Is a patient with suspected immunotherapy-induced pneumonitis requiring 2L/min of oxygen considered to have low or medium-grade pneumonitis?

Grading of Immunotherapy-Induced Pneumonitis

A patient with suspected immunotherapy-induced pneumonitis requiring 3L/min of oxygen is considered to have grade 2 (moderate) pneumonitis according to current guidelines. 1

Pneumonitis Grading System

Immune checkpoint inhibitor (ICI) pneumonitis is graded based on clinical symptoms and oxygen requirements:

• Grade 1 (Mild): Asymptomatic; clinical or diagnostic observations only; radiographic findings only
• Grade 2 (Moderate): Symptomatic; requiring supplemental oxygen (nasal cannula or similar low-flow device)
• Grade 3 (Severe): Severe symptoms; limiting self-care ADLs; requiring high-flow oxygen (>6L/min), non-invasive ventilation, or hospitalization
• Grade 4 (Life-threatening): Life-threatening respiratory compromise requiring urgent intervention (e.g., intubation)
• Grade 5: Death

Rationale for Grade 2 Classification

The Society for Immunotherapy of Cancer (SITC) guidelines specifically indicate that patients requiring supplemental oxygen via nasal cannula or similar low-flow devices fall into the grade 2 category 1. Your patient requiring 3L/min of oxygen fits this classification.

This grading is important because it directly impacts management:

• Grade 2 pneumonitis requires:
  • Withholding immunotherapy
  • Initiating oral/intravenous corticosteroids (typically prednisone 1-2 mg/kg/day or equivalent)
  • Close monitoring with follow-up chest CT prior to next scheduled immunotherapy dose
  • Consideration of bronchoscopy if infiltrates persist or worsen

Clinical Considerations

Several factors support the grade 2 classification:

1. The oxygen requirement of 3L/min indicates significant but not severe respiratory compromise
2. According to the British Thoracic Society guidelines, this level of oxygen supplementation falls within the range typically delivered via nasal cannula (1-6 L/min) 1
3. The patient's oxygen requirement has not escalated to high-flow oxygen (>6L/min) which would indicate grade 3 pneumonitis

Management Implications

The grade 2 classification has important management implications:

• Drug withdrawal: Immunotherapy should be withheld until resolution of pneumonitis 1
• Corticosteroids: Initiate oral/IV corticosteroids with a slow taper over 4-6 weeks minimum 1
• Monitoring: Close follow-up with repeat chest CT prior to considering any rechallenge 1
• Diagnostic workup: Consider bronchoscopy with bronchoalveolar lavage to rule out infection and confirm lymphocytosis typical of ICI pneumonitis 2

Pitfalls to Avoid

1. Rapid steroid tapering: Recrudescence of pneumonitis commonly occurs when steroids are tapered too quickly, particularly below 10mg prednisone equivalent 2
2. Premature rechallenge: Reintroducing immunotherapy before complete resolution of infiltrates increases risk of recurrent, potentially more severe pneumonitis
3. Overlooking chronic pneumonitis: Approximately 2% of patients develop chronic ICI pneumonitis requiring ≥12 weeks of immunosuppression 2
4. Missing concomitant infection: Always rule out infectious causes before attributing respiratory symptoms solely to immunotherapy

Conclusion

Based on current guidelines and the patient's oxygen requirement of 3L/min, this case represents grade 2 (moderate) immunotherapy-induced pneumonitis. This classification guides appropriate management decisions including immunotherapy withholding, corticosteroid initiation, and monitoring protocols.