# Molecular Pathology of Advanced NSCLC: Biomarkers and Therapeutic Decisions

## TL;DR

This study shows that comprehensive genetic testing in advanced lung cancer helps identify key mutations like KRAS and EGFR, which influence treatment choices and patient outcomes.

## Contribution

The study confirms the importance of broad molecular profiling in NSCLC and highlights sex-specific and smoking-related biomarker patterns.

## Key findings

- KRAS mutations were most common (27%), with G12C being the largest subgroup.
- EGFR mutations occurred in 17% of cases, predominantly in never-smokers and women.
- TP53 mutations were frequent (~52%) and often acted as co-drivers without targeted therapy options.

## Abstract

Molecular diagnostics are central to NSCLC (Non-Small Cell Lung Cancer) management. Both the S3 guideline and the NCCN (National Comprehensive Cancer Network) recommend comprehensive NGS (Next-Generation Sequencing)-based profiling for all stage IV patients before therapy decisions. In addition to established biomarkers such as EGFR (epidermal growth factor receptor), ALK (anaplastic lymphoma kinase), KRAS (Kirsten rat sarcoma virus oncogene homologue), BRAF (B-Raf proto-oncogene serine/threonine kinase), MET (mesenchymal–epithelial transition factor), RET (rearranged during transfection), ROS1 (ROS proto-oncogene 1), NTRK (neurotrophic receptor tyrosine kinase), and HER2 (human epidermal growth factor receptor 2), emerging alterations such as FGFR (fibroblast growth factor receptor), NRG1 (neuregulin 1), and MET exon 14 skipping or amplification should be assessed. PD-L1 (programmed death-ligand 1) testing is mandatory to guide immunotherapy decisions. Our cohort of 48 samples confirms the relevance of these biomarkers: KRAS mutations were most common (27%, with G12C the largest subgroup), while EGFR mutations occurred in 17% of cases, predominantly in never-smokers and women. ALK and ROS1 fusions as well as NTRK alterations were not observed; rare occurrences included one BRAF V600E, one MET exon 14 mutation, and one RET mutation. TP53 (tumor protein p53) mutations were frequent (~52%), often as a co-driver without targeted therapy options. Patient-related factors such as smoking status, sex, and PD-L1 expression strongly influenced biomarker patterns and treatment considerations: never-smokers were enriched for EGFR and MET alterations, whereas smokers showed higher prevalence of KRAS; women exhibited higher rates of EGFR mutations and higher PD-L1 expression, which may contribute to sex-specific differences in immunotherapy response. STK11 [serine/threonine kinase 11] mutations clustered in PD-L1–negative tumors, supporting an immunosuppressive phenotype. Overall, the data align with guideline recommendations and underscore the importance of broad molecular profiling in NSCLC. Integrating genetic alterations with clinical features such as smoking history, sex, and PD-L1 status enables more precise patient stratification and personalized therapy.

Background: Advances in molecular pathology have transformed NSCLC (Non-Small Cell Lung Cancer) diagnosis, prognosis, and treatment by enabling precise tumor characterization and targeted therapeutic strategies. We review key genomic alterations in NSCLC, including EGFR (epidermal growth factor receptor) mutations, ALK (anaplastic lymphoma kinase) and ROS1 (ROS proto-oncogene 1) rearrangements, BRAF (B-Raf proto-oncogene serine/threonine kinase) mutations, MET (mesenchymal–epithelial transition factor) alterations, KRAS (Kirsten rat sarcoma) mutations, HER2 (human epidermal growth factor receptor 2) alterations and emerging NTRK (neurotrophic receptor tyrosine kinase) fusions and AXL-related pathways. Methods: A total of 48 patients with NSCLC was analyzed, including 22 women and 26 men (mean age 70 years, range 44–86). Tumor specimens were classified histologically as adenocarcinomas (n = 81%) or squamous cell carcinomas (n = 19%). Smoking history, PD-L1 (programmed death-ligand 1) expression, and genetic alterations were assessed. NGS (Next-generation sequencing) identified genomic variants, which were classified according to ACMG (American College of Medical Genetics and Genomics) guidelines. Results: The cohort consisted of 29 former smokers, 13 current smokers, and 5 non-smokers (12%), with a mean smoking burden of 33 pack years. PD-L1 TPS (tumor proportion score) was ≥50% in 10 patients, ≥1–<50% in 22, and <1% in 15 patients. In total, 120 genomic variants were detected (allele frequency ≥ 5%). Of these, 52 (43%) were classified as likely pathogenic or pathogenic, 48 (40%) as variants of unknown significance, and 20 (17%) as benign or likely benign. The most frequently altered genes were TP53 (tumor protein p53) (31%), KRAS and EGFR (15% each), and STK11 (serine/threonine kinase 11) (12%). Adenocarcinomas accounted for 89% of all alterations, with TP53 (21%) and KRAS (15%) being most common, while squamous cell carcinomas predominantly harbored TP53 (38%) and MET (15%) mutations. In patients with PD-L1 TPS ≥ 50%, KRAS mutations were enriched (50%), particularly KRAS G12C and G12D, with frequent co-occurrence of TP53 mutations (20%). No pathogenic EGFR mutations were detected in this subgroup. Conclusions: Comprehensive genomic profiling in NSCLC revealed a high prevalence of clinically relevant mutations, with TP53, KRAS and EGFR as the dominant drivers. The strong association of KRAS mutations with high PD-L1 expression, irrespective of smoking history, highlights the interplay between genetic and immunological pathways in NSCLC. These findings support the routine implementation of broad molecular testing to guide precision oncology approaches in both adenocarcinoma and squamous cell carcinoma patients.