A 62-year-old woman with no smoking history presents with progressive dyspnoea and chest pain for 2 months. Imaging shows a 5.5 cm mass in the left lower lobe with pleural effusion. Pleural fluid analysis is positive for malignant cells. Bronchoscopy with biopsy confirms adenocarcinoma with EGFR exon 19 deletion mutation. CT brain and bone scan are negative. What is the most appropriate first-line treatment for this patient?

Explanation

## EGFR-Mutant NSCLC: First-Line Treatment Strategy **Key Point:** In NSCLC with activating EGFR mutations (exon 19 deletion or L858R), **EGFR tyrosine kinase inhibitors (TKIs)** are the standard of care for first-line therapy, not chemotherapy. ### EGFR Mutation Status and Treatment | EGFR Status | First-Line Recommendation | Rationale | |-------------|--------------------------|----------| | **Exon 19 deletion or L858R** | EGFR TKI (erlotinib, gefitinib, afatinib) | Superior PFS and ORR vs chemotherapy | | Uncommon mutations (G719X, L861Q, S768I) | EGFR TKI or chemotherapy | Variable TKI sensitivity | | Wild-type EGFR | Platinum-based chemotherapy ± bevacizumab | Standard doublet (cis/carbo + pemetrexed/gemcitabine) | | ALK-positive | ALK inhibitor (crizotinib, alectinib) | Superior to chemotherapy | | PD-L1 ≥50% (wild-type) | Pembrolizumab monotherapy | Improved OS vs chemotherapy | ### Case Analysis 1. **EGFR exon 19 deletion:** Activating mutation → **EGFR TKI is first-line** 2. **Stage:** T3 (5.5 cm) with pleural effusion = **Stage IIIB–IVA** (pleural involvement = M1a) 3. **No brain or bone metastases:** Systemic therapy appropriate **High-Yield:** EGFR exon 19 deletion and L858R mutations are **sensitizing mutations** that confer superior response to TKIs. Landmark trials (NEJM 2009, EURTAC 2012) demonstrated that first-generation TKIs (erlotinib, gefitinib) achieve median PFS of 9–13 months vs 5–6 months with chemotherapy. ### EGFR TKI Options | Drug | Selectivity | Median PFS (exon 19 del) | Toxicity Profile | |------|-------------|-------------------------|------------------| | **Erlotinib** | 1st-gen | 9.7 months | Rash, diarrhoea | | **Gefitinib** | 1st-gen | 10.8 months | Rash, diarrhoea | | **Afatinib** | 2nd-gen (irreversible) | 13.6 months | Diarrhoea, rash (more severe) | | **Dacomitinib** | 2nd-gen (irreversible) | 14.7 months | Diarrhoea, rash | **Clinical Pearl:** Although afatinib and dacomitinib show longer PFS, erlotinib and gefitinib remain widely used due to better tolerability. Second-generation TKIs are preferred in patients with diarrhoea-tolerant phenotypes or those requiring longer PFS. **Mnemonic: EGFR-TKI FIRST** — **F**irst-generation or second-generation TKI, **I**n EGFR-mutant NSCLC, **R**esponse superior to chemo, **S**ensitizing mutations (exon 19, L858R), **T**yrosine kinase inhibitor is standard of care.