Oncogenic Alterations in Histologically Negative Lymph Nodes Are Associated with Prognosis of Patients with Stage I Lung Adenocarcinoma

Abstract

Background: Survival of patients with stage I non-small cell lung cancer (NSCLC) varies greatly. We sought to explore whether presence of oncogenic alterations in histologically-negative lymph nodes (LNs) can be of prognostic significance in stage I lung adenocarcinoma (LUAD). Methods: Genomic analysis of oncogenic alterations was applied to 123 stage I LUAD tumors. The same genomic variants identified in primary tumors were examined in corresponding histologically-negative LNs. Results: A total of 102 (82.9%) patients had at least one canonical oncogenic alteration detected in primary tumors, and 57 LNs from 12 patients (11.8%) were found to carry the identical oncogenic alterations detected in the corresponding primary tumor tissues, including EGFR mutations (six cases), KRAS mutations (three cases), ALK fusion (one case), BRAF mutation (one case) and HER2 & NRAS co-mutations (one case). None of these LNs was found to have occult tumor cells by routine pathological assessment or immunohistochemistry staining using antibodies against pan-cytokeratins (AE1/AE3) and the epithelial marker Ber-EP4. The detection rate of oncogenenic alterations in LN was significantly higher in RAS-mutant tumors than EGFR mutant tumors (36.36% verse 7.41%, p = 0.017). Patients with oncogenic alterations in LN showed inferior disease-free survival (DFS, p = 0.025) and overall survival (OS, p = 0.027). Furthermore, patients with RAS-mutations detected in LN had the worst DFS and OS (p = 0.001). Among the 11 patients with RAS mutation in primary tumors, DFS and OS in the four patients with mutations detected in LN were significantly shorter than the remaining seven patients without mutations LN (DFS, p = 0.001, OS, p = 0.002). Conclusions: Genomic analysis has the potential to detect oncogenic alterations in regional LNs for localized LUAD and presence of oncogenic alterations in regional LN may be associated with inferior clinical outcome of stage I LUAD, particularly for certain molecular subgroups. ClinicalTrials.gov ID NCT04266691.

Keywords: genomic analysis; lymph node; oncogenic alteration; prognosis; stage I lung adenocarcinoma.

Figure 1

Study scheme. A total of 140 patients were initially quired and 17 patients were excluded because of receiving neoadjuvant chemotherapy (n = 8), R1 resection (n = 3), inadequate tumor specimens (n = 4) or identification of LN metastasis at the time of FFPE block sectioning. Finally, the remaining 123 eligible patients were subjected to subsequent analyses.

Figure 2

Disease-free survival (A) and overall survival (B) of patients with LN molecular alterations of different oncogenic mutations. Different colors represent those molecular alterations in different LN stations. Arrows indicate that patients had no recurrence or death.

Figure 3

Survival of 102 histologically stage I LUAD with or without molecular alterations in LN. Comparison of DFS (A) and OS (B) between patients with molecular alterations in LN (LN^MT, green line) versus those without molecular alterations in LN (LN^Negative, blue line). Comparison of DFS (C) and OS (D) of patients carrying EGFR molecular alterations in LN (LN^{EGFR MT}, green line), RAS molecular alterations in LN (LN^{RAS MT}, yellow line), other molecular alterations in LN (LN^{Other MT} purple line) and patients without molecular alterations in LN (LN^Negative, blue line). Comparison of DFS (E) and OS (F) of EGFR-mutant patients with molecular alterations in LN (Lung^{EGFR MT}LN^{EGFR MT}, green line), EGFR-mutant patients without molecular alterations in LN (Lung^{EGFR MT}LN ^Negative, blue line), RAS-mutant patients with molecular alterations in LN (Lung^{RAS MT}LN^{RAS MT}, purple line), and RAS-mutant patients without molecular alterations in LN (Lung^{RAS MT}LN ^Negative, yellow line). p was determined with the log-rank test.