Fatal Radiation Pneumonitis: Literature Review and Case Series

Abstract

Purpose: Fatal radiation pneumonitis is a rare event. In recent years, higher incidences of grade 5 pneumonitis have been reported. Based on 3 cases in our clinic, a literature review was performed to assess specific clinical features and risk factors for fatal pneumonitis.

Methods and materials: Three patients with nonsmall cell lung cancer were treated with conventionally fractionated radiation therapy, 2 with volumetric modulated arc therapy and one with intensity modulated radiation therapy. All 3 patients had high volumes of 5 Gy in the total lung and contralateral lungs. Patients died of pneumonitis between 2 and 5 months after the end of radiation therapy. A literature review focused on grade 5 pneumonitis was performed for conventionally fractioned and stereotactic radiation therapy for lung cancer.

Results: Patients with grade 5 pneumonitis develop symptoms sooner than lower grade pneumonitis. Symptoms often do not respond to steroid treatment or return after steroid taper. Imaging features extend beyond the high dose area and involve the contralateral lung. Dosimetric risk factors include both low dose and high dose lung volumes. For patients undergoing stereotactic radiation therapy interstitial lung disease has been described as a risk factor.

Conclusions: Despite decades of investigating radiation pneumonitis, the question of the optimum dose distribution in the lung, a large dose to a small volume versus a small dose to a large volume, is still unresolved. When both low and high dose lung volume constraints are followed, the risk for grade 5 pneumonitis has been shown to be low even with intensity modulated radiation therapy and concurrent chemotherapy. In addition to dose factors, underlying clinical and radiographic parameters play an important role for the development of grade 5 pneumonitis.

Figure 1

Radiographic lung changes at the onset of pneumonitis symptoms. Computed tomographic images at the time of radiation pneumonitis diagnosis were deformably registered to the planning computed tomographies. Isodose lines approximating the interstitial lung changes were overlaid. For each patient, the isodose line that visually overlapped best with the observed lung changes is presented (patient A, 11 Gy; patient B, 9 Gy; patient C, 15 Gy). Shown are coronal (top) and axial (bottom) planes for each patient. In addition to the groundglass changes in patient A and B, patient C also had a pleural effusion and disease progression in both lungs with increasing lung metastases. Although low dose lines matched the lung changes well in patient A, the overlap area was less for patient B and particularly C indicating that dose levels vary between patients.