Intense Expression of EGFR L858R Characterizes the Micropapillary Component and L858R Is Associated with the Risk of Recurrence in pN0M0 Lung Adenocarcinoma with the Micropapillary Component.

BACKGROUND

Lung adenocarcinoma with the micropapillary (MP) component poses a higher risk of recurrence even when the MP component is not predominant. This study explored genetic features associated with highly malignant behavior of lung adenocarcinoma with the MP component.

METHODS

The MP and papillary (PaP) components were captured separately in three patients. Comprehensive mRNA expressions of somatic variants were compared between the MP and PaP components of each patient using next-generation sequencing (NGS). The protein expression of the NGS-detected variant was validated by immunohistochemistry. The prognostic impact of the detected variant was evaluated in 288 adenocarcinoma patients with resection of pN0M0.

RESULTS

In two cases, NGS suggested higher RNA expression of EGFR L858R in the MP component than in the PaP component (allele frequency, 0.485 vs. 0.155 and 1.000 vs. 0.526, respectively; P < 0.001 for both). Immunohistochemistry validated intense expression of L858R in the MP component of 27 MP-positive (MP+) patients. Among 288 pN0M0 patients, L858R was more frequently harbored in the MP+ patients than in the MP-negative (MP-) patients. The MP+ patients harboring L858R showed significantly worse recurrence-free survival (RFS) than the MP+ patients without L858R (median RFS 38.7 and 55.0 months, respectively; hazard ratio [HR] 3.004; 95% confidence interval [CI] 1.306-9.132; P = 0.012). Multivariate analysis of the MP+ patients showed that positive L858R status was associated with poorer RFS (HR 2.976; 95% CI 1.190-7.442; P = 0.020).

CONCLUSIONS

EGFR L858R was more frequently harbored in the MP+ adenocarcinoma patients than in the MP- adenocarcinoma patients. Intense expression of L858R in the MP component was suggested, and the MP+ patients harboring L858R were at comparatively higher risk of recurrence in the group with pN0M0 lung adenocarcinoma.