Estimation of Radiation-induced Secondary Cancer Risks for Early-stage Non-Small-Cell Lung Cancer Patients after Stereotactic Body Radiotherapy

Publication date: Available online 19 October 2016
Source:Practical Radiation Oncology
Author(s): Chunhui Han, Timothy E Schultheiss, Jeffrey Y C Wong
Purpose/ObjectivesIn this study, we evaluated radiation-induced secondary lung cancer risks for the lung and the breast from SBRT treatment of early-stage non-small cell lung cancer (NSCLC) with different radiotherapy treatment modalities.Materials/MethodsTen patients (five male and five female) with early-stage NSCLC who received definitive SBRT treatments were retrospectively selected. For each patient, two three-dimensional conformal radiotherapy (3D–CRT) plans using 6 MV and 10 MV photons respectively, a helical tomotherapy (HT) plan, and two volumetric modulated arc therapy (VMAT) plans using one and two arcs, respectively, were generated. The excess absolute risk (EAR) for secondary cancer occurrence was calculated using three organ equivalent dose (OED) models: the linear-exponential model, the plateau model, and the linear model, for prescription dose range of 30 to 70Gy.ResultsThe 3D–CRT plans showed significantly lower monitor units compared to the rotational IMRT plans. Based on each of the three OED models, HT and VMAT plans showed comparable average EAR's to both the lung and the breast compared to the 3D–CRT plans in the prescription dose range of 30 to 70Gy. At a prescription dose of 50Gy and using the linear-exponential model, the average lung EAR estimation ranged from 15.7±5.3 to 16.0±6.5 per 10,000 patients per year with the five delivery techniques, and the average EAR estimation for the breast ranged from 18.0±14.0 to 21.0±15.0 per 10,000 patients per year. The secondary cancer risk increased approximately linearly with mean organ dose. The 3D–CRT plans showed significantly higher secondary cancer risk for the ipsilateral lung, and lower risk for the contralateral lung, compared to the HT and VMAT plans.ConclusionRotational IMRT techniques including helical tomotherapy and VMAT do not increase secondary cancer risks for the lung or the breast compared to 3D–CRT techniques, despite higher monitor units used.



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