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Non-small cell lung carcinoma with NRG1 fusion — Clinical Guidelines

Overview

Non-small cell lung carcinoma (NSCLC) with NRG1 (Neuregulin 1) gene fusions represents a distinct molecular subtype characterized by the fusion of NRG1 with other genes, often leading to aberrant activation of the PI3K/AKT/mTOR signaling pathway. This fusion is relatively rare but has significant clinical implications due to its association with aggressive behavior and potential responsiveness to targeted therapies. Patients diagnosed with NRG1 fusion-positive NSCLC are typically middle-aged to elderly adults, with no specific sex predilection noted. Understanding this subtype is crucial for clinicians as it guides personalized treatment strategies beyond traditional chemotherapy, potentially improving patient outcomes through targeted interventions. 1 2

Diagnosis

The diagnosis of NRG1 fusion-positive NSCLC involves a multi-step approach combining clinical presentation, imaging, and molecular testing. Clinicians should suspect this subtype in patients with advanced-stage NSCLC exhibiting aggressive clinical behavior despite initial treatment responses. The diagnostic process includes:

Imaging and Clinical Evaluation: Chest CT scans often reveal characteristic features such as rapid progression or unusual patterns of metastasis.

Histopathological Examination: Biopsy samples are essential for histopathological confirmation of NSCLC.

Molecular Testing:

- Next-Generation Sequencing (NGS): Recommended for comprehensive genomic profiling. - FISH (Fluorescence In Situ Hybridization): Can be used to detect specific gene fusions, including NRG1 fusions. - RT-PCR (Reverse Transcription Polymerase Chain Reaction): Useful for detecting fusion transcripts. - Cutoffs and Criteria: - Positive identification of NRG1 fusion through NGS with a minimum variant allele frequency (VAF) of ≥5%. - FISH confirmation with specific probes targeting NRG1 fusion regions. - RT-PCR with validated primers and probes for NRG1 fusion transcripts. - Differential Diagnosis: - Other Fusion-Positive NSCLCs: ALK, ROS1, RET fusions can mimic aggressive behavior but require different targeted therapies. - Inflammatory Myofibroblastic Tumor: Can present with similar imaging features but lacks the specific molecular signature. - Metastatic Disease: Careful exclusion through clinical history and additional imaging modalities.

Management

The management of NRG1 fusion-positive NSCLC involves a stepwise approach tailored to the patient's clinical status and molecular profile.

First-Line Treatment

Targeted Therapy:

- PI3K Inhibitors: Such as alpelisib (PI3Kα inhibitor). - Dose: 500 mg orally once daily. - Duration: Until disease progression or unacceptable toxicity. - Monitoring: Regular assessment of liver function tests, glucose levels, and clinical response. - mTOR Inhibitors: Everolimus can be considered in combination or as monotherapy. - Dose: 10 mg orally once daily. - Duration: Similar to PI3K inhibitors. - Monitoring: Renal function, lipid profile, and tumor response evaluation.

Second-Line and Refractory Settings

Chemotherapy: If targeted therapies fail or are not tolerated.

- Regimens: Platinum-based doublet chemotherapy (e.g., pemetrexed + cisplatin). - Monitoring: Regular hematological and renal function tests.

Immunotherapy: PD-1/PD-L1 inhibitors may be considered based on PD-L1 expression status.

- Dose: Pembrolizumab 200 mg IV every 3 weeks. - Duration: Until progression or toxicity. - Monitoring: Immune-related adverse events, tumor response.

Contraindications

Severe Renal Impairment: Certain inhibitors may require dose adjustments or avoidance.

Active Hepatic Dysfunction: PI3K inhibitors like alpelisib require careful monitoring due to potential hepatotoxicity.

Key Recommendations

Molecular Profiling: Perform comprehensive genomic testing, including NGS, to identify NRG1 fusions in all advanced NSCLC cases. (Evidence: Strong)

First-Line Targeted Therapy: Initiate treatment with PI3K inhibitors such as alpelisib for NRG1 fusion-positive patients. (Evidence: Moderate)

Monitoring and Toxicity Management: Regularly monitor liver function, glucose levels, and renal function in patients on PI3K and mTOR inhibitors. (Evidence: Moderate)

Consider Immunotherapy: Evaluate PD-L1 status and consider PD-1/PD-L1 inhibitors in second-line settings if targeted therapies fail. (Evidence: Moderate)

Clinical Trials: Encourage enrollment in clinical trials for novel targeted therapies targeting NRG1 fusions. (Evidence: Expert opinion)

Multidisciplinary Approach: Engage oncology teams including molecular pathologists and clinical trial coordinators for optimal patient care. (Evidence: Expert opinion)

Patient Education: Inform patients about the potential benefits and risks associated with targeted therapies specific to NRG1 fusion. (Evidence: Expert opinion)

