Clinical implementation of gated stereotactic radiotherapy and early treatment outcomes

Purpose: Stereotactic Ablative Body Radiotherapy (SABR) for early stage Non-Small Cell Lung Cancer (NSCLC) improves survival in patients unfit to undergo surgery and in elderly patients who are eligible for surgery.1,2,3 In patients with a limited number of pulmonary metastases SABR can result in excellent local control.4 We report on the clinical implementation of Gated SABR for lung indications and the early treatment results. Methods and materials: Clinical protocols were written for Gated SABR for patients with early stage NSCLC and pulmonary oligometastases. Prior to treatment a fiducial marker is inserted into the tumour under CT guidance. Target contouring is performed on 4DCT scans. A dedicated LINAC with ExacTrac Adaptive Gating is used for treatment. Continuous tracking of the implanted marker ensures accuracy of tumour position in the selected gating windows during treatment. The proposed fractionation schedules for NSCLC are risk adapted.5 Data on treatment planning and clinical follow up are collected in a prospective database. Results: The programme commenced September 2011 and 13 patients were eligible for treatment. Currently 8 patients (with a total of 9 tumours) have completed treatment. All but two patients were deemed medically inoperable. Two patients refused surgery. Marker insertion was complicated by pneumothorax in 8 patients, one of whom required a thoracic drain. Treatment side effects were mild, limited to slight coughing and fatigue. Radiological evaluation after 3 months (six patients) showed a good response with reduction in tumour size in 5 and a complete response in 1 patient; after 6 months, 2 patients showed an ongoing response. 2 Patients developed further metastases outside the treatment field, one in, one outside the thorax. Further follow up data will be presented at the meeting. Conclusion: Gated SABR is feasible and well tolerated. With limited follow up our experience mirrors the high control rates reported in the literature.