Prognostic associations of PD-L1 expression and BAP1 loss in pleural mesothelioma: a retrospective single-center cohort from Colombia

Our plain-English summary of Prognostic associations of PD-L1 expression and BAP1 loss in pleural mesothelioma: a retrospective single-center cohort from Colombia, by R. Brugés, C. Carvajal, A. Luna-Meza, et al (Frontiers in Oncology, 2026).

The study

• Authors: R. Brugés, C. Carvajal, A. Luna-Meza, M. Núñez, A. Navarrete, R. Parra-Medina
• Journal: Frontiers in Oncology
• Published: 2026;16:1920798
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Evidence on the prognostic associations of programmed death-ligand 1 (PD-L1) and BRCA1-associated protein 1 (BAP1) in pleural mesothelioma (PM) remains inconsistent, and joint data from Latin American cohorts are limited. We evaluated these biomarkers in a Colombian cohort.

Methods: This retrospective single-center cohort included adults with histologically confirmed PM treated at the Instituto Nacional de Cancerología, Bogotá, from January 2011 through December 2023. PD-L1 was quantified using tumor proportion score (TPS), with ≥1% as the primary threshold; BAP1 was classified as retained or lost by nuclear immunoreactivity. Overall survival (OS) was measured from pathologic diagnosis to death. Event-free survival (EFS) was measured from diagnosis to first documented progression or death; patients without an event were censored at last contact. Kaplan-Meier methods and separate multivariable Cox models were used.

Results: Sixty-seven patients were included; 60/67 (89.6%) had locally advanced or metastatic disease. PD-L1 TPS ≥1% was present in 26/67 (38.8%), and BAP1 loss in 47/61 evaluable tumors (77.0%). All 67 patients died. Median OS was 9.20 months (95% CI, 6.11-14.13), and median EFS was 6.51 months (95% CI, 5.49-9.13). PD-L1 TPS ≥1% was not clearly associated with OS (adjusted HR, 1.03; 95% CI, 0.57-1.86) or EFS (adjusted HR, 1.11; 95% CI, 0.62-2.00). BAP1 loss also showed no clear adjusted association with OS (HR, 1.57; 95% CI, 0.78-3.16) or EFS (HR, 1.65; 95% CI, 0.82-3.33).

Conclusions: Neither PD-L1 TPS ≥1% nor BAP1 loss showed a clear adjusted association with survival. These jointly measured estimates extend the evidence from an underrepresented Latin American population but require external validation; the exploratory ≥5% and ≥10% analyses were based on only 14 and 7 patients, respectively.

Copyright © 2026 Brugés, Carvajal, Luna-Meza, Núñez, Navarrete and Parra-Medina.

In plain English

This retrospective study from one cancer hospital in Bogotá, Colombia, looked at 67 adults with pleural mesothelioma seen between 2011 and 2023. The authors tested tumors for PD-L1 (main cutoff: 1% or more of tumor cells staining) and for BAP1 protein loss. PD-L1 of 1% or more was found in 26 of 67 patients, and BAP1 loss in 47 of 61 assessable tumors. Asbestos exposure was documented in the medical records of 32 of 67 patients. All 67 patients died, and median overall survival was 9.20 months (95% CI 6.11 to 14.13). After adjustment for age, sex, performance status, histologic subtype and stage, neither PD-L1 of 1% or more (hazard ratio 1.03; 95% CI 0.57 to 1.86) nor BAP1 loss (hazard ratio 1.57; 95% CI 0.78 to 3.16) was clearly associated with overall survival. Poorer performance status (ECOG 2 to 3) was associated with shorter survival. Exploratory, unadjusted analyses at higher PD-L1 cutoffs involved only 14 and 7 patients. The authors concluded that neither marker showed a clear adjusted association with survival and that the results require external validation.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Retrospective single-center cohort study
• Who was studied: 67 adults (aged 18 or older) with histologically confirmed pleural mesothelioma seen at the Instituto Nacional de Cancerología, Bogotá, Colombia, January 2011 to December 2023. 52/67 were male, the mean age was 64.9 years, and 57/67 had epithelioid histology.
• Exposure: The main variables studied were tumor biomarkers: PD-L1 tumor proportion score (1% or more as the primary threshold) and BAP1 loss. Asbestos exposure was taken only from the medical record and was documented in 32/67 patients (asbestos only 10, asbestos and tobacco 22). No fiber types, jobs or doses were reported.
• Main results:
  • PD-L1 TPS of 1% or more was present in 26/67 patients (38.8%). BAP1 loss was present in 47/61 evaluable tumors (77.0%).
  • All 67 patients died. Median overall survival for the whole cohort was 9.20 months (95% CI, 6.11 to 14.13), and median event-free survival was 6.51 months (95% CI, 5.49 to 9.13).
  • In adjusted models (64 patients), PD-L1 TPS of 1% or more was not clearly associated with overall survival (adjusted HR 1.03; 95% CI, 0.57 to 1.86; p = 0.918) or event-free survival (adjusted HR 1.11; 95% CI, 0.62 to 2.00; p = 0.717).
  • In adjusted models (58 patients), BAP1 loss was not clearly associated with overall survival (adjusted HR 1.57; 95% CI, 0.78 to 3.16; p = 0.205) or event-free survival (adjusted HR 1.65; 95% CI, 0.82 to 3.33; p = 0.160).
  • ECOG performance status 2 to 3 (versus 0 to 1) was associated with higher hazards in all four models. In the PD-L1 model for overall survival, the adjusted HR was 4.53 (95% CI, 2.19 to 9.36; p less than 0.001).
  • Exploratory, unadjusted analyses: PD-L1 TPS of 5% or more (14 patients) had HR 1.93 (95% CI, 1.04 to 3.60) for overall survival. TPS of 10% or more (7 patients) had HR 2.13 (95% CI, 0.95 to 4.74; p = 0.065) for overall survival. The authors did not interpret these as a dose-response.
• The authors' conclusion: The authors concluded that neither PD-L1 TPS of 1% or more nor BAP1 loss showed a clear adjusted association with survival, and that these estimates from a Latin American population require external validation.
• Limitations the authors state:
  • The retrospective, single-center design in a referral setting limits generalizability and may introduce selection bias.
  • The cohort was small. The BAP1 models had fewer than 10 events per parameter, giving wide confidence intervals and possible model instability.
  • Residual confounding remains likely despite adjustment.
  • Asbestos exposure came from clinical records and may be under-recorded.
  • No external cohort was available to validate the findings.

Topics

Medical terms in this study, explained in our Lexicon: PD-L1, BAP1, Pleural Mesothelioma, Biomarker, Overall Survival.

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