Preclinical Model of Stereotactic Ablative Lung Irradiation Using Arc Delivery in the Mouse: Effect of Beam Size Changes and Dose Effect at Constant Collimation

• Published in: International journal of radiation oncology, biology, physics Vol. 107; no. 3; pp. 548 - 562
• Main Authors: Bertho, Annaïg, Dos Santos, Morgane, Buard, Valérie, Paget, Vincent, Guipaud, Olivier, Tarlet, Georges, Milliat, Fabien, François, Agnès
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-07-2020; Elsevier
• Subjects: Animals; Bronchiolitis - etiology; Cell Count; Disease Models, Animal; Dose-Response Relationship, Radiation; Epithelial Cells - pathology; Epithelial Cells - radiation effects; Fibrosis; Life Sciences; Lung - pathology; Lung - radiation effects; Male; Mice; Radiosurgery - adverse effects; Survival Analysis
• ISSN: 0360-3016; 1879-355X
• DOI: 10.1016/j.ijrobp.2020.03.011

Stereotactic body radiation therapy is a therapeutic option offered to high surgical risk patients with lung cancer. Focal lung irradiation in mice is a new preclinical model to help understand the development of lung damage in this context. Here we developed a mouse model of lung stereotactic therapy using arc delivery and monitored the development of lung damage while varying the beam size and dose delivered.
C57BL/6JRj mice were exposed to 90 Gy focal irradiation on the left lung using 1-mm diameter, 3 × 3 mm2, 7 × 7 mm2, or 10 × 10 mm2 beam collimation for beam size effect and using 3 × 3 mm2 beam collimation delivering 20 to 120 Gy for dose effect. Long-term lung damage was monitored with micro–computed tomography imaging with anatomopathologic and gene expression measurements in the injured patch and the ipsilateral and contralateral lungs.
Both 1-mm diameter and 3 × 3 mm2 beam collimation allow long-term studies, but only 3-mm beam collimation generates lung fibrosis when delivering 90 Gy. Dose-effect studies with constant 3-mm beam collimation revealed a dose of 60 Gy as the minimum to obtain lung fibrosis 6 months postexposure. Lung fibrosis development was associated with club cell depletion and increased type II pneumocyte numbers. Lung injury developed with ipsilateral and contralateral consequences such as parenchymal thickening and gene expression modifications.
Arc therapy allows long-term studies and dose escalation without lethality. In our dose-delivery conditions, dose-effect studies revealed that 3 × 3 mm2 beam collimation to a minimum single dose of 60 Gy enables preclinical models for the assessment of lung injury within a 6-month period. This model of lung tissue fibrosis in a time length compatible with mouse life span may offer good prospects for future mechanistic studies.