D. Mathieu

Severe radiation pneumonitis after lung stereotactic ablative radiation therapy in patients with interstitial lung disease

PURPOSE To investigate the incidence and predictive factors of severe radiation pneumonitis (RP) after stereotactic ablative radiation therapy (SABR) in early-stage lung cancer patients with preexisting radiological interstitial lung disease (ILD). METHODS AND MATERIALS A retrospective analysis of patients with stage I lung cancer treated with SABR from 2009 to 2014 was conducted. Interstitial lung disease diagnosis and grading was based on pretreatment high-resolution computed tomography imaging. A central review of pretreatment computed tomography by a single experienced thoracic radiologist was conducted. Univariate and multivariate analyses were conducted to determine potential predictors of severe RP in patients with ILD. RESULTS Among 504 patients treated with SABR in this period, 6% were identified as having preexisting ILD. There was a 4% rate of ≥ grade 3 RP in the entire cohort. Interstitial lung disease was associated with increased risk of ≥ grade 3 RP (32% in ILD+ vs 2% in ILD-, P < .001). Five patients (21%) with ILD developed grade 5 RP. Lower forced expiratory volume in 1 second and forced vital capacity, higher V5Gy and mean lung dose, presence of severe radiological ILD, and combined emphysema were significant predictors of ≥ grade 3 RP on univariate analysis; only forced expiratory volume in 1 second remained on multivariate analysis. CONCLUSION Interstitial lung disease is associated with an increased risk of severe RP after SABR. Chest imaging should be reviewed for ILD before SABR, and the risk of fatal RP should be carefully weighed against the benefits of SABR in this subgroup.

Long-term quality of life in early-stage non-small cell lung cancer patients treated with robotic stereotactic ablative radiation therapy

PURPOSE The purpose of this study was to prospectively evaluate the quality of life (QoL) and pulmonary function of patients with early-stage non-small cell lung cancer treated with robotic stereotactic ablative radiation therapy (SABR). METHODS AND MATERIALS Eligible patients all had histologically confirmed stage I non-small cell lung cancer and were not surgical candidates because of poor pulmonary function, comorbidities, or refusal of surgery. SABR was delivered at a median dose of 60 Gy in 3 fractions for peripheral tumors and 50 Gy in 4 or 5 fractions for central tumors. QoL was scored using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire C30 (QLQ-C30) and Lung Cancer-13 questionnaires. Pulmonary function tests (PFTs) included forced expiratory volume in 1 second (FEV1) and lung diffusion capacity. Changes over time in QoL scores and PFTs were tested with nonparametric tests for longitudinal data. Local control, survival, and toxicities are also presented. RESULTS From January 2010 to May 2013, 45 patients were enrolled. Median follow-up was 41 months. QLQ-C30 mean baseline scores for global QoL and physical functioning were 66 ± 20% and 73 ± 22%. Multilevel analyses showed no statistically and clinically significant (10-point change) deterioration in any of the QoL scores after SABR. Mean baseline FEV1 was 1.39 ± 0.51 L, and mean lung diffusion capacity was 63 ± 25% of predicted. We saw no significant change in PFTs at any time point. At 3 years, local control, disease-free survival, and overall survival were, respectively, 94%, 67%, and 75%. CONCLUSIONS In nonsurgical patients with multiple comorbidities, lung SABR achieves long-term local control while maintaining QoL and pulmonary function.

Accuracy of Breath-hold CT in Treatment Planning for Lung Stereotactic Ablative Radiotherapy

PURPOSE The objectives of this study are (1) to measure concordance of tumor position on breath-hold (BH) computed tomography (CT) scans relative to the natural tumor path during free breathing (FB) and (2) to evaluate the benefits of the breathing monitoring device Abches (Apex Medical, Tokyo) for stereotactic ablative radiotherapy (SABR) treatment planning. METHODS In 53 lung cancer patients treated with CyberKnife™ robotic radiosurgery system, FB four-dimensional computerized tomography (4DCT) and end-expiration (EE) BH CT images were obtained. Extent of natural tumor motion was assessed with rigid registration derived from end-inspiration (EI) and EE phases of the 4DCT. Tumor displacement in BH scans relative to the natural tumor path was measured relative to the EE 4DCT phase. RESULTS Mean tumor motion (+/- 1 SD) during natural FB was 1 ± 1 mm, 2 ± 2 mm, and 6 ± 6 mm in medio-lateral, anterior-posterior, and cranio-caudal directions, respectively. Tumor position on BH CT scan was closer to EE than EI 4DCT phase for 35/53 patients (66%). Difference of BH tumor position vs. EE state was 4 ± 3 mm. Gross tumor displacements perpendicular to natural tumor path were as great as 11 mm (anterior-posterior) and were seen with or without the breathing monitoring device. CONCLUSION Tumor position during BH CT may not accurately correspond to positions observed on FB 4DCT. Hence, accurate and custom 4D analysis for each individual patient is recommended for treatment planning, especially those involving BH acquisitions.

