primary outcome is the association between T-cell immunophenotypes quantified in bronchoalveolar lavage fluid by multicolor flow cytometry and tumor PD-L1 expression assessed by immunohistochemistry. T-cell subsets include activated, exhausted, and regulatory T-cell populations defined by surface marker expression (e.g., PD-1, TIM-3, CD39, CD28, CD25, and CD127). Tumor PD-L1 expression is evaluated as the percentage of PD-L1-positive tumor cells and analyzed as a continuous variable and by predefined categories (<1%, 1-49%, ≥50%).	At baseline, prior to initiation of systemic anticancer therapy

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Differences in Bronchoalveolar Lavage T-cell Immunophenotypes Across Tumor PD-L1 Expression Categories	This outcome compares bronchoalveolar lavage T-cell subset distributions among participants stratified by tumor PD-L1 expression categories (<1%, 1-49%, and ≥50%). T-cell immunophenotypes are assessed by flow cytometry and include proportions of activated, exhausted, and regulatory T-cell subsets.	At baseline, prior to initiation of systemic anticancer therapy
Objective Response Rate by Combined Tumor PD-L1 Expression and Bronchoalveolar Lavage T-cell Immunophenotypes	Objective response rate is defined as the proportion of participants achieving complete or partial response according to RECIST version 1.1. Objective response rates are evaluated using combined stratification by tumor PD-L1 expression categories and bronchoalveolar lavage T-cell immunophenotype profiles, and compared with response rates stratified by tumor PD-L1 expression alone to assess improvement in treatment response prediction.	From treatment initiation to first radiologic response assessment (typically 6-12 weeks)
Progression-Free Survival by Combined Tumor PD-L1 Expression and Bronchoalveolar Lavage T-cell Immunophenotypes	Progression-free survival is defined as the time from initiation of systemic anticancer therapy to disease progression or death from any cause, whichever occurs first. Progression-free survival is analyzed using combined stratification based on tumor PD-L1 expression categories (<1%, 1-49%, ≥50%) and bronchoalveolar lavage T-cell immunophenotype profiles. Survival outcomes using the combined stratification are compared with those based on tumor PD-L1 expression categories alone to evaluate the incremental prognostic value of bronchoalveolar lavage immune profiling.	From treatment initiation to disease progression or death, up to approximately 24 months
Overall Survival by Combined Tumor PD-L1 Expression and Bronchoalveolar Lavage T-cell Immunophenotypes	Overall survival is defined as the time from initiation of systemic anticancer therapy to death from any cause. Overall survival is analyzed according to combined stratification by tumor PD-L1 expression categories and bronchoalveolar lavage T-cell immunophenotype profiles. Survival outcomes derived from the combined model are compared with those based on tumor PD-L1 expression alone to assess whether bronchoalveolar lavage immune profiling improves prognostic discrimination.	From treatment initiation to death from any cause, up to approximately 24 months

Collaborators and Investigators

• Sponsor: Seoul National University Hospital
• Collaborators: SMG-SNU Boramae Medical Center

