The landscape of biomarker testing in non-small cell lung cancer (NSCLC) is evolving significantly. Researchers are moving beyond traditional genomic drivers to include innovative protein-based and computationally derived markers. This shift, as outlined by Soo-Ryum (Stewart) Yang, MD, during his presentation at the 20th Annual New York Lung Cancers Symposium on November 15, 2025, is largely fueled by the approval of new therapies, particularly antibody-drug conjugates (ADCs), and a deeper understanding of therapeutic resistance.
In his presentation, Dr. Yang, who serves as an assistant attending pathologist and co-director of Clinical Biomarker Development at Memorial Sloan Kettering Cancer Center, highlighted four key trends reshaping NSCLC management. These include the increasing relevance of protein-based immunohistochemistry (IHC) biomarkers for ADCs, the actionability of tumor suppressor genes, advancements in synthetic lethality, and the burgeoning field of computational pathology.
Despite these advancements, a significant challenge remains: tissue scarcity. Dr. Yang emphasized the urgent need to develop and implement multiplex IHC and integrate broad panel next-generation sequencing (NGS) alongside artificial intelligence (AI) to provide personalized therapies to a larger segment of the NSCLC patient population.
Emerging Protein Biomarkers in NSCLC
Recent findings indicate that the expression levels of specific proteins on cancer cells are emerging as critical, actionable biomarkers. Instead of merely identifying mutated genes, pathologists are now focusing on measuring the intensity of protein expression, which can unlock new treatment options.
While the PD-L1 IHC test has been established to guide checkpoint inhibitor therapy, it is now being utilized to steer ADC usage. Dr. Yang identified two essential protein biomarkers for NSCLC: HER2 and c-MET overexpression. He noted that these biomarkers differ significantly from their genetic counterparts. HER2 overexpression occurs in up to 20% of patients, with the highest level (IHC 3+) found in approximately 3%. Notably, there is no correlation between HER2 mutation status and overexpression. Most NSCLC cases with high-level gene amplification will display IHC 3+ staining; however, not all 3+ cases are driven by amplification.
The FDA approved fam-trastuzumab deruxtecan-nxki (T-DXd; Enhertu) for HER2-positive (IHC 3+) solid tumors, which includes NSCLC patients who have undergone prior treatment. This decision was supported by the findings from the phase 2 DESTINY-Lung01 study (NCT03505710), which utilized scoring guidelines from gastric cancer that should now be applied to NSCLC testing.
c-MET overexpression is prevalent in NSCLC, with an actionable c-MET-high status, defined as over 50% of tumor cells showing 3+ staining, present in up to 17% of EGFR wild-type cases. Dr. Yang pointed out that c-MET overexpression can coexist with other driver mutations, distinguishing it from MET exon 14 skipping mutations and MET amplification. In May 2025, the FDA granted accelerated approval to telisotuzumab vedotin-tllv (teliso-V; Emrelis) for this patient demographic, supported by data from the phase 2 LUMINOSITY trial (NCT03539536).
Dr. Yang proposed that integrating HER2 and c-MET IHC screening could present significant challenges to current diagnostic workflows. He recommended a flexible approach, allowing institutions to optimize workflows based on their resources and multidisciplinary input.
Unraveling KRAS and Other Mutations
Several promising biomarkers are currently under investigation, with the potential to refine personalized treatment for NSCLC patients. KRAS mutations occur in up to 40% of lung adenocarcinomas, with mutations in codons G12, G13, and Q61. The KRAS G12C mutation is the most prevalent, followed by G12V and G12D mutations. Dr. Yang explained that KRAS G12D mutations correlate with a history of never or light smoking, a lower tumor mutational burden, and poorer responses to chemoimmunotherapy.
Targeted therapies for KRAS G12C, such as sotorasib (Lumakras) and adagrasib (Krazati), are already established and approved. Additionally, new targeted therapies beyond KRAS G12C-directed agents, including multi-RAS and RAS(ON) inhibitors, are undergoing clinical trials. Notably, zoldonrasib (RMC-9805), a KRAS G12D inhibitor, yielded an overall response rate of 61% in a phase 1 study (NCT06040541).
Furthermore, the multi-RAS inhibitor daraxonrasib (RMC-6236) has shown promise in treating KRAS G12V-mutant NSCLC and pancreatic cancer. Dr. Yang noted that KRAS mutations are easily detectable through existing NGS and PCR technologies, which do not present the same workflow challenges as IHC testing for HER2 and c-MET.
Another critical area of focus is the mutations in tumor suppressor genes such as STK11 and KEAP1, found in up to 20% of lung cancers and frequently co-mutated with KRAS. These mutations foster an immunosuppressive tumor microenvironment, leading to primary resistance to immunotherapy. Dr. Yang cited data from the phase 3 POSEIDON trial (NCT03164616), indicating that combining a CTLA-4 inhibitor with a PD-L1 inhibitor and chemotherapy improved progression-free survival and overall survival for these patients.
To detect the full range of inactivating mutations across STK11 and KEAP1, broad-panel NGS is essential, as PCR methods are inadequate.
Dr. Yang elaborated on the role of MTAP in the purine salvage pathway, noting that its deletion in cancer cells creates a metabolic vulnerability. MTAP deletions occur in up to 18% of lung cancers and are associated with poor outcomes, particularly in immunotherapy contexts. As such, MTAP is emerging as a therapeutic target, with encouraging clinical trial data for PRMT5 inhibitors in MTAP-deleted lung cancers.
Detection methods for MTAP include NGS, which identifies homozygous deletions, and IHC, which detects loss of MTAP protein expression. Dr. Yang proposed a diagnostic workflow involving NGS for initial screening, with confirmatory IHC for cases with retained or borderline MTAP status.
Although progress has been made, Dr. Yang cautioned that tissue availability continues to be a significant issue. As the number of biomarkers requiring testing expands, the demand for tissue samples will become more pressing.
Additionally, TROP2 is gaining attention as a promising target for ADC development. The anti-TROP2 ADC datopotamab deruxtecan-dlnk (Dato-DXd; Datroway) is currently being evaluated as a second-line treatment. The phase 3 TROPION-Lung01 study (NCT04656652) indicated a progression-free survival benefit with Dato-DXd over docetaxel, but did not show a statistically significant overall survival benefit.
To enhance predictive power, researchers developed an AI-driven method utilizing computational pathology to assess TROP2 expression. This involves scanning IHC slides and using an AI algorithm to measure staining intensity. When retrospectively applied to the TROPION-Lung01 study, a higher TROP2 quantitative continuous score was associated with improved response rates and longer progression-free survival.
Despite these promising findings, Dr. Yang raised concerns regarding the accessibility of this biomarker testing, as it is currently linked to a proprietary digital pathology ecosystem.
The advancements in lung cancer management are shifting towards a comprehensive approach that integrates protein analysis, AI insights, and novel therapeutic strategies. Dr. Yang concluded, “We’re at a point where we should be starting to explore the feasibility of multiplex IHC similar to what we did with molecular markers and NGS. In the next few years, broad-panel NGS and IHC, along with AI, are going to be the cornerstones of comprehensive biomarker testing in lung cancer.”
