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Lung Cancer Risk Factors, Warning Signs, and Prevention Strategies

Lung cancer is the leading cause of cancer death worldwide. Understanding risk factors and recognizing symptoms early can save lives.

Major Risk Factors

  1. Smoking: #1 cause; ~80–90% of cases. Dose-dependent (pack-years). Cigarette smoke contains 70+ known carcinogens.
  2. Secondhand Smoke: Increases risk 20–30% in non-smokers.
  3. Radon Gas: #2 cause overall; #1 in never-smokers. Radioactive decay product of uranium in soil; accumulates in basements. Test homes; mitigate if ≥4 pCi/L.
  4. Occupational Carcinogens: Asbestos (synergistic with smoking), arsenic, chromium, nickel, silica, diesel exhaust, beryllium.
  5. Air Pollution: Outdoor PM2.5 (IARC Group 1); indoor biomass fuel combustion.
  6. Genetics/Family History: 2–3× risk with first-degree relative; GWAS identify susceptibility loci (e.g., 15q25, 5p15).
  7. Prior Lung Disease: COPD, pulmonary fibrosis, TB scarring increase risk independent of smoking.
  8. Age: Median diagnosis ~70 years; rare <40.

Red-Flag Symptoms (Often Late)

  • Persistent cough ≥3 weeks (or change in chronic cough).
  • Hemoptysis (coughing blood) – even streaks.
  • Chest pain worsened by breathing/coughing.
  • Dyspnea, wheezing, hoarseness (recurrent laryngeal nerve).
  • Unexplained weight loss, anorexia, fatigue.
  • Recurrent pneumonia/bronchitis in same lobe.
  • Superior vena cava syndrome (facial/arm swelling, distended neck veins).
  • Paraneoplastic syndromes (SIADH, Lambert-Eaton, hypertrophic osteoarthropathy).

Screening and Prevention

  • LDCT Screening: Annual low-dose CT for adults 50–80 with ≥20 pack-year history, current or quit <15 years (USPSTF Grade B). Reduces mortality 20%.
  • Smoking Cessation: Most impactful intervention; risk declines steadily after quitting.
  • Radon Testing/Mitigation: Simple, inexpensive.
  • Occupational Protection: PPE, ventilation, exposure monitoring.
  • Diet: High fruit/vegetable intake modestly protective (antioxidants).

Early-stage (I/II) lung cancer is potentially curable with surgery ± adjuvant therapy. Most cases present at stage III/IV. Vigilance and screening are critical.

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