Robert Doucet

Predictive Parameters of CyberKnife Fiducial-less (XSight Lung) Applicability for Treatment of Early Non-Small Cell Lung Cancer: A Single-Center Experience

PURPOSE To determine which parameters allow for CyberKnife fiducial-less tumor tracking in stereotactic body radiation therapy (SBRT) for early-stage non-small cell lung cancer. METHODS AND MATERIALS A total of 133 lung SBRT patients were preselected for direct soft-tissue tracking based on manufacturer recommendations (peripherally located tumors ≥1.5 cm with a dense appearance) and staff experience. Patients underwent a tumor visualization test to verify adequate detection by the tracking system (orthogonal radiographs). An analysis of potential predictors of successful tumor tracking was conducted looking at: tumor stage, size, histology, tumor projection on the vertebral column or mediastinum, distance to the diaphragm, lung-to-soft tissue ratio, and patient body mass index. RESULTS Tumor visualization was satisfactory for 88 patients (66%) and unsatisfactory for 45 patients (34%). Median time to treatment start was 6 days in the success group (range, 2-18 days) and 15 days (range, 3-63 days) in the failure group. A stage T2 (P=.04), larger tumor size (volume of 15.3 cm(3) vs 6.5 cm(3) in success and failure group, respectively) (P<.0001), and higher tumor density (0.86 g/cm(3) vs 0.79 g/cm(3)) were predictive of adequate detection. There was a 63% decrease in failure risk with every 1-cm increase in maximum tumor dimension (relative risk for failure = 0.37, CI=0.23-0.60, P=.001). A diameter of 3.6 cm predicted a success probability of 80%. Histology, lung-to-soft tissue ratio, distance to diaphragm, patients body mass index, and tumor projection on vertebral column and mediastinum were not found to be predictive of success. CONCLUSIONS Tumor size, volume, and density were the most predictive factors of a successful XSight Lung tumor tracking. Tumors >3.5 cm have ≥80% chance of being adequately visualized and therefore should all be considered for direct tumor tracking.

Excellent Cancer Outcomes Following Patient-adapted Robotic Lung SBRT But a Case for Caution in Idiopathic Pulmonary Fibrosis

The aim of this study is to report outcomes and prognostic factors for early stage non-small cell lung cancer treated with patient-adapted Cyberknife stereotactic body radiotherapy. A retrospective analysis of 150 patients with T1-2N0 non-small cell lung cancer treated with stereotactic body radiotherapy was conducted. An algorithm based on tumor and patient’s characteristics was used to orient patients towards soft tissue (Xsight Lung), fiducials or adjacent bone (Xsight Spine) tracking. Median biological effective dose without correction for tissue inhomogeneities was 180 Gy10 for peripheral tumors and 113 Gy10 for central tumors. Median follow-up was 22 months. Actuarial 2 years local control, overall survival and disease-specific survival were respectively 96%, 87% and 95%. Every 1 cm increase in tumor diameter was associated with a relative risk for regional or distant relapse of 2 (95%CI = 1.2-3.6, p = 0.009). With doses ≥132 Gy10 and <132 Gy10, local control was 98% vs. 82% (p = 0.07), disease-specific survival 97% vs. 78% (p = 0.02) and overall survival 93% vs. 76% (p = 0.01), respectively. Better disease-specific survival and a trend for better overall survival was observed for peripheral vs. central tumors (96% vs. 79%, p = 0.05 and 92% vs. 74%, p = 0.08, respectively). A higher Charlson comordibity score (≥4) predicted lower overall survival (79% vs. 98%, p = 0.01). Toxicities included 3 patients with idiopathic pulmonary fibrosis who developed grade 5 pneumonitis and 2 patients with grade 3 pneumonitis. We therefore report excellent local control and disease-specific survival following patient-adapted Cyberknife lung stereotactic body radiotherapy. Although toxicities were in general minimal, patients with pulmonary fibrosis might be at greater risk of severe complications. Small size, peripheral location, dose ≥ 132 Gy10 and a low Charlson co-morbidity score seem to be associated with better outcomes.

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.

Bone marrow-sparing intensity-modulated radiation therapy for Stage I seminoma

Abstract Background. A direct association between radiotherapy dose, side-effects and secondary cancers has been described in patients with seminoma. A treatment planning study was performed in order to compare computed tomography-based traditional radiotherapy (CT-tRT) versus bone marrow-sparing intensity-modulated radiation therapy (BMS-IMRT) in patients with Stage I seminoma. Material and methods. We optimized in 10 patients a CT-tRT and a BMS-IMRT treatment plan to deliver 20 Gy to the para-aortic nodes. CT-tRT and IMRT consisted of anteroposterior-posterioranterior parallel-opposed and seven non-opposed coplanar fields using 16 and 6-MV photon energies, respectively. Dose-Volume Histograms for clinical target volume (CTV), planning target volume (PTV) and organs at risk (OARs) were compared for both techniques using Wilcoxon matched-pair signed rank-test. Results. Dmean to CTV and PTV were similar for both techniques, even if CT-tRT showed a slightly improved target coverage in terms of PTV-D95% (19.7 vs. 19.5 Gy, p = 0.005) and PTV-V95% (100 vs. 99.7%, p = 0.011) compared to BMS-IMRT. BMS-IMRT resulted in a significant reduction (5.2 Gy, p = 0.005) in the Dmean to the active bone marrow (ABM). The V100% and V75% of the OARs were reduced with BMS-IMRT by: ABM-V100% = 51.7% and ABM-V75% = 42.3%; bowel-V100% = 15.7% and bowel-V75% = 16.8%; stomach-V100% = 22% and stomach-V75% = 27.7%; pancreas-V100% = 37.1% and pancreas-V75% = 35.9% (p = 0.005 for all variables). Conclusions. BMS-IMRT reduces markedly the dose to the OARs compared to CT-tRT. This should translate into a reduction in acute and long-term toxicity, as well as into the risk of secondary solid and hematological cancers.

