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)
