Abstract 148P
Background
A histologic grading system for lung adenocarcinoma was recently proposed by the International Association for the Study of Lung Cancer (IASLC). This study evaluated the risk associated with histologic Grade 3 within Stage 1A (1AG3) lung adenocarcinoma.
Methods
From January 2010 to December 2017, 709 cases of nonmucinous adenocarcinoma classified as Stage 1A or 1B according to the 8th TNM staging system and surgically resected at Seoul St. Mary’s Hospital were reviewed. Tumor-containing slides were examined to assess the proportions of lepidic, acinar, papillary, solid, micropapillary, and complex glandular patterns. Grading was performed based on the IASLC-proposed criteria. Overall survival (OS) and disease-free survival (DFS) were analyzed using Kaplan-Meier curves and Cox proportional hazards regression.
Results
In survival analysis, within Stage 1A, the Grade 3 (1AG3) group exhibited significantly worse OS (HR: 12.68, 95% CI: 4.03–50.76, p < 0.001) and DFS (HR: 8.53, 95% CI: 4.51–16.73, p < 0.001) compared to the Grade 1/2 group. No significant differences in OS (HR: 0.82, p=0.648) or DFS (HR: 0.80, p=0.399) were observed between the 1AG3 and Stage 1B groups. When Stage 1B was further stratified into Grade 1/2 (1BG1/2) and Grade 3 (1BG3) groups, 1AG3 demonstrated a trend towards worse prognosis compared to 1BG1/2, as reflected by a higher HR and visual inspection of survival curves, although the p-value was not statistically significant (p > 0.05). For tumors ≤3 cm with pleural invasion, a recognized basis for upstaging, risks were higher than Stage 1A (HR: 4.89 [2.01–11.58] for OS and HR: 4.54 [2.75–7.40] for DFS) but remained lower than those associated with Grade 3 tumors (HR: 12.68 for OS and HR: 8.53 for DFS).
Conclusions
The IASLC histologic grading system has been validated for risk stratification. However, our findings suggest that Stage 1A lung adenocarcinomas with Grade 3 histology align more closely with the risk profile of Stage 1B. This parallels the current staging principle, wherein pleural invasion prompts upstaging to Stage 1B regardless of tumor size. By incorporating histologic grading into risk assessment, further stratification of high-risk patients may refine clinical management strategies and improve outcomes.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.