CT appearance of radiation injury of the lung after stereotactic body radiation therapy (SBRT) for lung cancers: a pictorial review

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1 CT appearance of radiation injury of the lung after stereotactic body radiation therapy (SBRT) for lung cancers: a pictorial review Award: Certificate of Merit Poster No.: C-210 Congress: ECR 2009 Type: Educational Exhibit Topic: Chest Authors: A. Linda, M. Trovo, C. Javidan-Nejad, J. Bradley ; Udine/IT, Aviano/IT, St.Louis, MO/US Keywords: lung cancer, Radiation pneumonitis, Radiation fibrosis, Stereotactic Body Radiation Therapy DOI: /ecr2009/C-210 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 30

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3 Learning objectives To review the serial CT manifestations of radiation injury to the lung after Stereotactic Body Radiation Therapy (SBRT) for lung cancers. Background Stereotactic Body Radiation Therapy (SBRT) Stereotactic Body Radiation Therapy (SBRT) is a newly emerging radiotherapy treatment method to deliver a potent ablative dose to deep-seated tumors in the lung, liver, spine, pancreas and kidney. SBRT involves constructing very compact high-dose volumes in and about the tumor, that fall off very rapidly in all directions. This is achieved through sophisticated image guidance and delivery technologies with subcentimetric accuracy (1,2). SBRT for lung cancers INDICATIONS: 1.Medically inoperable patients with early stage NSCLC - T1 N0 M0 - T2 (<5 cm) N0 M0 - T3 (<5 cm) N0 M0 (chest wall primary tumors only) 2. Selected patients with lung metastases - Sarcoma - Colorectal carcinoma - Melanoma TECHNIQUE: In order to obtain an extremely conformal dose distribution, multiple (10-12) highly collimated high-dose beams are used. The target for high-dose conformal coverage is constituted by the gross tumor volume and an accounting for organ motion. Page 3 of 30

4 The THIN SHELL OF NORMAL LUNG immediately outside the tumor is exposed to a significant radiation dose, while the remaining lung parenchyma is spared (Fig.1 on page ) (1,2). Conventional Radiation Therapy (CRT) for lung cancers TECHNIQUE: 2-4 coplanar photon beams are used to deliver tumoricidal dose of radiation to tumors. In addition, a LARGE VOLUME of normal lung is exposed to a significant radiation dose (Fig.2 on page ). CT CHANGES AFTER CRT FOR LUNG CANCERS: Radiologic manifestations are confined to the lung tissue within the radiation port and are dependent on the interval after completion of treatment (Fig.3 on page ). In the EARLY phase (1-6 months after CRT), the most frequent manifestations are the following (Fig.4 on page )(3): Ground-glass opacities and/or consolidation Nodular and focal consolidative opacities Occasionally, ipsilateral pleural effusion In the LATE phase (6-24 months after CRT), the most common findings are the following (Fig.5 on page )(3): Consolidation (with sharp borders) Volume loss Linear scarring Traction bronchiectasis Occasionally in association with ipsilateral displacement of the mediastinum and adjacent pleural thickening or effusion. Page 4 of 30

5 Images linked within the text of this section: Fig.: SBRT is characterized by the use of multiple coplanar and non-coplanar fields which confine the high-dose region to the neoplasm but simultaneously smear the low-dose region over large parts of the lung. The reduced volume of pulmonary tissue within the target volume and highly conformal dose distribution limit the toxicity of SBRT and affect the CT appearance of the lung parenchyma after treatment. Page 5 of 30

6 Fig.: In CRT, few coplanar fields are used. This results in exposure of a large volume of normal lung to significant radiation dose. Page 6 of 30

7 Fig.: Two distinct clinical and radiologic stages are recognized in CRT-induced lung disease: an early, transient stage (1-6 months after completion of radiation therapy), characterized by radiation pneumonitis, and a later stage (6-24 months after completion of radiation therapy), characterized by chronic radiation fibrosis. Page 7 of 30

8 Fig.: NSCLC in 50-year-old man. CT scan obtained 7 weeks after completion of CRT shows discrete consolidation and GGO conforming to the radiation port (arrows).note that CT changes have a defined, non anatomic margination and cross the fissures, following the outline of radiation port! Page 8 of 30

9 Fig.: NSCLC in 56-year-old man. CT scan obtained 16 months after completion of CRT demonstrates a well-defined area of consolidation with bronchiectasis conforming to the radiation port (arrows) and volume loss of the right lung.note that CT changes have a geometric shape and sharp borders, following the outline of radiation port! Page 9 of 30

