Evolution of lung adenocarcinoma from preneoplasia to invasive adenocarcinoma

OBJECTIVE

Mutations in driver genes contribute to the development and progression of lung adenocarcinoma (LUAD). However, in the dynamic evolutionary process from adenocarcinoma in situ (AIS) to minimally invasive adenocarcinoma (MIA) and eventually to invasive adenocarcinoma (IAC), the role of driver genes is currently unclear. This study aimed to analyse the role of driver gene status in the progression of LUAD from preneoplasia to IAC.

METHODS

Patients with LUAD who underwent surgery in our centre from March 2015 to December 2019 were retrospectively analysed, and LUAD patients with tumour sizes ≤3.0 cm and pN0 were included in the final analysis. The mutation status of common driver genes, including EGFR, ALK and ROS1, was detected. According to the pathological characteristics, the patients were divided into three stages: AIS, MIA and IAC. We analysed the distribution of driver gene mutation frequencies across three stages of LUAD. In addition, we performed univariate and multivariate analyses of IAC patients to screen for relevant variables (driver genes and clinicopathological features) affecting their prognosis.

RESULTS

Ultimately, 759 patients with LUAD were enrolled, including 135, 130, and 494 cases of AIS, MIA, and IAC, respectively. EGFR mutations were identified in 359 (61.8%) patients, and with the transition from AIS to MIA, the frequency of EGFR mutations increased from 33.3% to 50.8%, p = 0.004, whereas the frequency of EGFR mutations was comparable for MIA and IAC (50.8% vs. 50.2%, p = 0.922). Moreover, ALK and ROS1 gene fusions were identified in 17 cases (2.2%) and 2 cases (3.0‰) respectively. For AIS, neither ALK gene nor ROS1 gene fusions were observed. When the tumour progressed to MIA, the ALK fusion frequency was 2.3% (3/130), which was basically consistent with the ALK fusion frequency of 2.8% in IAC, p = 0.143. For IAC, fusions of ROS1 fell into this category. In addition, we found that 40 patients (5.3%) developed metastasis/recurrence, and 14 patients (1.8%) died of cancer-specific related diseases. Notably, for AIS, there were no recurrences and no deaths, and for MIA, only 1 patient died with LUAD. Finally, survival analysis was performed in patients with stage IA invasive adenocarcinoma, and EGFR-mutant patients showed better DFS than EGFR-wild-type patients (p = 0.036). Conversely, patients with ALK fusions showed worse DFS than those with ALK wild-type (p = 0.004), and the same results were found in OS analysis.

CONCLUSIONS

The accumulation of EGFR driver gene mutation frequencies mediates the progression of LUAD from AIS to MIA. When the tumour progresses to stage IA invasive adenocarcinoma, multivariate analysis based on driver gene status can be used as a pivotal prognostic factor.

Assessment of Nine Driver Gene Mutations in Surgically Resected Samples from Patients with Non-Small-Cell Lung Cancer

Background

The mutational profile of oncogenic driver genes play an important role in non-small-cell lung cancer (NSCLC). The need of a testing panel capable of comprehensively determining patient genotypes in limited amounts of material has increased since the recent association of nine core oncogenic driver genes as tumor predictive biomarkers.

Methods

Surgically resected samples from 214 NSCLC patients (168 patients with adenocarcinomas and 46 with squamous cell cancers) were included. A multiplexed PCR-based assay was developed to simultaneously test 118 hotspot mutations and fusions in nine driver genes.

Results

The sensitivity of the kit was 1% for gene mutation and 450 copies for gene fusion. Genetic alterations were detected in 143 (66.8%) patients by the assay. The three most common alterations identified were EGFR mutations (50.9%), KRAS mutations (8.4%) and ALK fusions (4.7%). Eight (3.7%) patients harbored concurrent mutations, and the most common partners were EGFR mutations which were observed in the eight patients. No associations between survival and EGFR, KRAS, and ALK status were observed. Patients with two or more alterations exhibited shorter DFS compared to those with single mutations (P=0.032), whilst had no significant difference in OS (P=0.245). However, only TNM stage was an independent predictor of OS (HR=2.905, P<0.001) as well as DFS (HR=2.114, P<0.001) in our cohort in multivariate analysis. Furthermore, patients with the L858R mutation had longer DFS (P=0.014) compared to other sensitizing mutations and tended to have better OS but the differences were not significant (P=0.06).

Conclusion

These findings suggest this multiplex gene panel testing technique can be efficiently used to detect nine driver genes in a limited number of specimens. This methodology would have the potential to save both specimens and time compared to the combination of all assays by other methods.