Radiation Pneumonitis and Fibrosis

Epidemiology

  • Synergy of Radiation Therapy with Chemotherapeutic Agents: combination may potentiate radiation-associated lung damage
    • Cisplatin (see [[Cispaltin]])
    • Interferon-Gamma (see [[Interferon]])
    • Paclitaxel (see [[Paclitaxel]])

Physiology

  • Acute Effects of Radiation on Lung (within 3-12 weeks): primarily cytotoxic responses
    • Can occasionally involve areas outside of the radiation port
  • Chronic Effects of Radiation on Lung (within 3-6 months): primarily vascular
    • Initial injury to capillary and epithelium with fibrosis in subpleural and perivascular areas (without inflammatory cell infiltrate)
    • May result in pulmonary HTN

Pathology Patterns

  • Diffuse Alveolar Damage (see [[Diffuse Alveolar Damage]]): may result in diffuse alveolar hemorrhage or acute lung injury
  • Cryptogenic Organizing Pneumonia (see [[Cryptogenic Organizing Pneumonia]]): may be seen with diffuse alveolar damage
    • May occur outside of the treatment field (few reported cases, mostly in association with radiation treatment for breast cancer)
  • Cellular Interstitial Pneumonia: may be seen with DAD
  • Usual Interstitial Pneumonia (UIP): seen in some chronic cases

Clinical

Acute Radiation Pneumonitis

  • Epidemiology
    • 10% of irradiated patients develop acute radiation pneumonitis within 3 months of treatment
    • 43% of irradiated patients will eventually manifest some radiographic changes due to the radiation therapy
    • Latency: usually begins 3-8 wks after XRT (this would be too short for relapse from a primary disease for which radiation would be given, such as Hodgkin’s disease)
  • Diagnosis
    • CXR: sharp boundaries of infiltrates in the lung, demarcating the radiation port (infiltrates are especially apparent around the hilum)
      • Infiltrates uncommonly occur outside of the radiation port
    • FOB: may demonstrate lymphocytosis in ipsilateral lung and contralateral lung (ie: the uninvolved lung outside of the radiation port)
  • Clinical: fever, dyspnea, cough, pleuritic chest pain, crackles, hemoptysis (due to [[Diffuse Alveolar Hemorrhage]])
  • Diagnosis
    • CXR/CT Pattern: diffuse interstitial infiltrates with sharp boundaries (demarcating the radiation port), diffuse interstitial infiltrates (upper-lobe predominance), widened mediastinum, pleural effusion, “eggshell” calcifications of mediastinal nodes
  • Treatment: steroids
  • Prognosis
    • May spontaneously improve
    • May be rapidly fatal, despite steroids (in some cases)
    • Usually progresses to fibrosis

Chronic Radiation Fibrosis

  • Latency: usually begins 3-6 mo after XRT and becomes stable after 2 years
  • Diagnostic
    • CXR/CT Patterns: diffuse interstitial infiltrates with sharp boundaries (demarcating the radiation port), diffuse interstitial infiltrates (upper-lobe predominance), widened mediastinum, pleural effusion, “eggshell” calcifications of mediastinal nodes
  • Clinical: fatigue

Post-XRT Cryptogenic Organizing Pneumonia (see [[Cryptogenic Organizing Pneumonia]])

  • Epidemiology: reported in some breast cancer cases
  • Clinical: manifests as involvement of lung outside of the radiation port

Treatment

  • xxx

Prognosis

  • May rapidly progress to fatal outcome in some cases, despite steroids

References

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