WCLC 2025 - Posters & ePosters-PT1.07.01 IASLC Multidisciplinary Recommendations for Pathological Response Evaluation of Resected Lymph Nodes After Neoadjuvant Therapy in NSCLC

PT1.07.01 IASLC Multidisciplinary Recommendations for Pathological Response Evaluation of Resected Lymph Nodes After Neoadjuvant Therapy in NSCLC

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The IASLC Pathology Committee led an interdisciplinary Delphi study to establish standardized recommendations for evaluating pathological response in resected lymph nodes (LNs) after neoadjuvant therapy in non-small cell lung cancer (NSCLC). Recognizing that pathological response in LNs correlates with long-term outcomes but lacks standardized assessment, the recommendations aim to harmonize LN evaluation across clinical trials and real-world practice, complementing the 2020 IASLC guidelines on the primary tumor.<br /><br />The consensus, achieved through two voting rounds involving medical oncologists, thoracic surgeons, radiologists, and pathologists, includes 13 key recommendations with at least 85% agreement. Highlights include:<br /><br />1. Surgical teams must inform pathology labs of neoadjuvant therapy to guide specimen processing.<br /><br />2. Definitions standardize terminology: Complete Pathologic Response (CPR) requires no viable tumor cells in lung and LNs; any viable tumor in LNs excludes CPR. Major Pathologic Response (MPR) is ≤10% viable tumor cells in the primary tumor; MPR(N) applies when primary tumor shows ≤10% viability but LNs contain metastatic carcinoma.<br /><br />3. Treatment response assessment in all sampled LNs should use IASLC criteria established for primary tumors—quantifying viable tumor, stroma, and necrosis—and be reported separately from primary tumor response.<br /><br />4. Eyeball microscopic estimation is deemed acceptable; largest metastatic deposit size per LN station should be recorded.<br /><br />5. Psammoma bodies or acellular mucin alone should not be considered viable tumor.<br /><br />6. Standard TNM staging and margin (R) status principles apply; direct tumor extension into LNs is staged as nodal metastasis.<br /><br />7. Complete histologic submission of intraparenchymal and separately submitted LN stations is recommended, with exceptions for very large metastases.<br /><br />8. Immunohistochemistry is reserved for selected cases to confirm suspected viability when morphology is ambiguous.<br /><br />These recommendations address gaps in LN response evaluation, aiming to improve prognostic accuracy and facilitate uniform reporting in NSCLC post-neoadjuvant therapy. They build on prior IASLC guidelines focused on primary tumors and reflect broad multidisciplinary expert consensus.

Asset Subtitle

Sabina Berezowska

Meta Tag

Speaker Sabina Berezowska

Topic Early-Stage Non-small Cell Lung Cancer

Keywords

IASLC Pathology Committee

Delphi study

pathological response

resected lymph nodes

neoadjuvant therapy

non-small cell lung cancer

standardized recommendations

Complete Pathologic Response

Major Pathologic Response

NSCLC staging