Which of the following genetic alterations is most commonly associated with adenocarcinoma of the lung in never-smokers?

Question

Accepted Answer

A. EGFR mutation. ## EGFR Mutations in Lung Adenocarcinoma

**Key Point:** EGFR (Epidermal Growth Factor Receptor) mutations are the most frequent actionable mutations in adenocarcinoma, particularly in never-smokers, females, and East Asian populations.

### Epidemiology & Association
- **EGFR mutations** occur in 10–15% of Western lung adenocarcinomas but up to 30–50% in Asian populations
- Strongly associated with **never-smokers** (>40% of never-smoker adenocarcinomas harbour EGFR mutations)
- More common in **females** and **younger patients**
- Rare in squamous cell carcinoma and small cell lung cancer

### Clinical Significance
- **Predictive marker** for response to EGFR tyrosine kinase inhibitors (TKIs): erlotinib, gefitinib, afatinib
- Patients with EGFR mutations have **superior progression-free survival** with TKI monotherapy vs. chemotherapy
- Exon 19 deletions and exon 21 L858R point mutations account for ~90% of sensitizing mutations

### Contrast with Other Mutations

| Mutation | Frequency in Adenocarcinoma | Smoker Association | Clinical Implication |
|----------|----------------------------|-------------------|----------------------|
| **EGFR** | 10–15% (West), 30–50% (Asia) | Never-smokers | TKI-sensitive |
| **KRAS** | 25–30% | Smokers | Chemotherapy, emerging targeted agents |
| **TP53** | 50% | Smokers | Poor prognosis, not actionable |
| **ALK** | 3–5% | Never-smokers | ALK inhibitors (crizotinib, alectinib) |

**High-Yield:** EGFR mutation testing is **mandatory** in all adenocarcinomas, especially in never-smokers, to guide first-line TKI therapy.

**Clinical Pearl:** Presence of EGFR mutation is associated with **better initial response** to therapy but risk of acquired resistance via secondary mutations (e.g., T790M).

![Lung Cancer — Non-Small Cell diagram](https://mmcphlazjonnzmdysowq.supabase.co/storage/v1/object/public/blog-images/explanation/3718.webp)

Answer

B. RB1 deletion

Answer

C. TP53 mutation

Answer

D. KRAS mutation

Which of the following genetic alterations is most commonly associated with adenocarcinoma of the lung in never-smokers?

Explanation

EGFR Mutations in Lung Adenocarcinoma

Epidemiology & Association

Clinical Significance

Contrast with Other Mutations

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Mutation	Frequency in Adenocarcinoma	Smoker Association	Clinical Implication
EGFR	10–15% (West), 30–50% (Asia)	Never-smokers	TKI-sensitive
KRAS	25–30%	Smokers	Chemotherapy, emerging targeted agents
TP53	50%	Smokers	Poor prognosis, not actionable
ALK	3–5%	Never-smokers	ALK inhibitors (crizotinib, alectinib)