Dose escalation with the frameless respiratory tumor tracking system of the cyberknife for early stage non-Small-Cell Lung cancer

Abstract

8.1 Abstract: We used the respiratory movement tracking system of the CyberKnife®, called Synchrony® (Accuray Incorporated, Sunnyvale, CA), to develop dose plans delivering 45 Gy (3 times 15 Gy) for the treatment of early stage non-small cell lung cancer (NSCLC). Characteristics of those plans were compared with plans developed for 3-Dimensional conformal radiotherapy (3D-CRT) administering 60 Gy (20 times 3 Gy) based on a slow CT. Ten patients with Stage I NSCLC previously treated with 3DCRT were replanned with the CyberKnife treatment planning system. In the 3D-CRT plan, the planning target volume (PTV) equaled the gross tumor volume (GTV)slow + 15 mm. In the CyberKnife plan, the PTV equaled the GTV + 8 mm. The physical dose of both treatment plans was converted into the normalized total dose using the linear quadratic model with an α/βtumor = 10 Gy and α/β organs at risk(OAR) = 3 Gy. The mean doses administered to the PTV with the CyberKnife and 3D-CRT were 115.8 Gy and 66 Gy, respectively (p < 0.0001). The mean V20 of the CyberKnife and 3D-CRT plan was 8.2% and 6.8%, respectively (p=0.124). Both plans respected the constraints of the other organs at risk (OAR). In this context the CyberKnife can administer a much higher biological dose than 3D-CRT without increasing the dose (V20) to the lungs. © 2007 Springer-Verlag Berlin Heidelberg.