IASLC Tumor Budding Grade Identifies High-Risk Patients With Resected Lung Squamous Cell Carcinoma

(SEOUL, Republic of Korea —Tuesday, September 15th, 9:45 a.m. Korea Standard Time) — A newly proposed International Association for the Study of Lung Cancer (IASLC) tumor budding-based grading system successfully identified patients with resected lung squamous cell carcinoma (SqCC) at higher risk of poor outcomes and showed potential to help guide selection for adjuvant chemotherapy, according to research presented at the IASLC 2026 World Conference on Lung Cancer (WCLC).

The study independently validated the 2025 IASLC two-tier grading system, which classifies resected lung SqCC as low grade or high grade based solely on tumor budding. Investigators retrospectively reviewed 585 consecutive patients who underwent curative-intent upfront resection at Yonsei University Medical Center from 2015 through 2022.

“Our findings show that the newly proposed IASLC tumor budding-based grading system can identify patients with resected lung squamous cell carcinoma who have a poorer prognosis, while also suggesting that high-grade patients may be the group most likely to derive benefit from adjuvant chemotherapy,” said T.H. Hong of Yonsei University School of Medicine in Seoul. “Prospective multicenter validation will be important to confirm its potential role in treatment selection.”

Among the 585 patients, 520 (88.9%) had low-grade tumors, and 65 (11.1%) had high-grade tumors. High-grade disease was associated with a significantly more advanced pathologic stage distribution. High-grade tumors were independently associated with worse overall and disease-free survival on multivariable analysis.

Investigators also examined patients with pathologic stage IB–III disease who were eligible for adjuvant treatment. Across this subgroup, there was no overall disease-free survival benefit from adjuvant chemotherapy. When patients were stratified by tumor budding grade, however, low-grade patients showed no benefit, while high-grade patients demonstrated a clinically meaningful trend toward benefit from adjuvant chemotherapy. Exploratory genomic profiling in a case-matched subset (n=100) showed no difference in global genomic instability between grades, but identified significant enrichment of PI3K pathway alterations in low-grade tumors and directional enrichment of truncating TP53 mutations in high-grade tumors, suggesting divergent oncogenic programs between grades.

The authors concluded that the IASLC tumor budding–based grading system provided independent prognostic stratification and was associated with distinct patterns of adjuvant chemotherapy outcomes and genomic alterations. These findings extend the clinical and biological relevance of the newly proposed grading system. Prospective multicenter validation is warranted to confirm its potential role in treatment stratification.

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About the IASLC:
The International Association for the Study of Lung Cancer (IASLC) is the only global organization dedicated solely to the study of lung cancer and other thoracic malignancies. Founded in 1974, the association's membership includes more than 10,000 lung cancer specialists across all disciplines in over 100 countries, forming a global network working together to conquer lung and thoracic cancers worldwide. The association also publishes the Journal of Thoracic Oncology, the primary educational and informational publication for topics relevant to the prevention, detection, diagnosis, and treatment of all thoracic malignancies. Visit www.iaslc.org for more information.

About the WCLC:
The WCLC is the world’s largest meeting dedicated to lung cancer and other thoracic malignancies, attracting nearly 7,000 researchers, physicians, and specialists from more than 100 countries. The goal is to increase awareness, collaboration and understanding of lung cancer, and to help participants implement the latest developments across the globe. The conference will cover a wide range of disciplines and unveil several research studies and clinical trial results. For more information, visit https://wclc.iaslc.org/.