Search Results (239)

Background: Non-small cell lung cancer (NSCLC) remains the leading cause of cancer-related mortality despite major advances in diagnostics and therapies. The prognosis remains poor, mostly due to late-stage presentation and molecular heterogeneity. Epidermal growth factor receptor (EGFR) mutations are common drivers of NSCLC. The development of EGFR tyrosine kinase inhibitors (TKIs) has significantly improved outcomes in patients with EGFR mutations. Variant allele frequency (VAF) is a quantitative genomic measure representing the proportion of sequencing reads harboring a given mutation. In NSCLC tissue, the EGFR mutation VAF reflects tumor clonality and intratumoral heterogeneity, and accumulating evidence suggests an association between EGFR VAF and response to EGFR-targeted TKIs. Methods: To address the limited synthesis of data on the relevance of EGFR mutation VAF in NSCLC, we conducted a narrative review of the literature using PubMed/MEDLINE and Embase databases and current clinical guidelines, synthesizing available evidence on EGFR VAF, including its biological, molecular, and therapeutic implications in EGFR-mutated disease. The review was structured in accordance with the SANRA (Scale for the Assessment of Narrative Review Articles) checklist. Results: EGFR VAF and on-treatment VAF dynamics are consistently associated with treatment response, progression-free survival, and overall survival in osimertinib-treated NSCLC. Baseline VAF enables risk stratification, early clearance kinetics predict durable benefit, and longitudinal VAF monitoring facilitates early detection of resistance. Importantly, the prognostic implications of VAF differ fundamentally between tissue-based and plasma-based measurements: high tissue VAF reflects clonal homogeneity and predicts favorable TKI response, whereas high plasma VAF indicates elevated tumor burden and is associated with inferior outcomes. In the second-line setting, the T790M/activating mutation ratio serves as a surrogate for resistance clonality and independently predicts osimertinib efficacy. Conclusions: EGFR VAF represents a promising dynamic molecular biomarker for treatment monitoring and precision decision-making in EGFR-mutated NSCLC. Full article

Background: Acquired resistance to the third-generation EGFR tyrosine kinase inhibitor osimertinib, often mediated by EGFR triple mutations, poses a major clinical challenge in non-small cell lung cancer (NSCLC) treatment. Among these, some rare mutations, such as L858R/T790M/L792H and L858R/T790M/G796R, create steric hindrance that directly interferes with osimertinib binding, yet effective targeted therapeutic strategies for these specific mutations remain lacking. Cudratricusxanthone A (CTXA), a natural xanthone derivative isolated from Cudrania tricuspidata Bur., has demonstrated various pharmacological activities, but its effects against EGFR triple-mutant NSCLC have not been systematically investigated. Methods: Stable Ba/F3 and NIH/3T3 cell lines expressing EGFR L858R/T790M/L792H or L858R/T790M/G796R triple mutations were generated via electroporation. The antiproliferative effects of CTXA were evaluated by MTT/MTS assays, colony formation, and wound healing assays. Cell cycle distribution and apoptosis were analyzed by flow cytometry. Protein expression of EGFR signaling pathway components (p-EGFR, p-ERK, p-AKT, p-STAT3) and cell cycle regulators (Cyclin D1, CDK4) were examined by Western blotting. Molecular docking and 200 ns molecular dynamics simulations were performed to investigate the stability and binding modes of CTXA to the mutant EGFR kinase domains. Results: The successfully established triple-mutant cell lines exhibited high EGFR expression, IL-3-independent growth, and significant resistance to osimertinib. CTXA inhibited the proliferation of all triple-mutant cell lines in a time- and concentration-dependent manner, with 48 h IC₅₀ values ranging from 0.362 to 2.488 μM. Mechanistically, CTXA suppressed EGFR autophosphorylation and downregulated downstream p-ERK, p-AKT, and p-STAT3. CTXA induced G1 phase cell cycle arrest by downregulating Cyclin D1 and CDK4, significantly promoted apoptosis, and inhibited cell migration. Molecular docking revealed that while osimertinib binding was blocked by steric hindrance from His-792 or Arg-796, CTXA adapted to the mutated ATP-binding pockets through multiple hydrogen bonds and extensive hydrophobic interactions. Molecular dynamics simulations confirmed the stable binding of CTXA to both mutant EGFR proteins over the 200 ns simulations. Conclusions: This study demonstrates for the first time that the natural compound CTXA possesses antitumor efficacy against EGFR L858R/T790M/L792H and L858R/T790M/G796R mutants by regulating EGFR-ERK/AKT/STAT3 signaling. Our findings position CTXA as a promising lead compound for tackling this challenging form of acquired resistance and highlight the value of natural products in multi-target antitumor drug discovery. Full article