Long-term results of radiosurgery for cerebral arteriovenous malformations.

BACKGROUND Stereotactic radiosurgery (SRS) is known to safely result in a high obliteration rate for small and medium sized arteriovenous malformations (AVM). OBJECTIVE To evaluate the long-term outcome of patients treated with SRS, with special emphasis given to obliteration and toxicity rates. METHODS We performed a review of 43 cerebral AVM patients, treated from 1998 to 2008 with a single SRS dose ranging from 21-25 Gy. Of these, 37 had a minimal follow-up of one year. Medical files were reviewed to assess patient and AVM characteristics, the SRS treatment, therapy prior to SRS, the obliteration rate and toxicities. Whenever necessary, outcome data was supplemented by telephone interviews with the patient or treating physician. RESULTS AVM size was ≥3cm in diameter in 21% of patients. Five patients (11.6%) underwent surgery prior to SRS and 31 patients (72.1%) received one or more embolizations prior to SRS. Of the patients followed with angiography ≥1 year post-SRS, 89% (33/37) had a complete obliteration of the nidus, after a median time of 24.7 months post-treatment. Embolization prior to SRS was not predictive of outcome. One patient suffered a non-fatal haemorrhage between treatment and obliteration. The rate of symptomatic radiation-induced radiological changes was 8.1%. CONCLUSION Our study shows both obliteration and complication rates in the upper limit of those reported in the literature. SRS seems an attractive treatment option for small AVMs. Unlike other reports, the prior use of embolization did not impact negatively on obliteration rates.

A dosimetric parameter to limit chest wall toxicity in SABR of NSCLC

OBJECTIVE Chest wall (CW) toxicity (rib fracture and/or pain) is a recognized complication of stereotactic ablative radiotherapy (SABR) for non-small-cell lung cancer. The aim of this study was to evaluate the frequency of CW toxicity following SABR and to propose a new dosimetric parameter. METHODS We reviewed the charts and SABR plans from patients treated for T1-T2N0 peripheral non-small-cell lung cancer between 2009 and 2015. The CW structure was created through a 3-cm expansion of the lung. The median dose delivered to the planning target volume was 60 Gy. SABR was delivered in three fractions for patients with CW V30 < 30 cm3. If the CW V30 exceeded 30 cm3, five fractions were used, and the plan was optimized based on CW V37 (biologically equivalent to the V30 of three-fraction plans). RESULTS In 6 years, 361 lesions from 356 patients were treated (3 fractions: 297; 5 fractions: 64). The median follow-up was 16 months. 23 patients (6.5%) developed CW toxicity after a median time of 10 months following treatment. The mean CW V30/V37 was 21 cm3 for patients with CW toxicity and 17 cm3 for patients without toxicity (p < 0.05). The 2-year local control and the CW toxicity rates were similar, whether patients received three or five fractions (97% vs 96% and 7% vs 5%). CONCLUSION When the CW V30 is >30 cm3, altered fractionation combined with V37 optimization can limit CW toxicity. Advances in knowledge: The CW V37 is a suggested dosimetric parameter adapted to fractionation that may potentially limit CW toxicity after lung SABR.

Reproducibility of a Noninvasive System for Eye Positioning and Monitoring in Stereotactic Radiotherapy of Ocular Melanoma

Purpose: Our preferred treatment for juxtapapillary choroidal melanoma is stereotactic radiotherapy. We aim to describe our immobilization system and quantify its reproducibility. Materials and Methods: Patients were identified in our radiosurgery database. Patients were imaged at computed tomography simulator with an in-house system which allows visual monitoring of the eye as the patient fixates a small target. All patients were reimaged at least once prior to and/or during radiotherapy. The patients were treated on the CyberKnife system, 60 Gy in 10 daily fractions, using skull tracking in conjunction with our visual monitoring system. In order to quantify the reproducibility of the eye immobilization system, computed tomography scans were coregistered using rigid 6-dimensional skull registration. Using the coregistered scans, x, y, and z displacements of the lens/optic nerve insertion were measured. From these displacements, 3-dimensional vectors were calculated. Results: Thirty-four patients were treated from October 2010 to September 2015. Thirty-nine coregistrations were performed using 73 scans (2-3 scans per patient). The mean displacements of lens and optic nerve insertion were 0.1 and 0.0 mm. The median 3-dimensional displacements (absolute value) of lens and nerve insertion were 0.8 and 0.7 mm (standard deviation: 0.5 and 0.6 mm). Ninety-eight percent of 3-dimensional displacements were below 2 mm (maximum 2.4 mm). The calculated planning target volume (PTV) margins were 0.8, 1.4, and 1.5 mm in the anterior–posterior, craniocaudal, and right–left axes, respectively. Following this analysis, no further changes have been applied to our planning margin of 2 to 2.5 mm as it is also meant to account for uncertainties in magnetic resonance imaging to computed tomography registration, skull tracking, and also contouring variability. Conclusion: We have found our stereotactic eye immobilization system to be highly reproducible (<1 mm) and free of systematic error.

Larynx motion considerations in partial larynx volumetric modulated arc therapy for early glottic cancer

To assess laryngeal motion in early glottic cancer in order to determine safe margins for partial larynx volumetric modulated arc therapy (PL‐VMAT), and to quantify dosimetric advantages of PL‐VMAT.

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.