A Prognostically Significant Grading System for Lung Adenocarcinoma
JA Barletta, LR Chirieac. Brigham and Women's Hospital, Boston, MA
Background: Grading is a standard component of the pathology report for many tumor types and typically incorporates evaluation of tumor architecture, cytologic atypia, and for some tumors, mitotic count. Although grading has been shown to predict outcome for many tumor types, a prognostically significant grading scheme has not been established for lung adenocarcinoma. The aim of this study was to evaluate the prognostic value of each histologic parameter of tumor grading and to develop a prognostically significant grading system for lung adenocarcinoma.
Design: We studied lung adenocarcinomas from 85 consecutive patients. Tumors were evaluated for the percentage of solid growth pattern, the degree of cytologic atypia, and the mitotic count. For each parameter we determined the optimal cut-off value with the strongest association with overall survival. Based on the results of this analysis, tumor architecture was scored as 1 = solid growth pattern 80% or 2 = solid growth pattern >80% and cytologic atypia was scored as 1 = tumors with uniform nuclei or 2 = tumors with bizarre, enlarged nuclei of varied sizes. Because the mitotic count was not predictive of outcome (p=0.11), it was not incorporated into the scoring system. A total grading score was computed as the sum of the architecture score and cytologic atypia score (score 2 = well-differentiated, score 3 = moderately-differentiated, score 4 = poorly-differentiated). We compared the total grading scores with overall survival.
Results: The percentage of solid growth pattern and the degree of cytologic atypia were both statistically significant predictors of outcome. Patients with tumors with 80% solid growth had a median overall survival of 67.1 months and those with tumors with >80% solid growth had a median overall survival of 20.1 months (p=0.002). The median overall survival was 69.4 months for patients with tumors with mild cytologic atypia and 32.1 months for patients with tumors with severe cytologic atypia (p=0.01). The total grading score was a significant predictor of overall survival: patients with well-differentiated tumors had a median survival of 69.4 months, patients with moderately-differentiated tumors had a median survival of 39.5 months, and those with poorly-differentiated tumors had a median survival of 9.9 months (p<0.0001).
Conclusions: We have described a prognostically significant grading system for lung adenocarcinoma that incorporates the percentage of solid growth pattern and the degree of cytologic atypia. Additional prospective studies are needed to validate this grading system.
Monday, March 9, 2009 11:45 AM
Platform Session: Section F, Monday Morning