Background: The benefit of pharmaceutical innovation manifests when patients access treatment. Following regulatory approval in Europe and Canada, reimbursement decisions depend on health technology assessments (HTAs), which can be prolonged. To quantify the impact of delays on patients, we evaluated market access timelines for olaparib, osimertinib, durvalumab, acalabrutinib, and trastuzumab deruxtecan across six high-income countries with established HTA systems (Canada, England, France, Germany, Italy, Spain). Methods: Time to access was from regulatory approval to reimbursement. Survival benefit was median overall survival (OS) and progression-free survival (PFS) assessed versus the comparator at approval and the latest data cut-off. The number of eligible patients per year multiplied by the years to patient access and survival benefit reflects the lost survival benefit. Results: Efficacy benefits observed at approval continued to the latest data cut-offs. The mean time to patient access was 18 months. Although this varied by country and treatment, with England and Germany typically being the fastest and France and Spain the slowest, timelines often exceeded the 180-day EU target despite identical evidence used in HTA submissions. This resulted in an estimated mean of 2836 patients being unable to access treatment and 3391 OS-derived and 2739 PFS-derived life-years lost. Conclusions: Access processes must evolve to ensure the timely realization of new medicines’ benefits. Full article

Background: De novo (pretreatment) EGFR T790M mutation is a rare molecular finding in non-small cell lung cancer (NSCLC) and has historically been associated with primary resistance to first- and second-generation EGFR tyrosine kinase inhibitors (TKIs). Evidence guiding optimal first-line management in this subgroup, particularly in elderly patients, remains limited. Case Presentation: We report a case of an elderly patient with treatment-naïve advanced non-squamous NSCLC harboring a concurrent EGFR exon 19 deletion and de novo EGFR T790M mutation. Given the patient’s age, significant cardiopulmonary comorbidities, and absence of rapidly progressive disease, a multidisciplinary tumor board recommended first-line osimertinib monotherapy. Treatment was well tolerated, with rapid improvement in performance status and no clinically significant adverse events. Serial contrast-enhanced CT restaging demonstrated RECIST 1.1–defined stable disease, without development of new visceral, nodal, cerebral, or osseous metastases. The patient remains on continuous osimertinib therapy with durable disease control at the time of manuscript preparation. Conclusion: Primary EGFR T790M–positive NSCLC can achieve durable disease control with first-line osimertinib, even in advanced age. While combination strategies with chemotherapy may improve survival outcomes in selected patients, treatment decisions in elderly individuals must carefully balance efficacy, toxicity, and quality of life. Chronological age alone should not discourage active targeted treatment when guided by molecular profiling and comprehensive clinical assessment. Full article

Background: The introduction of targeted therapy in oncology has led to several challenges. These medicines are relatively new in clinical practice and are not well known to specialists with regard to adverse drug reactions (ADRs) and potential drug–drug interactions (pDDIs). In addition, cancer affects multiple body systems, including weight loss, anemia, liver and kidney function, depression, and pain. Patients frequently have comorbidities, leading to polypharmacy and the use of special foods, nutritional supplements, and herbal products for self-medication. Identification of pDDIs is essential, as concomitant use of multiple medicinal products increases the risk of ADRs and may compromise treatment. Objective: This study aims to retrospectively review and analyze data on ADRs and pDDIs in the treatment of non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) inhibitors and to evaluate the relationship between them. Method: EudraVigilance and UpToDate^® Lexidrug™ application were used to screen suspected ADRs and pDDIs, respectively. Descriptive statistical analysis was performed. Results: After reviewing Line Listing Reports (LLRs) from 2021 to 2023 in EudraVigilance, the number of suspected adverse drug reactions (ADRs) reported was higher when drug interactions classified as risk categories D and X were identified, compared with cases involving EGFR inhibitor monotherapy or other drug combinations. Of the 144 cases involving category D and/or X interactions, 63 demonstrated a possible association with the reported ADRs of EGFR inhibitors. The most common pDDIs detected were erlotinib–ranitidine (14 cases, category D) and osimertinib–amiodarone (13 cases, category D). Conclusions: Although EGFR inhibitors improve overall and progression-free survival in NSCLC, screening for pDDIs before treatment is essential to improve safety and quality of life. Full article

