Non-Small Cell Lung Cancer (NSCLC): Molecular Markers, Immune Therapy and Targeted Therapy

Background/Objectives: KRAS mutations are among the most common oncogenic driver alterations in non-small cell lung cancer (NSCLC) and define a biologically heterogeneous disease. In the current era of molecular oncology, with targeted therapies increasingly incorporated into clinical practice, the prognostic relevance of individual KRAS mutation subtypes and their relationship with immune biomarkers such as programmed cell death ligand 1 (PD-L1) require further clarification. This study aimed to evaluate the prognostic impact of KRAS mutation subtypes and their association with PD-L1 expression in patients with NSCLC. Methods: In this retrospective analysis, 150 patients with KRAS-mutant NSCLC who underwent next-generation sequencing at Trakya University Faculty of Medicine between January 2015 and December 2023 were included. Clinicopathological features, KRAS mutation subtypes, PD-L1 expression, and survival outcomes were assessed. Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan–Meier method, and prognostic factors were evaluated using Cox regression analyses. Results: KRAS G12C was the most frequent subtype (40.7%), followed by G12V (20.7%) and G12D (14.7%). OS differed significantly among KRAS mutation subtypes (log-rank p = 0.007), with median OS values of 18 months for G12D, 11 months for G12C, 11 months for other rare variants, 9 months for G12A and G12V, and 5 months for G13. PD-L1 positivity was significantly higher in KRAS G12C tumors compared with non-G12C subtypes and remained independently associated with improved OS in multivariate Cox regression analysis (HR = 0.622; 95% CI, 0.426–0.907; p = 0.014). In multivariate analysis, age, ECOG performance status, disease stage, and PD-L1 positivity were independent prognostic factors, whereas KRAS mutation subtype did not retain independent prognostic significance. Conclusions: These findings suggest that KRAS-mutant NSCLC represents a clinically and molecularly heterogeneous subgroup and that integrating KRAS mutation subtypes with immune biomarkers may support more refined prognostic stratification. Full article

Background and Objectives: Serum carcinoembryonic antigen (CEA) is a widely used biomarker in non-small cell lung cancer (NSCLC). However, its association with oncogenic driver alterations and prognostic significance across molecular subtypes in metastatic disease remains insufficiently defined. Materials and Methods: This retrospective multicenter study included 332 patients with metastatic NSCLC harboring oncogenic alterations (EGFR, ALK, ROS1, KRAS, and others) from eight oncology centers in Türkiye. Baseline serum CEA levels measured at metastatic diagnosis were analyzed on the natural logarithmic scale. Associations between CEA levels, molecular subtypes, clinical features, and overall survival (OS) were evaluated using generalized linear models and Cox proportional hazards regression. Results: Baseline CEA levels differed significantly across molecular subtypes (p = 0.001), with EGFR-mutant tumors showing the highest median levels. Multivariable analysis identified driver alteration, histology, and metastatic burden as independent determinants of baseline CEA. Higher baseline CEA and metastatic site count were independently associated with increased mortality risk (HR 1.151 and 1.279 per unit increase, respectively; p < 0.001), while female sex was protective (HR 0.626; p = 0.004). KRAS mutations were associated with poorer survival compared with EGFR (HR 2.370; p < 0.001). Kaplan–Meier analyses showed a consistent trend toward longer OS in patients with CEA < 5 ng/mL, with significance only in the rare alteration subgroup. Conclusions: Baseline CEA may reflect underlying tumor biology across molecular subtypes and are associated with survival outcomes in metastatic NSCLC. However, given the variability across subgroups and modest effect sizes, these findings should be interpreted with caution. Prospective studies evaluating longitudinal CEA dynamics are warranted. Full article

Background and Objectives: Non-small cell lung cancer (NSCLC) accounts for approximately 85% of all lung cancers and remains a leading cause of cancer-related mortality worldwide. EGFR-targeted tyrosine kinase inhibitors (TKIs) have substantially improved outcomes in EGFR-mutant NSCLC; however, primary and acquired resistance continues to limit their long-term efficacy. HER3 (receptor tyrosine-protein kinase ErbB3), a member of the ErbB receptor family, has been implicated in TKI resistance through heterodimerization with EGFR and HER2, leading to downstream PI3K/AKT pathway activation. Despite its biological plausibility as a resistance mediator, the clinical significance of HER3 expression as a prognostic and predictive biomarker in EGFR-mutant NSCLC has not been thoroughly characterized in real-world cohorts. Materials and Methods: This retrospective, single-center study included 52 patients diagnosed with EGFR-mutant NSCLC who received TKI therapy at Afyonkarahisar Health Sciences University between January 2011 and September 2023. HER3 protein expression was evaluated by immunohistochemistry (IHC) on formalin-fixed, paraffin-embedded tumor tissue sections using the Huabio anti-HER3 antibody (clone PD00-44, 1:2000 dilution). Staining in more than 30% of tumor cells was considered HER3-positive; membranous staining intensity was scored on a 1–3 scale. Progression-free survival (PFS1, PFS2) and overall survival (OS) were analyzed using the Kaplan–Meier method and log-rank test. Statistical significance was set at p < 0.05. Results: Of 52 patients (55.8% female; mean age 64.5 years), 59.6% received chemotherapy and 40.4% received an EGFR TKI as first-line treatment; erlotinib constituted 71.2% of targeted therapies. In the first-line TKI group, HER3-negative patients had a numerically longer median PFS1 compared with HER3-positive patients (14.0 vs. 7.1 months; p = 0.285); however, this difference did not reach statistical significance and should be interpreted with caution given the small sample size. In contrast, among patients receiving first-line chemotherapy, HER3 staining status did not meaningfully affect PFS1 (4.1 vs. 2.5 months; p = 0.063). In second-line treatment, HER3-positive patients who received TKI after prior chemotherapy demonstrated a PFS2 comparable to or slightly exceeding that of HER3-negative patients (21.8 vs. 19.8 months; p = 0.49), suggesting that the sequencing of chemotherapy before TKI may attenuate the adverse effect of HER3 positivity. Median OS was 15.1 months in HER3-negative patients and 12.7 months in HER3-positive patients (p = 0.824); this numerical difference of approximately 3 months did not reach statistical significance and should therefore be interpreted cautiously. Among patients receiving TKI in the first line, HER3-positive patients had a shorter median OS than HER3-negative patients (9.6 vs. 14.2 months), whereas those receiving TKI in the second line showed a trend toward longer OS in HER3-positive patients (20.5 vs. 17.2 months). Conclusions: HER3 expression was associated with reduced first-line TKI efficacy in EGFR-mutant NSCLC, suggesting a possible role for HER3 in primary TKI resistance; however, these findings are exploratory and did not reach statistical significance. The observation that HER3-positive patients who received chemotherapy before TKI demonstrated outcomes comparable to HER3-negative patients raises the hypothesis that treatment sequencing may potentially influence the impact of HER3 positivity, though this requires prospective validation before any clinical conclusions can be drawn. These results suggest that HER3 expression may warrant further investigation as a candidate biomarker for treatment sequencing decisions and as a potential therapeutic target in EGFR-mutant NSCLC. Prospective studies evaluating chemotherapy–TKI sequencing and HER3-directed agents such as patritumab deruxtecan (HER3-DXd) in HER3-positive patients are needed to confirm these preliminary observations. Full article