Publications and helpful links

General Publications

• Kim IA, Hur JY, Kim HJ, Kim WS, Lee KY. Extracellular Vesicle-Based Bronchoalveolar Lavage Fluid Liquid Biopsy for EGFR Mutation Testing in Advanced Non-Squamous NSCLC. Cancers (Basel). 2022 May 31;14(11):2744. doi: 10.3390/cancers14112744.
• Kalkanis A, Papadopoulos D, Testelmans D, Kopitopoulou A, Boeykens E, Wauters E. Bronchoalveolar Lavage Fluid-Isolated Biomarkers for the Diagnostic and Prognostic Assessment of Lung Cancer. Diagnostics (Basel). 2022 Nov 25;12(12):2949. doi: 10.3390/diagnostics12122949.
• Masuhiro K, Tamiya M, Fujimoto K, Koyama S, Naito Y, Osa A, Hirai T, Suzuki H, Okamoto N, Shiroyama T, Nishino K, Adachi Y, Nii T, Kinugasa-Katayama Y, Kajihara A, Morita T, Imoto S, Uematsu S, Irie T, Okuzaki D, Aoshi T, Takeda Y, Kumagai T, Hirashima T, Kumanogoh A. Bronchoalveolar lavage fluid reveals factors contributing to the efficacy of PD-1 blockade in lung cancer. JCI Insight. 2022 May 9;7(9):e157915. doi: 10.1172/jci.insight.157915.
• Mariniello A, Tabbo F, Indellicati D, Tesauro M, Rezmives NA, Reale ML, Listi A, Capelletto E, Carnio S, Bertaglia V, Mecca C, Consito L, De Filippis M, Bungaro M, Paratore C, Di Maio M, Passiglia F, Righi L, Sangiolo D, Novello S, Geuna M, Bironzo P. Comparing T Cell Subsets in Broncho-Alveolar Lavage (BAL) and Peripheral Blood in Patients with Advanced Lung Cancer. Cells. 2022 Oct 14;11(20):3226. doi: 10.3390/cells11203226.
• Mansour MSI, Hejny K, Johansson F, Mufti J, Vidis A, Mager U, Dejmek A, Seidal T, Brunnstrom H. Factors Influencing Concordance of PD-L1 Expression between Biopsies and Cytological Specimens in Non-Small Cell Lung Cancer. Diagnostics (Basel). 2021 Oct 18;11(10):1927. doi: 10.3390/diagnostics11101927.
• Ben Dori S, Aizic A, Sabo E, Hershkovitz D. Spatial heterogeneity of PD-L1 expression and the risk for misclassification of PD-L1 immunohistochemistry in non-small cell lung cancer. Lung Cancer. 2020 Sep;147:91-98. doi: 10.1016/j.lungcan.2020.07.012. Epub 2020 Jul 13.
• Gniadek TJ, Li QK, Tully E, Chatterjee S, Nimmagadda S, Gabrielson E. Heterogeneous expression of PD-L1 in pulmonary squamous cell carcinoma and adenocarcinoma: implications for assessment by small biopsy. Mod Pathol. 2017 Apr;30(4):530-538. doi: 10.1038/modpathol.2016.213. Epub 2017 Jan 6.

Study record dates

Study Major Dates

• Study Start (Estimated): January 1, 2026
• Primary Completion (Estimated): December 31, 2027
• Study Completion (Estimated): December 31, 2027

Study Registration Dates

• First Submitted: December 29, 2025
• First Submitted That Met QC Criteria: December 29, 2025
• First Posted (Estimated): January 12, 2026

Study Record Updates

• Last Update Posted (Estimated): January 12, 2026
• Last Update Submitted That Met QC Criteria: December 29, 2025
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Keywords: Immune Checkpoint Inhibitors; Overall Survival; Progression-Free Survival; Flow Cytometry; Programmed Cell Death 1 Ligand 1; Predictive Biomarkers; Treatment Response; Tumor Immune Microenvironment; Bronchoalveolar Lavage Fluid; Tumor-Infiltrating T Lymphocytes
• Additional Relevant MeSH Terms: Neoplasms by Site; Neoplasms; Respiratory Tract Diseases; Lung Diseases; Respiratory Tract Neoplasms; Thoracic Neoplasms; Lung Neoplasms
• Other Study ID Numbers: BRMH 30-2025-48

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data will not be shared publicly. The study includes sensitive clinical, immunologic, and imaging data derived from bronchoalveolar lavage samples and other patient-specific assessments, and no formal data-sharing infrastructure or governance plan has been established at the time of trial registration. However, de-identified individual participant data that underlie the results reported in peer-reviewed publications may be made available after publication upon reasonable request to the corresponding author, subject to appropriate data use agreements, institutional approval, and compliance with applicable ethical and privacy regulations.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No