Background and Objectives: Combining osimertinib (OSI) with pemetrexed (PEM) can enhance antitumor efficacy; however, the benefit is schedule-dependent. Our previous pharmacodynamic (PD) study showed that concurrent PEM + OSI is limited by OSI-induced G1 arrest, attenuating early PEM cytotoxicity. In contrast, sequential PEM→OSI allows PEM to fully induce S-phase arrest and DNA damage but elicits a pro-survival EGFR rebound; subsequent OSI suppresses this rebound and promotes apoptosis of damaged cells, yielding strong synergy. Here, we investigated whether pharmacokinetic (PK) drug–drug interactions (DDIs) contribute to this synergy and predicted the relative advantage of PEM→OSI versus PEM + OSI under clinically relevant conditions using a PK/PD approach. Method and Results: Potential PK-DDIs were assessed at cellular uptake, plasma exposure, and intratumoral distribution levels. No meaningful PK-DDIs were observed, supporting a primary PD-driven synergy. We integrated mouse PK with in vitro/in vivo PD data to build a mechanistic Quantitative System Pharmacology (QSP)–PK–PD model linking drug disposition to folate biology, Epidermal Growth Factor Receptor (EGFR) signaling, and tumor growth inhibition. The model recapitulated schedule dependence and explained PEM→OSI superiority: PEM initiates damage and EGFR compensatory rebound, after which OSI suppresses EGFR signaling and enhances apoptosis. In contrast, concurrent PEM + OSI induced G1 arrest, reduced the pool of damaged apoptosis-susceptible cells, and weakened the synergy. Global sensitivity analysis identified intrinsic OSI sensitivity and the pro-apoptotic protein Bim as key determinants; reduced OSI sensitivity or Bim activity diminished the advantage of the sequential strategy. The simulations indicated that OSI can start 48 h after PEM exposure (no extended drug holiday is needed) and that the PEM→OSI benefit remains robust across heterogeneity, including BIM-deletion polymorphisms and inter-individual variability in tumor drug sensitivity. Conclusions: This mechanism-based QSP–PK–PD framework connects whole-body PK to core PD processes, explains schedule-dependent synergy, and supports optimization of sequencing intervals and identification of likely responders. Full article

Background: Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are the first-line treatment for patients with non-small cell lung cancer (NSCLC) harboring EGFR mutations. Although EGFR-TKIs can cause various adverse events (AEs), their profiles have not been fully elucidated in Thai patients. This study aimed to determine the incidence, characteristics, severity, and duration of the first AEs and to evaluate their association with tumor response in patients with NSCLC receiving EGFR-TKIs. Method: This retrospective cohort study was conducted at a super-tertiary care hospital in Thailand. Patients with NSCLC who received EGFR-TKIs between August 2021 and July 2024 were included. Descriptive statistics were used to summarize safety profiles and tumor response. The association between AEs and objective response was assessed using logistic regression. Results: A total of 187 patients were included in this study. Overall, 177 AEs were observed in patients receiving erlotinib, osimertinib, or gefitinib. The most common cutaneous AEs were rash (30.7%), xerosis (24.1%), and acneiform rash (19.3%), while diarrhea (20.3%) was the most frequent gastrointestinal toxicity. Most AEs were grade 1–2 and occurred within 1 month after treatment initiation. In multivariable logistic regression analysis, pruritus (OR 8.26, 95% CI: 1.00–67.75, p = 0.049) and treatment line (OR 0.27, 95% CI: 0.10–0.68, p = 0.006) were independently associated with objective response. Conclusion: Most of the AEs occurred early during EGFR-TKI therapy, with cutaneous reactions being the most common and generally mild to moderate. Pruritus and treatment line were independently associated with objective response, suggesting that pruritus may serve as a potential clinical indicator of treatment response and highlighting the importance of monitoring of the EGFR-TKI-related AEs during therapy. Full article