10 Imaging findings OR Procedure details CT changes after SBRT for lung cancers The complex distribution of radiation dose of SBRT and the very high dose per-fraction result in patterns of lung injury that are different than those of conventional radiation therapy (CRT). Similarly to CRT, CT findings after SBRT can be separated into early (3-6 months after SBRT) and late (>6months after SBRT) (Fig.6 on page ) (4-9). EARLY findings (3-6 months after SBRT): radiation pneumonitis CT PATTERNS (4-9): Diffuse consolidation (Fig.7 on page ): diffuse, homogeneous increase in pulmonar parenchymal attenuation that obscures the margins of vessels and airway walls. Diffuse ground-glass opacity (Fig.8 on page ): hazy increased attenuation of lung, with preservation of bronchial and vascular margins. Patchy consolidation and ground-glass opacity (Fig.9 on page ): patchy areas of hazy and dense increased attenuation of lung, not completely filling the high-dose region. Patchy ground-glass opacity (Fig.10 on page ): patchy areas of hazy increased attenuation interspersed in normal parenchyma, not completely filling the high-dose region. No change (Fig.11 on page ): no evidence of increased density within the high-dose region. RADIOLOGIC-PATHOLOGIC CORRELATION: The histopathologic changes underlying the above-described early CT patterns are shown in Fig.12 on page. DIFFERENTIAL CONSIDERATIONS: Criteria that allow to distinguish SBRT-induced early changes from other pulmonary pathologic conditions are summarized in Fig.13 on page (10). LATE findings (>6 months after SBRT): radiation fibrosis CT PATTERNS (4-9): 1. Modified conventional pattern (Fig.14 on page ): consolidation, volume loss, bronchiectasis, similar to, but less extensive than conventional radiation fibrosis. Page 10 of 30

11 Mass-like pattern (Fig.15 on page ): focal consolidation limited around the tumor. Scar-like pattern (Fig.16 on page ): linear opacity in the region of the tumor associated with volume loss. No changes (Fig.17 on page ): no evidence of increased density within the high-dose region. RADIOLOGIC-PATHOLOGIC CORRELATION: The histopathologic changes underlying the above-described late CT patterns are shown in Fig.18 on page. DIFFERENTIAL CONSIDERATIONS: Criteria that allow to distinguish SBRT-induced late changes from other pulmonary pathologic conditions are summarized in Fig.19 on page (10). Complications and associated findings (Fig.20 on page ) Pleural effusions (early and late) Lung infection (early and late) Rib fracture (late) Page 11 of 30

12 Images linked within the text of this section: Fig.: Like CRT-induced lung disease, SBRT-induced lung injury is divided into an early clinical and radiologic phase (3-6 months after completion of radiation therapy) and a late clinical and radiologic phase (6-24months after completion of radiation therapy). Note that early damage occurs later than in case of CRT (3 months versus 1 month after completion of treatment)(see Fig.3). Page 12 of 30

13 Fig.: NSCLC in 83-year-old man.ct scan obtained 4 months after SBRT demonstrates a "stellate" area of homogeneous increase in parenchymal attenuation that obscures the margins of vessels and airway walls. Note the presence of air bronchogram (arrow) within the area of consolidation, a sign that suggests that the alveoli are filled with exudates, hyaline membranes and cells (see Radiologic-pathologic correlation, Fig.12). Page 13 of 30

14 Fig.: NSCLC in 80-year-old man.ct scan obtained 5 months after SBRT demonstrates a well defined area of hazy increased attenuation of the lung parenchyma, with preservation of bronchial and vascular walls. Page 14 of 30

15 Fig.: NSCLC in 66-year-old woman.ct scan obtained 5 months after SBRT shows patchy areas of hazy and dense increased attenuation of the lung parenchyma, not completely filling the high-dose region.note that the change in attenuation crosses the pleural fissure (arrows), unlike in other parenchymal lung diseases (infections, BOOP/COP, BAC, etc). Page 15 of 30

16 Fig.: NSCLC in 75-year-old woman.ct scan obtained 4 months after SBRT shows patchy areas of hazy increased attenuation (arrows) interspersed in normal parenchyma, not completely filling the high-dose region.n=nodule Page 16 of 30

17 Fig.: NSCLC in 78-year-old man.ct scan obtained 4 months after SBRT (b) demonstrates no evidence of increased density within the high-dose region compared to the baseline CT scan (a). Also note that the nodule is decreased in size (arrow). Page 17 of 30

18 Fig.: During the early phase after SBRT, both the alveolar epithelium and the endotelium are injured; as a consequence, alveoli are filled with hyaline membranes and capillaries are obstructed by fibrin and platelets. Page 18 of 30

19 Fig.: NSCLC in 75-year-old man.ct scan obtained 7 months after SBRT demonstrates an irregular area of consolidation with bronchiectasis (arrow) and volume loss of the irradiated lung. These findings are very similar to, but less extense than those occurring after CRT (see Fig.5). Page 19 of 30

