What is the value of spirometry in lung cancer and which measurements are necessary?

The Role of Spirometry in Lung Cancer Management

Spirometry is essential in lung cancer management for assessing surgical candidacy, predicting postoperative outcomes, and monitoring treatment response, with FEV1 and DLCO being the most critical measurements required.

Preoperative Assessment for Surgical Candidates

Key Spirometric Measurements

• Forced Expiratory Volume in 1 second (FEV1): Primary measure of airflow 1
• Diffusing Capacity for Carbon Monoxide (DLCO): Critical for assessing gas exchange 1
• Predicted Postoperative (PPO) values: Both PPO FEV1 and PPO DLCO must be calculated 1

Decision Algorithm for Surgical Risk Assessment

1. Initial Assessment:

   • Measure FEV1 and DLCO
   • Calculate predicted postoperative values (PPO FEV1 and PPO DLCO)

2. Risk Stratification:

   • Low Risk: If both PPO FEV1 and PPO DLCO ≥60% predicted → proceed to surgery 1
   • Intermediate Risk: If either PPO FEV1 or PPO DLCO between 30-60% predicted → perform exercise testing 1
   • High Risk: If either PPO FEV1 or PPO DLCO <30% predicted → perform cardiopulmonary exercise testing 1

3. Exercise Testing for Intermediate Risk:

   • Stair climbing test: ≥22 meters indicates low risk
   • Shuttle walk test: ≥400 meters indicates low risk 1

4. Cardiopulmonary Exercise Testing for High Risk:

   • Peak oxygen consumption (VO₂peak):
     • <10 mL/kg/min or <35% predicted: high risk

     • 20 mL/kg/min or >75% predicted: low risk 1

Calculation of Postoperative Lung Function

For pneumonectomy:

• PPO FEV1 = preoperative FEV1 × (1 - fraction of total perfusion in lung to be resected) 1

For lobectomy:

• PPO FEV1 = preoperative FEV1 × [(19 - a) - b]/(19 - a)
  • Where a = number of obstructed segments
  • b = number of functioning segments to be removed 1

Value Beyond Surgical Assessment

Prognostic Value

• Lower FEV1 and FVC values at diagnosis correlate with worse overall survival in NSCLC patients 2
• Patients with COPD (FEV1/FVC <0.7) or PRISm (FEV1/FVC ≥0.7 and FEV1% predicted <80%) have:
  • 2-4 fold increased risk of mortality
  • Higher risk of lung cancer
  • More advanced tumor stage at diagnosis 3

Treatment Response Monitoring

• Improvement in FEV1 and FVC correlates with tumor response after chemotherapy 4
• Changes in FEV1 show significant correlation with changes in tumor size (RECIST score) 4

Regional Function Assessment

• Regional ventilation and perfusion studies can help determine:
  • Proximity of tumor to hilum
  • Extent of safe resection
  • Need for pneumonectomy vs. lobectomy 5

Common Pitfalls and Caveats

1. Lobar Volume Reduction Effect: Patients with COPD may show minimal loss or even improvement in lung function after lobectomy when the most affected parenchyma is removed 1

2. Underestimation of Postoperative Function: Calculated PPO values tend to be conservative (underestimate) actual postoperative values, especially in patients with poor baseline function 1

3. Spirometry Alone Is Insufficient: While essential, spirometry should be part of a comprehensive assessment including:

   • Cardiovascular evaluation
   • Exercise capacity testing
   • Assessment of comorbidities 1

4. Age Is Not a Contraindication: Elderly patients should receive full evaluation regardless of age 1

5. Thoracoscopic Approaches: Modern surgical techniques like VATS may be better tolerated than traditional thoracotomy, but preoperative assessment criteria remain similar 1

Spirometry provides crucial information for risk stratification, surgical planning, and prognostication in lung cancer patients. When properly interpreted alongside other clinical data, it significantly improves patient selection for surgical intervention and helps predict long-term outcomes.