Non-small cell lung cancer (NSCLC) is the leading cause of lung cancer deaths, with resistance to targeted therapies posing a major clinical challenge. Drug-tolerant persister (DTP) cells are key contributors to resistance, and targeting them offers new strategies to enhance existing treatments. MicroRNAs (miRNAs), particularly the tumour-suppressive miR-15/107 family, offer promise due to their ability to target multiple oncogenic pathways. This study evaluated a synthetic consensus miRNA mimic, conmiR-15/107, in NSCLC cell line models. Dose–response assays showed robust, dose-dependent growth inhibition in both EGFR-mutant (PC9) and KRAS-mutant (H358 and A549) lung adenocarcinoma cells, but not in the human bronchial epithelial cell line BEAS-2B. When combined with EGFR inhibitors (osimertinib and gefitinib) in PC9 cells, the mimics showed a higher rate of growth inhibition compared with the controls and reduced IC₅₀ values. Similarly, conmiR-15/107 enhanced growth inhibition by the KRAS inhibitors sotorasib and adagrasib in H358 cells. RT-qPCR confirmed downregulation of conmiR-15/107 targets, including MEK1, BCL2 and BRCA1, suggesting a multi-target mechanism of action. Long-term assays showed that the mimics reduced the survival and delayed the proliferation of DTPs in osimertinib-treated PC9 cells as well as sotorasib-treated H358 cells. These findings support conmiR-15/107 as a potential adjunct to targeted therapy, capable of enhancing treatment efficacy and delaying resistance in lung adenocarcinoma. Full article

Background. NOTCH receptors play a pivotal role in carcinogenesis. Upon ligand binding, a cascade of proteolytic cleavages mediated by ADAM proteases and the γ-secretase complex activates the receptor, ultimately releasing the NOTCH intracellular domain (NICD). NICD translocates to the nucleus, where it regulates gene expression. This review mainly aims to evaluate γ-secretase inhibitors (GSIs) as anticancer agents in preclinical and clinical settings, with a focus on their ability to block tumor progression, target cancer stem cells, and overcome resistance to standard therapies. Methods. A systematic search was conducted in the ISI Web of Science, PubMed, and Scopus databases, following PRISMA guidelines. The review included preclinical in vitro and in vivo studies, as well as clinical trials, investigating GSIs, either as monotherapy or in combination with other treatments, in TNBC, metastatic melanoma, PDAC, gastric cancer, and NSCLC. Exclusion criteria included duplicates, non-English articles, studies published before 2010, studies on non-cancer conditions, research unrelated to NOTCH signaling, and studies outside the selected cancer types. Overall, 69 articles were included and categorized into the five types of cancer analyzed (20 on NSCLC, 22 on TNBC, 11 on metastatic melanoma, 7 on GC, and 9 on PDAC). Of these, 60 studies corresponded to preclinical research in the types of cancer, and 9 studies corresponded to clinical trials in the types of cancer except for GC. Two independent authors screened and extracted relevant data, with disagreements resolved by the corresponding author. Findings were synthesized qualitatively across cancer types under study. Results. This review summarizes therapeutic advances involving GSIs in cancers driven by oncogenic NOTCH signaling, based on the 69 articles included. Preclinical studies show that GSIs synergize with chemotherapy and radiotherapy, particularly in NSCLC, melanoma, and TNBC, and block EMT, overcome therapeutic resistance, and improve prognosis. Commonly used GSIs include DAPT and RO4929097, which enhance the efficacy of agents, such as gemcitabine (PDAC), paclitaxel, osimertinib, erlotinib, and crizotinib (NSCLC), and 5-FU (gastric cancer, TNBC). Promising strategies include combining GSIs with SAHA, ATRA, CB-103, and other NOTCH signaling targeting molecules, either alone or with chemo- and radiotherapy. Clinical trials with GSIs, however, remain limited. RO4929097 is the most extensively tested GSI in clinical settings. PDAC trials combining GSIs with gemcitabine showed no benefit; melanoma trials yielded modest outcomes; and TNBC trials demonstrated partial responses to GSIs but overall low efficacy and significant adverse events. Discussion and Conclusions. Despite encouraging preclinical evidence, clinical trials with GSIs have underperformed, largely due to tumor heterogeneity, dosing limitations, and the non-selective nature of γ-secretase inhibition. Other NOTCH inhibitors, such as DLL4 antibodies, also resulted in partial responses and secondary effects. Future strategies should prioritize receptor-specific NOTCH inhibitors, patient stratification based on NOTCH pathway activation, and optimized combination regimens. Emerging approaches include integrating immunotherapy with advanced technologies such as CRISPR, CAR-T cells, and bispecific antibodies, as well as targeted delivery systems to enhance efficacy and reduce toxicity. Additional research directions include addressing the tumor microenvironment and EMT-driven resistance, elucidating the mechanisms of immune evasion, and inhibiting tumor angiogenesis. Finally, leveraging artificial intelligence and big-data-driven personalized medicine, including sex-specific considerations, will be essential for improving patient outcomes. Full article

