Firmonertinib Combined With Definitive Radiotherapy in Stage III Unresectable EGFR Uncommon Mutant Pulmonary Adenocarcinoma

The standard treatment for patients with unresectable Stage III non-small cell lung cancer (NSCLC) is definitive concurrent chemoradiotherapy followed by consolidative immunotherapy with durvalumab. However, the efficacy of this approach remains limited. For EGFR-mutant patients, the benefit of immunotherapy is modest, highlighting the need for alternative strategies. Although the third-generation EGFR-TKI firmonertinib has become a standard first-line therapy for advanced NSCLC harboring common EGFR mutations (exon 19 deletions and L858R), patients with uncommon EGFR mutations (e.g., G719X, S768I, L861Q, and various exon 20 insertion mutations) represent a heterogeneous and understudied population. For most of these uncommon mutations, no approved targeted therapy currently exists in the setting of Stage III unresectable NSCLC. Firmonertinib is a novel, brain-penetrant third-generation EGFR-TKI that selectively and irreversibly inhibits both EGFR-sensitizing and T790M resistance mutations. It has demonstrated significant efficacy and a manageable safety profile in patients with EGFR T790M-mutant advanced NSCLC, and has also shown promising results in the first-line treatment of common EGFR mutations. Preclinical and clinical evidence suggests that combining EGFR-TKIs with radiotherapy may yield synergistic effects. Radiotherapy induces DNA damage and alters the tumor microenvironment, potentially enhancing both local and systemic efficacy of targeted agents. This combination strategy could be superior to sequential therapy or radiotherapy alone, particularly in molecularly selected populations. This study aims to explore the potential of this targeted-radiotherapy combination as a novel, chemotherapy-sparing, curative-intent treatment paradigm for patients with Stage III, EGFR uncommon mutation-positive lung adenocarcinoma. This is an exploratory, Phase II, single-arm study. Enrolled patients will receive the study intervention consisting of oral firmonertinib (160 mg once daily) administered continuously until disease progression, unacceptable toxicity, or other treatment discontinuation criteria are met, concurrently with definitive radiotherapy. Radiotherapy will be delivered using intensity-modulated radiotherapy (IMRT) or volumetric modulated arc therapy (VMAT) to a total dose of 60 Gy in 30 fractions over approximately 6 weeks, with strict adherence to standard organ-at-risk dose constraints and institutional quality-assurance protocols. The primary objective is to evaluate progression-free survival (PFS). Secondary objectives include overall survival (OS), objective response rate (ORR), disease control rate (DCR), safety, and exploratory analyses within specific mutation subgroups.