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Purpose: To verify the accuracy of volumetric arc therapy (VMAT) using the RapidArc™ device when switching patients from one single linear accelerator (linac) to a paired energy and mechanics "twin" linac without reoptimization of the original treatment plan.Patients and Methods: Four centers using 8 linacs were involved in this study. Seventy-four patients previously treated with the 6MV photon RapidArc™ technique were selected for analysis, using 242 measurements. In each institution, all patients were planned on linac A, and their plans were verified both on linac A and on the twin linac B. Verifications were done using the amorphous silicium electronic portal imager (EPID) of the linacs and were analyzed with the EpiQa software (Epidos, Bratislavia, Slovakia). The gamma index formalism was used for validation with a double threshold of 3 % and 3 mm with a measurement resolution of 0.39 mm/pixel, and a smoothed resolution of approximately 2.5 mm.Results: The number of points passing the gamma criteria between the measured and computed doses was 94.79 ± 2.57 % for linac A and 94.61 ± 2.46 % for linac B. Concerning the smoothed measurement analysis, 98.67 ± 1.26 % and 98.59 ± 1.20 % points passing the threshold were obtained for linacs A and B, respectively. The difference between the 2 dose matrices acquired on the EPID was very small, with 99.92 ± 0.06 % of the points passing the criteria.Conclusion: For linacs sharing the same mechanical and energy parameters, this study tends to indicate that patients may be safely switched from treatment with one linac to treatment with its twin linac using the same VMAT plan. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: Chemoradiotherapy is the standard treatment of inoperable and/or non-resectable IIIA/B non-small-cell lung cancer (NSCLC). Aware of the necessity to increase local control in locally advanced NSCLC, we analyzed the feasibility of high-dose three-dimensional conformal radiation therapy (3D-CRT) in the treatment of localised NSCLC. Patients and methods: We undertook a retrospective analysis of consecutive patients with non-resectable NSCLC treated with high-dose (74Gy) standard-fractionation 3D-CRT, with particular attention to the relationship between lung and heart radiation-induced toxicities. Results: Fifty patients (41 males, 9 females) were included. A total of 35 (70%) patients received the planned total dose of 74Gy. Patients irradiated to inferior doses interrupted the treatment because of limiting toxicities. Induction and concurrent chemotherapy was delivered to 39 (78%) and 14 (28%) patients, respectively. Eight (16%) patients experienced grade 3-4 acute lung toxicity, all of them having a history of pulmonary disease, a FEV1 below 1.6 L, and a lung V20 of at least 25%. Three (6%) patients were deemed to experience radiation-induced cardiac toxicity. Conclusions: This study assesses the feasibility of delivering a total dose of 74 Gy combined with chemotherapy in locally advanced NSCLC. High lung and heart V20 increases the risk of radiation-induced lung and cardiac toxicity, the later being highly difficult to precisely assess, as late deaths are rarely documented, and responsibility of the treatment might be often underestimated. The precise evaluation of cardiac condition may be helpful to spare fragile patients from potentially toxic effects of high-dose radiation, especially in controlled trials. [Copyright &y& Elsevier]