Targeted therapies have revolutionized treatment paradigms for a variety of cancer types; however, challenges including primary and acquired resistance persist, and there remains a high demand for novel treatment options. HER3 (ErbB3), a member of the human epidermal growth factor receptor family of receptor tyrosine kinases, is a target of HER3-DXd, an antibody–drug conjugate currently under clinical investigation. As was previously reported, the cytotoxic activity of HER3-DXd in preclinical models is primarily mediated by the antitumor activity of the released payload. Therefore, we investigated the impact of HER3 expression changes on payload release after HER3-DXd treatment using HER3-positive human cancer cell lines and their xenograft models. In vitro studies showed that the amount of payload released from cells after HER3-DXd treatment was associated with baseline HER3 expression levels, HER3 internalization rate, and turnover rate. In female CAnN.Cg-Foxn1nu/CrlCrlj mouse models, dose and dosing interval influenced membrane HER3 expression levels and tumor payload concentrations. Furthermore, membrane HER3 was upregulated by tyrosine kinase inhibitor treatment in non-small-cell lung cancer cell lines harboring specific driver mutations, including EGFR-activating mutations, ROS1 fusions, and ALK fusions. The increase in HER3 expression induced by osimertinib treatment was associated with increased payload release in PC-9 cells. Our results indicate that HER3 dynamics, as well as baseline HER3 expression, modulate payload release from HER3-DXd and support combination strategies to potentiate the antitumor activity of HER3-DXd. Full article

Surgical resection remains the cornerstone of curative-intent treatment for both oncogene and non-oncogene addicted early-stage non-small cell lung cancer, with neoadjuvant/adjuvant chemotherapy providing only a modest benefit in terms of disease-free survival and overall survival. Currently, in non-small-cell lung cancer without actionable molecular alterations, the addition of neoadjuvant or perioperative immunotherapy to chemotherapy has become the standard of care for resectable disease, with significant improvements in the rates of complete pathological response, major pathological response, and event-free survival. In terms of oncogene-addicted non-small-cell lung cancer, adjuvant treatment of completely resected disease with the third-generation EGFR inhibitor osimertinib in patients harboring activating EGFR mutations or the second-generation ALK inhibitor alectinib in patients with an ALK fusion/translocation has brought about a paradigm shift by significantly improving event-free survival and, in the case of osimertinib, overall survival. A glimpse into the future management of patients with early-stage disease and a common EGFR mutation or an ALK fusion/translocation may reveal a perioperative use of the respective targeted treatment. Data for the rest of the actionable molecular alterations remain limited, and those tumors are usually treated with algorithms used for non-oncogene-addicted non-small-cell lung cancer. This review aims to summarize all existing evidence about the current management of patients with early-stage non-small-cell lung cancer and actionable molecular alterations and to examine the future directions in this rapidly evolving field. Full article

Background: Epidermal growth factor receptor (EGFR) is a transmembrane tyrosine kinase that is frequently post-translationally modified by glycosylation. In cancer, EGFR amplifications and hotspot mutations such as L858R that promote proliferation have been detected in a significant fraction of non-small cell lung carcinomas and breast adenocarcinomas. Analyses of disruptions to glycosylation pathways in cancer cells identified EGFR glycosylation at residue N361 as one of the most heavily impacted sites. Methods: We stably expressed a glycosylation-deficient mutant EGFR, N361A, with or without the oncogenic EGFR mutation L858R in cells. Proximity ligation assays were employed to study the effects of the glycosylation mutant on the co-localization of EGFR and HER2. The effects of the glycosylation-deficient mutant on the efficacy of agonists, such as EGF and amphiregulin, or antagonists, such as osimertinib and necitumumab, were defined using cell viability assays and immunoblots. Results: N361A increased the membrane localization and co-localization of EGFR with its binding partner HER2. The glycosylation-deficient mutation decreased cell proliferation, including proliferative responses to EGFR ligands. The mutant cells demonstrated reduced sensitivity to inhibition using the antibody inhibitor necitumumab, which inhibits EGFR by binding the extracellular domain. Conclusions: Disruption of glycosylation at N361, located near the ligand binding and dimerization regions, created a dominant negative form of EGFR, which non-productively co-localized with HER2, resulting in a blockage in proliferation. These findings underline the critical relevance of post-translational glycosylation modifications on EGFR function. Full article

