WCLC 2025 - Posters & ePosters-EP.08.49 Accurate Pathologic Response Assessment of Lung Adenocarcinoma Treated With Neoadjuvant Targeted Therapy

EP.08.49 Accurate Pathologic Response Assessment of Lung Adenocarcinoma Treated With Neoadjuvant Targeted Therapy

Pdf Summary

This study from Shanghai Pulmonary Hospital addresses the challenge of accurately assessing residual viable tumor cells (RVT) in lung adenocarcinoma patients treated with neoadjuvant targeted therapy. Distinguishing RVT from non-neoplastic reactive proliferative epithelium in resection specimens is difficult using traditional methods alone. The researchers aimed to improve accuracy and reproducibility by combining hematoxylin and eosin (H&E) staining with immunohistochemistry (IHC) and molecular testing.<br /><br />The study included 32 patients treated between 2018 and 2023, all harboring oncogenic abnormalities: 18 with ALK rearrangements, 12 with EGFR mutations, and 2 with ROS1 fusions. Pathologic response in tumor beds and metastatic lymph nodes was evaluated using H&E staining, ALK Ventana-D5F3 IHC for ALK-positive patients, and PCR detection for EGFR and ROS1 abnormalities.<br /><br />Results classified pathologic response as non-major (non-MPR, n=11), major (MPR, n=9), and complete pathologic response (CPR, n=12). Assessments using H&E, IHC, and molecular tests were largely consistent. However, in some CPR cases, subtle atypical epithelial cells were difficult to classify: for ALK-positive cases, IHC confirmed these as residual tumor cells, while in EGFR-mutant cases, PCR demonstrated that similar atypia represented reactive pneumocyte hyperplasia rather than tumor.<br /><br />The study concludes that while H&E staining remains a practical initial method, integrating ALK IHC and PCR molecular testing significantly enhances accuracy and reproducibility in identifying RVT after neoadjuvant targeted therapy. This multimodal approach aids precise pathologic assessment, facilitating better evaluation of treatment response in lung adenocarcinoma patients with specific oncogenic drivers.

Asset Subtitle

Shaoling Li

Meta Tag

Speaker Shaoling Li

Topic Local-Regional Non-small Cell Lung Cancer

Keywords

lung adenocarcinoma

residual viable tumor cells

neoadjuvant targeted therapy

hematoxylin and eosin staining

immunohistochemistry

molecular testing

ALK rearrangements

EGFR mutations

ROS1 fusions

pathologic response assessment