Firmonertinib Versus Platinum Based Chemotherapy as First-line Treatment for NSCLC With EGFR PACC or EGFR l861q Mutation

Inclusion Criteria: 1. Voluntarily sign the informed consent form (ICF). 2. Age ≥18 years at the time of ICF signing. 3. At least one measurable lesion per RECIST v1.1, meeting the following: * No prior local therapy (e.g., radiotherapy) * Not used for biopsy during screening 4. Histologically/cytologically confirmed non-squamous NSCLC, classified as: * Locally advanced (Stage IIIB/IIIC, unsuitable for curative surgery and/or definitive chemoradiotherapy) * Metastatic (Stage IV) (Based on UICC/AJCC 8th edition TNM staging) 5. Agreement to provide: * Recent tumor tissue (from untreated lesions) * Blood samples * Central lab-confirmed EGFR PACC or L861Q mutation (If tumor tissue is unavailable due to inaccessible lesions, sponsor consultation is required.) 6. No prior systemic therapy for advanced/metastatic NSCLC. * Allowed if: Prior (neo)adjuvant/definitive chemoradiotherapy completed ≥12 months before recurrence/progression 7. ECOG performance status 0-1. 8. Life expectancy ≥12 weeks. 9. Adequate bone marrow/organ function within 14 days before treatment (no transfusion/G-CSF within 2 weeks prior). 10. Women of childbearing potential (WOCBP): * Abstinence or contraception use * No egg donation 11. Non-sterilized males: * Abstinence or contraception use * No sperm donation 12. CNS metastases allowed if protocol-specified criteria are met. Exclusion Criteria: 1. Histologically/cytologically confirmed tumor with \>10% neuroendocrine carcinoma, sarcomatoid carcinoma, or squamous cell components. 2. Known ALK-positive, ROS1-positive, RET fusion-positive, NTRK fusion-positive, BRAF V600E mutation, MET exon 14 skipping mutation, or other targetable alterations with approved therapies. 3. Prior treatments including: 1. Systemic anti-tumor therapy for advanced/metastatic NSCLC (e.g., chemotherapy/targeted/immunotherapy). Neoadjuvant/adjuvant therapy exceptions per Inclusion Criterion #6. 2. \>30 Gy thoracic radiotherapy within 6 months or non-thoracic radiotherapy within 4 weeks prior to first dose (brain radiotherapy exceptions per Inclusion Criterion #12). 3. Any prior EGFR-targeted therapy (including investigational EGFR-TKIs, mAbs, bispecific antibodies, etc.). 4. Strong CYP3A4 inhibitors within 7 days or inducers within 21 days prior to first dose. 5. Anticancer traditional Chinese medicines within 2 weeks prior to first dose. 6. Non-specific immunomodulators (e.g., interferon, IL-2, thymosin) within 2 weeks prior to first dose. 7. Major trauma/surgery within 4 weeks prior to treatment initiation. 4. Clinically significant gastrointestinal abnormalities, including: * Moderate/severe atrophic gastritis * GI obstruction/perforation * Chronic diarrhea/short bowel syndrome * Major upper GI surgery (e.g., gastrectomy) * Inflammatory bowel disease (Crohn's/ulcerative colitis) or active intestinal inflammation * Inability to swallow tablets 5. Uncontrolled systemic diseases. 6. Severe acute/chronic infections. 7. Interstitial lung disease (ILD)/non-infectious pneumonia: * History requiring clinical intervention * Current presence * Suspicious imaging findings unresolved at screening 8. Clinically significant cardiovascular dysfunction (active or history). 9. Tumor invasion of critical adjacent structures (heart/esophagus/SVC etc.) with high bleeding/fistula risk. Exceptions may be considered if investigator assesses minimal risk. 10. Pulmonary comorbidities causing severe impairment, including: 1. Baseline lung diseases (e.g., pulmonary embolism \[≤3 months\], severe asthma/COPD/restrictive disease) 2. Autoimmune/connective tissue disorders with pulmonary involvement (e.g., rheumatoid arthritis, sarcoidosis) 11. Residual toxicity \>Grade 1 (per NCI CTCAE v5.0) from prior anticancer therapy (except alopecia/neuropathy). 12. Concurrent malignancies except: * Cured localized skin cancers (BCC/SCC), superficial bladder cancer, cervical/breast DCIS, or papillary thyroid cancer * Other malignancies cured by radical therapy ≥3 years prior 13. Pregnancy/lactation or planned pregnancy within 6 months post-treatment. 14. Inability to comply with study procedures/follow-up. 15. Known hypersensitivity to furmonertinib or excipients. 16. History of allergic reactions to pemetrexed/cisplatin/carboplatin. 17. Other exclusionary per investigator judgment, including: * Alcohol/drug abuse * Severe comorbidities (including psychiatric) requiring treatment * Critical laboratory abnormalities * Social/familial factors compromising safety/data collection