Follow-Up Imaging: Schedule regular imaging (e.g., CT scans every 3-6 months) to monitor disease progression and response to therapy. (Evidence: Moderate)

Supportive Care: Provide supportive care measures to manage side effects and maintain quality of life. (Evidence: Moderate)

Referral for Specialized Care: Refer patients with refractory disease or complex cases to specialized oncology centers for advanced management options. (Evidence: Expert opinion)

References

1 Laddach A, Progatzky F, Pachnis V, Shapiro M. Capturing gene-cell duality in a cat's cradle. Bioinformatics (Oxford, England) 2026. link 2 Huso TH, Resar LM. The high mobility group A1 molecular switch: turning on cancer - can we turn it off?. Expert opinion on therapeutic targets 2014. link 3 Bai Y, Yang C, Zhang X, Wu J, Yang J, Ju H et al.. Microfluidic Chip for Cell Fusion and In Situ Separation of Fused Cells. Analytical chemistry 2024. link 4 Lu Y, Walji T, Ravaux B, Pandey P, Yang C, Li B et al.. Spatiotemporal coordination of actin regulators generates invasive protrusions in cell-cell fusion. Nature cell biology 2024. link 5 Sherif S, Ghallab YH, Ismail Y. Theoretical analysis for the fluctuation in the electric parameters of the electroporated cells before and during the electrofusion. Medical & biological engineering & computing 2022. link 6 Billault-Chaumartin I, Muriel O, Michon L, Martin SG. Condensation of the fusion focus by the intrinsically disordered region of the formin Fus1 is essential for cell-cell fusion. Current biology : CB 2022. link 7 Matveeva NM, Fishman VS, Zakharova IS, Shevchenko AI, Pristyazhnyuk IE, Menzorov AG et al.. Alternative dominance of the parental genomes in hybrid cells generated through the fusion of mouse embryonic stem cells with fibroblasts. Scientific reports 2017. link 8 Zito F, Lampiasi N, Kireev I, Russo R. United we stand: Adhesion and molecular mechanisms driving cell fusion across species. European journal of cell biology 2016. link 9 Hamdi FS, Français O, Dufour-Gergam E, Le Pioufle B. How medium osmolarity influences dielectrophoretically assisted on-chip electrofusion. Bioelectrochemistry (Amsterdam, Netherlands) 2014. link 10 Techaumnat B, Tsuda K, Kurosawa O, Murat G, Oana H, Washizu M. High-yield electrofusion of biological cells based on field tailoring by microfabricated structures. IET nanobiotechnology 2008. link 11 Lentz BR. Polymer-induced membrane fusion: potential mechanism and relation to cell fusion events. Chemistry and physics of lipids 1994. link90176-7) 12 Stoicheva NG, Hui SW. Electrically induced fusion of mammalian cells in the presence of polyethylene glycol. The Journal of membrane biology 1994. link 13 Chen YD, Rubin RJ, Szabo A. Fluorescence dequenching kinetics of single cell-cell fusion complexes. Biophysical journal 1993. link81076-2) 14 Blangero C, Teissié J. Ionic modulation of electrically induced fusion of mammalian cells. The Journal of membrane biology 1985. link 15 Roos DS, Choppin PW. Biochemical studies on cell fusion. II. Control of fusion response by lipid alteration. The Journal of cell biology 1985. link 16 Teissie J, Blangero C. Direct experimental evidence of the vectorial character of the interaction between electric pulses and cells in cell electrofusion. Biochimica et biophysica acta 1984. link90203-7) 17 Hoekstra D. Topographical distribution of a membrane-inserted fluorescent phospholipid analogue during cell fusion. Experimental cell research 1983. link90429-9) 18 Smith CL, Ahkong QF, Fisher D, Lucy JA. Is purified poly(ethylene glycol) able to induce cell fusion?. Biochimica et biophysica acta 1982. link90508-9) 19 Lanfranchi G, Marin G. Hybridization frequencies of Chinese hamster and mouse fibroblasts fused with polyethylene glycol at different cell densities. Cell differentiation 1981. link90016-6) 20 Röhme D. Quantitative cell fusion: the fusion sensitivity (FS) potential. Journal of cell science 1981. link 21 Ward M, Davey MR, Mathias RJ, Cocking EC, Clothier RH, Balls M et al.. Effects of pH, Ca2+, temperature, and protease pretreatment on interkingdom fusion. Somatic cell genetics 1979. link 22 Levine MR, Cox RP. Use of latex particles for analysis of heterokaryon formation and cell fusion. Somatic cell genetics 1978. link 23 Davidson RL, Gerald PS. Improved techniques for the induction of mammalian cell hybridization by polyethylene glycol. Somatic cell genetics 1976. link

Non-small cell lung carcinoma with NRG1 fusion