Can empyema be concurrent with immunotherapy-caused pneumonitis on computed tomography (CT) scans?

Concurrent Empyema and Immunotherapy-Induced Pneumonitis on CT Imaging

Empyema and immunotherapy-induced pneumonitis can occur concurrently and present with distinct radiographic patterns on CT imaging that allow for their differentiation.

Radiographic Differentiation

Immunotherapy-Related Pneumonitis (IRP) Features

• Presents with characteristic CT patterns including:
  • Ground glass opacities (most common finding)
  • Cryptogenic organizing pneumonia-like appearance
  • Interstitial pneumonia pattern 1
  • Multifocal patchy alveolar opacities
  • Bilateral nonsegmental distribution 1

Empyema Features

• Appears as:
  • Loculated pleural fluid collection
  • Pleural thickening and enhancement
  • Possible air-fluid levels
  • Usually unilateral and confined to pleural space

Diagnostic Approach

Initial Evaluation

1. High-resolution CT with contrast should be performed to identify both conditions 1

   • Thin-section CT (2.0-2.5 mm or less) with IV contrast is recommended 1
   • Both transverse and coronal reformatted images should be analyzed 1

2. Clinical correlation is essential:

   • Immunotherapy-related pneumonitis: dyspnea, cough, chest pain, fever, hypoxia 1
   • Empyema: fever, localized chest pain, productive cough, septic symptoms

Confirmatory Testing

• Bronchoalveolar lavage should be performed to:

  • Rule out infection or tumor infiltration 1
  • Collect samples for microbiological culture 1
  • Differentiate between infectious and non-infectious causes

• Pleural fluid sampling (if empyema is suspected):

  • Thoracentesis for pleural fluid analysis
  • Culture and sensitivity testing

Management Considerations

For Immunotherapy-Related Pneumonitis

1. Grade-based treatment approach:

   • Grade 1-2: Oral steroids (prednisone 1 mg/kg daily) 1
   • Grade 3-4: Hospitalization and high-dose IV corticosteroids (methylprednisolone 2-4 mg/kg/day) 1

2. Steroid-refractory cases:

   • Consider additional immunosuppressive agents:
     • Infliximab
     • Mycophenolate mofetil
     • Cyclophosphamide 1

For Empyema

1. Antimicrobial therapy targeting likely pathogens
2. Drainage procedures:
   • Tube thoracostomy
   • Video-assisted thoracoscopic surgery (VATS) if loculated

For Concurrent Conditions

• Prioritize treatment of both conditions simultaneously
• Careful monitoring for potential interactions between immunosuppressive therapy and antimicrobial treatment

Important Clinical Considerations

Diagnostic Pitfalls

• Immunotherapy-related pneumonitis can be misdiagnosed as:

  • Infectious pneumonia
  • Tumor progression
  • Radiation pneumonitis
  • Pulmonary edema 1

• Empyema can be confused with:

  • Pleural metastases
  • Complex pleural effusion
  • Lung abscess extending to pleura

Risk Factors for Concurrent Disease

• Patients with NSCLC have higher incidence of pneumonitis (up to 19%) 2
• Combination immunotherapy increases pneumonitis risk (10% vs 3% with monotherapy) 1
• Pre-existing lung disease increases risk for both conditions

Monitoring and Follow-up

• Follow-up CT imaging is essential to assess response to treatment for both conditions
• Timing of follow-up should be based on clinical context and severity 1
• Monitor for recurrence of pneumonitis during steroid tapering 1

Conclusion

While challenging, the concurrent diagnosis of empyema and immunotherapy-induced pneumonitis is possible through careful radiographic assessment and appropriate diagnostic testing. The distinct radiographic features of each condition allow for their differentiation on CT imaging, enabling appropriate management of both conditions simultaneously.