Medical Image of the Week: Typical Pulmonary CT Findings Following Radiotherapy

Figure 1. Panel A: CT chest, lung windows, demonstrating a spiculated nodule, biopsy proven adenocarcinoma in the right lower lobe (arrow). Panel B: Eight months post stereotactic radiation therapy, there has been development of focal consolidation, with air bronchograms, involving the right middle and lower lobes. Notice the volumetric appearance. The primary malignancy is no longer identified as such. Panel C: Thirteen months later the consolidation has evolved into an area of volume loss, containing bronchiectasis, and sharp contours as a result of organized fibrosis.

Radiation-induced lung disease (RILD) commonly develops in patients treated with radiation for intrathoracic and chest wall malignancies.

There are two distinct radiographic patterns:

1. Radiation pneumonitis which occurs within 4-12 weeks after completion of therapy, and is characterized by development ground-glass opacities and/or consolidation in and around the treated lesion. A somewhat nodular or patchy appearance may occur. Typically, the affected tissue conforms to the radiation ports and may cross fissures/lobes. There may be milder similar changes in the contralateral lung.
2. A chronic phase, known as radiation fibrosis, is noticeable about 6-12 months post treatment and may progress up to 2 years, after which the findings tend to stabilize. In this stage, the areas of consolidation undergo volume loss, architectural distortion and may contain traction bronchiectasis. Linear and band scarring may also be seen. In this phase, sharper demarcation between normal and irradiated lung parenchyma is commonly seen.

Special attention to the typical radiological characteristics and timeline, in most cases allows to distinguish RILD from potential superimposed infection, subacute inflammatory diseases, locally recurrent neoplasm and radiation-induced neoplasms.

Andrew Erickson MS IV¹, Berndt Schmidt MD², Veronica Arteaga MD², Diana Palacio MD²

¹Midwestern University – Arizona College of Osteopathic Medicine

²Division of Thoracic Radiology, Department of Medical Imaging. University of Arizona, Tucson (AZ)

Reference

1. Choi YW, Munden RF, Erasmus JJ, Joo Park K, Chung WK, Jeon SC, Park CK. Effects of radiation therapy on the lung: radiologic appearances and differential diagnosis. Radiographics. 2004 Jul;24(4):985-97. [CrossRef] [PubMed]

Cite as: Erickson A, Schmidt B, Arteaga V, Palacio D. Medical image of the week: typical pulmonary CT findings following radiotherapy. Southwest J Pulm Crit Care. 2017;15(3):120-1. doi: https://doi.org/10.13175/swjpcc112-17 PDF

Medical Image of the Week: Pembrolizumab-induced Pneumonitis

Figure 1. Thoracic CT showing multifocal, bilateral extensive lung opacities consistent with consolidation with a striking peribronchovascular distribution. Note the opacities are primarily distributed along the airways. Peripheral lung opacity, both ground-glass opacity and consolidation, is also present.

Figure 2. Axial thoracic CT performed several months after Figure 1 following discontinuation of the pembrolizumab and initiation, and subsequent tapering, of corticosteroid therapy, shows significant regression in the previously noted extensive peribronchovascular consolidation. Residual areas of consolidation and ground-glass opacity associated with architectural distortion are consistent with scarring.

A 76-year-old man with metastatic melanoma, undergoing treatment with pembrolizumab, an antibody against programmed cell death 1 (PD-1), beginning 8 months ago developed low-grade fever, non-productive cough, and shortness of breath. A thoracic CT scan showed multifocal, bilateral extensive lung opacities (Figure 1). The patient underwent bronchoscopy with bronchoalveolar lavage which showed non-specific inflammatory changes associated with foci of organizing pneumonia. Microbiologic studies, including Coccioides antibody enzyme immunoassay and Aspergillus antigen, were negative.

The patient was begun on corticosteroid therapy for presumed medication-induced pulmonary injury, manifestation as an organizing pneumonia pattern, due to pembrolizumab. Over the ensuing months, his symptoms abated and his CT scan abnormalities regressed (Figure 2).

Organizing pneumonia may occur as an idiopathic, primary pulmonary process, often referred to as “cryptogenic organizing pneumonia,” or may occur in the context of a number of systemic conditions, a situation often referred to as secondary organizing pneumonia. Among the various etiologies of secondary organizing pneumonia, medication-induced pulmonary injury is fairly common and when imaging features of organizing pneumonia are seen, careful correlation regarding the possibility of a medication-induced etiology should be undertaken. Recently, three cases of pembrolizumab-induced pneumonitis were described, two being consistent with organizing pneumonia (1).

The thoracic CT findings of organizing pneumonia include peripheral and peribronchovascular consolidation and ground-glass opacity, areas of consolidation surrounding ground-glass opacity (often referred to as the “atoll” or reverse ground-glass halo” sign- see Medical Image of the Week: The Atoll Sign in Cryptogenic Organizing Pneumonia), single and multiple nodules, and perilobular consolidation. The case illustrates a dramatically peribronchovascular distribution of pulmonary consolidation as a manifestation of medication-induced organizing pneumonia.

Michael B. Gotway, MD

Department of Radiology

Mayo Clinic Arizona

Scottsdale, AZ USA

Reference

1. Leroy V, Templier C, Faivre JB, Scherpereel A, Fournier C, Mortier L, Wemeau-Stervinou L. Pembrolizumab-induced pneumonitis. ERJ Open Res. 2017 May 2;3(2). pii: 00081-2016. [CrossRef] [PubMed]

Cite as: Gotway MB. Medical image of the week: pembrolizumab-induced pneumonitis. Southwest J Pulm Crit Care. 2017;15(3):118-9. doi: https://doi.org/10.13175/swjpcc110-17 PDF