Background: Several studies evaluated the role of variant allele frequency (VAF) as a clinical decision-making tool for targeted therapies. However, its predictive role for treatment response in epidermal growth factor receptor (EGFR)-mutated non-small cell lung cancer (NSCLC) remains debated. This study investigates the relationship between VAF and early tumor shrinkage (ETS) and deepness of response (DpR). We also explored the impact of previously undescribed compound uncommon EGFR mutations on osimertinib activity. Methods: We retrospectively analyzed data from patients with advanced EGFR-mutated NSCLC, treated with osimertinib. VAF was obtained through NGS. We calculated corrected VAF (cVAF) based on the percentage of tumor cells. ETS and DpR were assessed according to RECIST 1.1 criteria. Molecular modeling was performed to predict the impact of novel compound EGFR mutations on osimertinib binding and EGFR protein structure. Results: We included 16 patients, who met the eligibility criteria. We found no significant correlation between cVAF and ETS or DpR, suggesting that cVAF may not have a direct effect on early or late tumor response to osimertinib. Median cVAF was 14%. Median progression-free survival and overall survival were longer in patients with higher VAF, even though they were not statistically significant. We identified two previously unreported compound EGFR mutations: N771Y + L858R and L718V + K713R + L858R. Conclusions: This study demonstrates that cVAF of EGFR mutations is not significantly associated with ETS or DpR during osimertinib in mNSCLC patients. Survival does not appear to be influenced by cVAF either. The identification and structural characterization of novel compound EGFR uncommon mutations may explain the benefit experienced by patients. Full article

Background/Objective: Osimertinib (OSI) is a third-generation tyrosine kinase inhibitor approved for non-small cell lung cancer (NSCLC) therapy. OSI is administered orally; this route limits the amount of OSI reaching the tumor in the lungs and is associated with serious systemic toxicity. This study aimed to develop a dry powder inhalable formulation to provide tumor-targeted delivery and minimize systemic toxicity. To the best of our knowledge, this is the first study to prepare and evaluate a dry powder inhalation formulation of OSI. Methods: Chitosan-coated PLGA nanoparticles (PLGA-C NPs) encapsulating OSI were prepared using a single emulsion-solvent evaporation technique. PLGA-C NPs were assembled into respirable nanocomposite microparticles (NCMPs) via spray drying with L-leucine as a carrier. PLGA-C NPs were characterized for particle size, zeta-potential, encapsulation efficiency, and in vitro efficacy in A-549 cell line. NCMPs were evaluated for solid-state properties, aerosolization performance, stability and in vitro release. Results: PLGA-C NPs exhibited a particle size of 145.18 ± 3.0 nm, high encapsulation efficiency and a positive zeta potential. In vitro studies demonstrated a 3.6-fold reduction in IC50 compared to free OSI, superior antimigratory effects and enhanced cell cycle arrest. Solid-state characterization of NCMPs demonstrated drug encapsulation in the polymer without chemical interaction. NCMPs exhibited excellent aerosolization (mass median aerodynamic diameter of 1.09 ± 0.23 μm, fine particle fraction of 73.48 ± 8.6%) and sustained drug release (61.76 ± 3.9% at 24 h). Stability studies confirmed the physicochemical stability integrity. Conclusions: These findings suggest that this novel dry powder inhalable OSI formulation may improve therapeutic outcomes while reducing systemic toxicity. Full article

Non-small cell lung cancer (NSCLC) accounts for approximately 85% of lung cancers with adenocarcinoma being the most common subtype. Patients with stage IV NSCLC typically have poor prognosis. In these patients, identification of actionable genomic alterations allows for the selection of targeted therapy rather than chemotherapy or chemo-immunotherapy. EGFR mutations are a common oncogenic driver in NSCLC and are targetable by tyrosine kinase inhibitors (TKIs). However, most of the studies primarily focus on common mutations, which are exon 19 deletions (Ex19del) and exon 21 (L858R) point mutations, and there is inconsistent data on efficacy in the treatment of patients with uncommon EGFR mutations. Currently, the first-line treatment for patients with common EGFR mutations involves a third-generation TKI, typically osimertinib. This case describes a 66-year-old gentleman with two uncommon EGFR frameshift deletions (E701fs and L702fs). His tumor staging was denoted as cT3N2M1b, stage IVA. The patient demonstrated a radiological and biochemical response to osimertinib as part of the OCELOT clinical trial (supported by a grant from AstraZeneca), with evidence of tumor marker decline and radiographic improvement within two months of osimertinib treatment initiation. This response has been durable with continued radiological stability and biochemical improvement at 11 months and ongoing. This case will help guide management for patients with this uncommon EGFR mutations and contribute to the scarce literature of EGFR frameshift deletions in advanced NSCLC patients. Full article