The impacts of mid‐treatment CBCT‐guided patient repositioning on target coverage during lung VMAT

The purpose of this study is quantify intrafraction motion (IFM) during lung volumetric‐modulated arc therapy (VMAT) and evaluate the impact of mid‐treatment cone beam computed tomography (CBCT)‐guided patient repositioning on target coverage.

151: Does MID-Treatment CBCT-Guided Patient Repositioning During Lung VMAT Impact Target Coverage?

Purpose: The objectives of this study are to (1) quantify intrafraction motion (IFM) during lung volumetric-modulated arc therapy (VMAT) and (2) evaluate the impact of mid-treatment patient repositioning after cone beam computed tomography (CBCT) acquisition upon target coverage. Method: This analysis included lung tumors treated with VMAT between April 2012 and June 2015 with 50-60 Gy in 3-5 fractions. Treatment planning consisted of a four-dimensional (4D) CT scan from which an internal target volume (ITV) delineation was performed. A 5 mm margin was added in all directions to obtain the final planning target volume (PTV). Treatment sessions were performed in supine position with a customized dual vacuum immobilization device (BodyFIX, Elekta, Stockholm, Sweden). All patients underwent pre and mid-treatment CBCTs to ensure proper repositioning. Following each CBCT, a two-step rigid registration was performed by an experienced radiation oncologist according to the planning CT, taking into account organs at risk (OARs). Bone shift was first assessed with a registration of the vertebrae adjacent to the lesion. Then, tumor shift was isolated with a soft tissue registration by aligning targets. IFM, combining bone and tumor shifts, was defined as the target displacement from pre to mid-treatment CBCT acquisition and was quantified in terms of anterior-posterior (AP), cranio-caudal (CC) and medio-lateral (ML) amplitudes as well as three-dimensional (3D) vector. For patients with IFM ≥ 5 mm, a post hoc dose calculation analysis was performed to assess target coverage impacts of mid-treatment CBCT-guided repositioning. Results: Ninety–seven patients, totalizing 367 fractions, were included. Mean (±SD) overall treatment time was 53:02 ± 13:08 min. Mean time from pre to midtreatment CBCT acquisition was 22:58 ± 5:33 min. Mean time to perform mid treatment CBCT scan acquisition, registrations and couch repositioning was 15:49 ± 4:14 min. Mean IFM amplitudes were 0.9 ± 1.2 mm, 0.6 ± 1.0 mm and 0.6 ± 0.8 mm in the AP, CC and ML respectively. IFM was < 3 mm and < 5 mm in all directions in respectively 315/367 (86%) and 358/367 (98%) fractions. Mean 3D IFM vector was 1.5 ± 1.4 mm (max = 8.1 mm) and was < 5 mm in 354/367 (96%). Among the 13 fractions with IFM vector ≥ 5 mm, 11/13 (85%) were dominantly induced by a tumor shift. For all these fractions, dose calculation analysis of worst-case scenario indicates that ITV coverage would have remained ≥ 95% without mid-treatment CBCT-guided patient repositioning. Conclusion: For 96% of fractions in patients immobilized with a customized BodyFIX dual vacuum bag, the IFM vector was within the 5 mm PTV margin used. Mid-treatment CBCT-guided couch repositioning did not significantly impact ITV coverage and prolonged treatment duration. Mid-treatment imaging may remain pertinent for selected patients with strict OAR dose constraints.

Intrafraction Cone Beam Computed Tomography Imaging Evaluation During Stereotactic Body Radiation Therapy for Lung Tumors and Metastatic Tumors to the Spine

Materials and Methods: 258 SABR fractions were analyzed in total, including 774 translational vectors to evaluate intra-fraction displacement: 193 fractions from 50 patients with early stage non-small cell lung tumors and 65 fractions from 15 patients with vertebral metastatic tumors included in this retrospective study. All patients underwent SBRT at our center; treatment was delivered with RapidArc with a flattened 6-MV photon beam between April 2012 and June 2013. Precise reproducible patient positioning was routinely obtained with the stereotactic double-vacuum whole body immobilization system (BodyFIX, Medical Intelligence). The vertical, longitudinal and lateral vectors were obtained by using local rigid registration of the vertebra located at the level of the region of interest on pre/mid-treatment CBCT scans. Clinical data was obtained to assess the presence of a correlation with the displacement: age, gender, Karnofsky performance status, and pulmonary function test.