Prognostic impact of pattern-based grading system by the new IASLC/ATS/ERS classification in Asian patients with stage I lung adenocarcinoma

Objectives: We examined the prognostic effect of the grading system based on the new IASLC/ATS/ERS classification in an Asian cohort of patients with early-stage lung adenocarcinoma.

Materials and methods: Patients with a lung adenocarcinoma less than 3cm in diameter that had undergone complete anatomic resection, diagnosed with pT1a-2aN0M0 consecutively from 2004 to 2013, were enrolled. All specimens were reviewed according to the new IASLC/ATS/ERS classification. The growth patterns were divided into three major categories: grade 1 for lepidic growth, grade 2 for acinar and papillary patterns, and grade 3 for solid and micropapillary patterns. Each tumor was then graded according to the modified grading system, the final score being the sum of the two most predominant grades. The correlations of clinical and pathological factors with disease-free survival (DFS) and overall survival (OS) were evaluated.

Results: In total, 201 adenocarcinomas were eligible for score grading. Only 37 (18.4%) patients had a pure pathological growth pattern. Higher stage, greater tumor diameter, positive lymphovascular invasion, and a higher score were associated with shorter DFS. In contrast, stage no longer had a significant impact on OS in a multivariable analysis. Acinar/papillary-predominant tumors with a score of 3 or 4 were associated with better survival than those with a score of 5 (5-year DFS rate: 64.68 vs. 44.18%, HR=2.19, 95% CI: 1.24-3.87; 5-year OS rate: 85.61 vs. 68.59%, HR=3.03, 95% CI: 1.25-7.32).

Conclusion: The architectural scores may help to stratify survival differences among certain predominant growth subtypes of adenocarcinoma.