Molecular characterisation of KRAS mutations in non-small cell lung cancer across all stages

Abstract

Introduction: Kirsten rat sarcoma virus (KRAS) mutations (KRASms) are detected in approximately 25% of non-small cell lung cancer (NSCLC) patients with adenocarcinoma. Next-generation sequencing (NGS) has enabled the identification of diverse KRASm subtypes with distinct prognoses, co-mutation patterns and clinical characteristics. This study aimed to investigate the clinical and pathological characteristics of KRASm patients across all stages of NSCLC.

Methods: We analysed NSCLC patients from 2019 to 2021 using the Illumina Focus 52-gene targeted NGS panel, which detects DNA and RNA alterations. PD-L1 expression was assessed using the SP263 antibody. We examined the clinical and pathological characteristics of KRASm patients, including KRASm subtypes and co-mutations.

Results: Of the 123 patients, 62 (50.4%) had KRASm, with a median age of 67 years (range 49-92). Of these, 79% were male, 87.1% had adenocarcinomas and only 8.1% were non-smokers. NGS alone was sufficient for molecular characterisation in 19.4% of cases; in 75.8%, an additional single molecular test was required. KRASm subtypes were distributed as follows: G12C (33.8%), G12V (25.8%), G12D (21%) and Q61H (6.5%). G12V was more prevalent in non-smokers (60%). Co-mutations were detected in 24.2% of patients, with PIK3CA being the most frequent. PD-L1 expression >50% was observed in 19.4% of patients. No significant associations were identified between KRAS subtypes and PD-L1 expression levels or co-mutations.Significant differences in the clinical stage were noted across KRASm subtypes. Early-stage disease accounted for 24.19% of KRASm cases, with G12D observed in 40% of these patients. However, G12C and G12V subtypes were more frequently associated with metastatic disease (p = 0.004). While differences in median overall survival were observed across KRASm subtypes, they were not statistically significant (p = 0.5). The presence of co-mutations and high PD-L1 expression was suggested to be associated with a worse prognosis, without reaching statistical significance (p = 0.4 and p = 0.06, respectively).

Conclusion: This study underscores the importance of assessing KRAS status and subtypes in NSCLC, particularly in early-stage disease, due to their association with metastatic risk. This could have relevance in treatment strategies and subsequent monitoring, which could necessarily be closer in higher risk patients. Moreover, while PD-L1 status shows potential as a prognostic factor in KRASm patients, further research is needed to confirm this relationship.

Keywords: KRAS mutation; PD-L1; co-mutations; non-small cell lung cancer.

Figure 1.. Patients flowchart. Of the 123 patients, 62 had mutations in the KRAS oncogene and were selected as the final cohort.

Figure 2.. KRAS subtypes. In our cohort of 62 lung cancer patients with KRAS mutations, the most frequent subtype was G12C (33.8%), followed by G12V (25.8%), G12D (21%) and Q61H (6.5%). Eight patients (12.8%) had other KRAS mutation subtypes.

Figure 3.. (a–d): Relationship between KRAS mutation subtype and clinical stage, presence of metástasis, PD-L1 expression and presence of co-mutations. A statistically significant relationship was identified between the different clinical stages and the KRAS subtyes, with the KRAS G12D subtype being more frequent in patients with early-stage disease (p = 0.04) (a). In the same way, the KRAS subtype was related to the presence of metástasis, presenting a higher incidence of metastasis in those patients with KRAS G12C and G12V subtype mutations (p = 0.004) (b). On the contrary, the KRAS subtype was not significantly related to the percentage of PD-L1 expression (p = 0.16) (c) nor to the presence or absence of co-mutations (p = 0.26) (d).

Figure 4.. (a–c): Relationship between KRAS mutation subtype, PD-L1 expression or presence of co-mutations and overall survival. There were no significant differences in overall survival based on the KRAS mutation subtype (p = 0.6) (a) and co-mutations (p = 0.6) (b). In terms of PD-L1 expression, although statistical significance was not reached, patients with negative PD-L1 expression tended to have greater survival than those with PD-L1 expression >50% (p = 0.068) (c).