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Lung cancer

New Grading System for Invasive Squamous Cell Carcinoma of the Lung Proposed

Strategic Insights

— 1 min read

The International Association for the Study of Lung Cancer (IASLC) Pathology Committee has proposed a new grading system for invasive squamous cell carcinoma of the lung (LUSC), a type of non-small cell lung cancer that accounts for approximately one-quarter of all lung cancers. The proposed system is based on tumor budding, a histopathologic feature that has been shown to be independently associated with recurrence-free survival (RFS) and overall survival (OS) in both training and test sets. The new grading system classifies tumors as low-grade (0-9 buds/0.785 mm²) or high-grade (10 buds/0.785 mm²), and has been validated in a test set comprising 827 LUSCs resected without neoadjuvant therapy from five institutions.

Key Takeaways:

  • The proposed grading system is based on tumor budding, which is the only variable independently associated with RFS and OS in both training and test sets.
  • The system classifies tumors as low-grade (0-9 buds/0.785 mm²) or high-grade (10 buds/0.785 mm²).
  • The proposed grading system was validated in a test set of 827 LUSCs resected without neoadjuvant therapy from five institutions.
  • The system demonstrated median RFS of 4.8 vs. 1.6 years for low-vs. high-grade tumors in the entire cohort and 7.2 vs. 3.4 years within stage I patients.
  • Interobserver agreement was moderate (Fleiss' kappa = 0.524).
  • The proposed grading system is reproducible across international datasets and practical for routine pathology.
  • The system differs from the standard grading system of the AJCC and UICC, which applies the same framework to all lung cancers.

Statistics:

  • Approximately one-quarter of all lung cancers are invasive squamous cell carcinoma (LUSC).
  • The proposed grading system was validated in a test set of 827 LUSCs resected without neoadjuvant therapy from five institutions.
  • Median RFS for low-grade tumors was 4.8 years, compared to 1.6 years for high-grade tumors in the entire cohort.
  • Median RFS for low-grade tumors was 7.2 years, compared to 3.4 years for high-grade tumors within stage I patients.

Sources:

  • Journal of Thoracic Oncology
  • International Association for the Study of Lung Cancer (IASLC) Pathology Committee
  • Massachusetts General Hospital

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