Noninvasive Pulmonary Nodule Elastometry by CT and Deformable Image Registration

Purpose/Objective(s): Stereotactic body radiation therapy (SBRT) is increasingly employed for the treatment of primary, recurrent, and oligometastatic lung tumors. The outcomes and toxicities of SBRT for central lung tumors are not well defined. We investigated our institutional experience using SBRT for central lung tumors. Materials/Methods: Our institutional SBRT database prospectively collects demographic and treatment-related data from all patients treated at our center. We retrospectively analyzed all patients with central lung tumors treated with SBRT between April 2008 and May 2013. The most common radiation dose was 50 Gy in five fractions delivered over consecutive days using coplanar plans. Dose constraints for organs at risk followed the recommendations of the American Association of Physicists in Medicine Task Group 101 report. Local control (LC) and overall survival (OS) were calculated using KaplanMeier estimates. Toxicity was graded using the Radiation Therapy Oncology Group Common Toxicity Criteria. Tumor response was scored using Response Evaluation Criteria in Solid Tumors v1.1. Predictors for toxicity, LC, and OS were analyzed using Cox proportional hazard regression models. Results: A total of 142 central lung tumors from 132 patients were identified and included for analysis. Median age was 71 years (range, 2491) and median follow up was 31.0 months (range, 2.5-62.5). There were 55 primary, 33 recurrent, and 54 metastatic tumors. Median tumor size was 2.1 cm (range, 0.5-5.5). Overall, there were 13 local failures resulting in 3-year LC rates of 94.2%, 91.7%, and 58.3%, in primary, recurrent, and metastatic lung tumors, respectively. There were 19 patients (14.4%) with grade 3 or higher pneumonitis including one grade 4 and one grade 5 toxicity. There were no grade 3 or higher acute toxicities. Rates of complete response, partial response, stable disease, and progressive disease were 34% (n Z 48), 45% (n Z 64), 20% (n Z 29), and 1% (nZ 1), respectively. The median survival for primary, recurrent, and metastatic lung tumors was 46.1, 43.6, and 16.5 months, respectively. Toxicity, LC, and OS were not associated with tumor size, radiation dose, or previous local therapy on univariate or multivariate analysis. Conclusions: SBRT for central lung tumors offers high rates of local control and acceptable toxicity rates comparable to published data for peripheral tumors. Patients with primary or recurrent lung tumors had comparable LC and OS which were better than patients with metastatic lung tumors. Appropriate patient selection and dose fractionation remains critical while outcomes from prospective trials mature. Author Disclosure: B. Mou: None. K.W. Merrell: None. D.A. Owen: None. K.E. Nelson: None. Y.I. Garces: None. K.R. Olivier: None.