20 Fig.: NSCLC in 52-year-old man.ct scan obtained 11 months after SBRT demonstrates an ill-defined mass-like area of consolidation (arrow). This appearance is indistinguishable from a recurrence. Page 20 of 30

21 Fig.: NSCLC in 52-year-old man.coronal CT image obtained 10 months after SBRT demonstrates a linear opacity (red arrow) in the region where the tumor was seated, associated with volume loss.note also blunting of the right costo-phrenic angle (white arrow), caused by pleural effusion. Page 21 of 30

22 Fig.: NSCLC in 63-year-old woman.ct scan obtained at baseline (a), 11 months (b) and 22 months (c) after SBRT show that there is no evidence of increased density within the radiation port. Note shrinking of the nodule (arrow). Page 22 of 30

23 Fig.: The istopathologic appearance of the late phase of injury after SBRT is dominated by progressive alveolar septal thickening and vascular sclerosis. Page 23 of 30

24 Fig.: Pulmonary diseases that can be mimicked by late CT changes occurring after SBRT are reported. Hints that might be helpful for differential diagnosis are provided in the right column.mimicking patterns: 1: modified conventional pattern, 2: mass-like, 3: scar-like. Page 24 of 30

25 Fig.: Pleural effusion on the irradiated side and pulmonary infection can develop both in the early and late phase of treatment. Fractures of ribs adjacent to the irradiated area rarely occur within a year after completion of radiation therapy. Page 25 of 30

26 Fig.: Pulmonary diseases that can be mimicked by early CT changes occurring after SBRT are reported. Hints that might be helpful for differential diagnosis are provided in the right column.mimicking patterns: 1: diffuse consolidation, 2: diffuse ground-glass opacity, 3: patchy consolidation and ground-glass opacity, 4: patchy ground-glass opacity. Page 26 of 30

27 Conclusion CT changes after SBRT are different than those developing after CRT (Fig.21 on page ), as they reflect the complexity of dose distribution and they usually involve just the "shell" of normal tissue outside the tumor. SBRT-induced injury of the lung can have variable CT appearance, and five early and four late patterns have been described. Differential diagnosis with other pulmonary diseases can be challenging; in particular, tumor recurrence can be very difficult to separate from early diffuse or patchy consolidation and late mass-like pattern. Knowledge of the temporal relationship of radiologic manifestions to SBRT can be useful in differential diagnosis with superimposed lung disease. Images linked within the text of this section: Page 27 of 30

28 Fig.: SBRT-induced CT changes are different than those developing after CRT: they are confined to a more limited area, have an irregular, stellate appearance and begin about 3 months after treatment. These differences are due to the different technique and dose distribution (see Fig.1 and Fig.2). Page 28 of 30

29 Personal Information Anna Linda Istituto di Radiologia Azienda Ospedaliero-Universitaria Udine - ITALY annalinda33@gmail.com References 1. Bradley J. Radiographic response and clinical toxicity following SBRT for stage I lung cancer. J Thorac Oncol. 2007;2:S Timmerman RD, Kavanagh BD, Cho LC, et al. Stereotactic body radiation therapy in multiple organ sites. J Clin Oncol. 2007;25: Choi YW, Munden RF, Erasmus JJ, et al. Effects of radiation therapy on the lung: radiologic appearances and differential diagnosis. Radiographics. 2004;24: Guckenberger M, Heilman K, Wulf J, et al. Pulmonary injury and tumor response after stereotactic body radiotherapy (SBRT): results of a serial follow-up CT study. Radiother Oncol. 2007;85: Kimura T, Matsuura K, Murakami Y, et al. CT appearance of radiation injury of the lung and clinical symptoms after stereotactic body radiation therapy (SBRT) for lung cancers: are patients with pulmonary emphysema also candidates for SBRT for lung cancers? Int J Radiat Oncol Biol Phys. 2006;66: Takeda T, Takeda A, Kunieda E, et al. Radiation injury after hypofractionated stereotactic radiotherapy for peripheral small lung tumors: serial changes on CT. Am J Roentgenol. 2004;182: Aoki T, Nagata Y, Negoro Y, et al. Evaluation of lung injury after threedimensional conformal stereotactic radiation therapy for solitary lung tumors : CT appearance. Radiology 2004;230: Ikezoe J, Takashima S, Morimoto S, et al. CT appearance of acute radiation-induced injury in the lung. Am J Roentgenol. 1998;150: Koenig TR, Munden RF, Erasmus JJ, et al. Radiation injury of the lung after three-dimensional conformal radiation therapy. Am J Roentgenol. 2002;178: Sagel SS. Lung. In: Lee JKT, Sagel SS, Stanley RJ, Heiken JP, eds. Computed body tomography with MRI correlation. 4th edn. Lippincott Williams & Wilkins, 2006: Page 29 of 30

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