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2.
Strahlenther Onkol ; 197(5): 385-395, 2021 May.
Article in English | MEDLINE | ID: mdl-33410959

ABSTRACT

BACKGROUND: In radical radiochemotherapy (RCT) of inoperable non-small-cell lung cancer (NSCLC) typical prognostic factors include T- and N-stage, while there are still conflicting data on the prognostic relevance of gross tumor volume (GTV) and particularly its changes during RCT. The NCT03055715 study of the Young DEGRO working group of the German Society of Radiation Oncology (DEGRO) evaluated the prognostic impact of GTV and its changes during RCT. METHODS: A total of 21 university centers for radiation oncology from five different European countries (Germany, Switzerland, Spain, Belgium, and Austria) participated in the study which evaluated n = 347 patients with confirmed (biopsy) inoperable NSCLC in UICC stage III A/B who received radical curative-intent RCT between 2010 and 2013. Patient and disease data were collected anonymously via electronic case report forms and entered into the multi-institutional RadPlanBio platform for central data analysis. GTV before RCT (initial planning CT, GTV1) and at 40-50 Gy (re-planning CT for radiation boost, GTV2) was delineated. Absolute GTV before/during RCT and relative GTV changes were correlated with overall survival as the primary endpoint. Hazard ratios (HR) of survival analysis were estimated by means of adjusted Cox regression models. RESULTS: GTV1 was found to have a mean of 154.4 ml (95%CI: 1.5-877) and GTV2 of 106.2 ml (95% CI: 0.5-589.5), resulting in an estimated reduction of 48.2 ml (p < 0.001). Median overall survival (OS) was 18.8 months with a median of 22.1, 20.9, and 12.6 months for patients with high, intermediate, and low GTV before RT. Considering all patients, in one survival model of overall mortality, GTV2 (2.75 (1.12-6.75, p = 0.03) was found to be a stronger survival predictor than GTV1 (1.34 (0.9-2, p > 0.05). In patients with available data on both GTV1 and GTV2, absolute GTV1 before RT was not significantly associated with survival (HR 0-69, 0.32-1.49, p > 0.05) but GTV2 significantly predicted OS in a model adjusted for age, T stage, and chemotherapy, with an HR of 3.7 (1.01-13.53, p = 0.04) per 300 ml. The absolute decrease from GTV1 to GTV2 was correlated to survival, where every decrease by 50 ml reduced the HR by 0.8 (CI 0.64-0.99, p = 0.04). There was no evidence for a survival effect of the relative change between GTV1 and GTV2. CONCLUSION: Our results indicate that independently of T stage, the re-planning GTV during RCT is a significant and superior survival predictor compared to baseline GTV before RT. Patients with a high absolute (rather than relative) change in GTV during RT show a superior survival outcome after RCT.


Subject(s)
Carcinoma, Non-Small-Cell Lung/therapy , Chemoradiotherapy , Lung Neoplasms/therapy , Tumor Burden , Adult , Aged , Aged, 80 and over , Carcinoma, Non-Small-Cell Lung/pathology , Cohort Studies , Europe , Female , Follow-Up Studies , Humans , Kaplan-Meier Estimate , Lung Neoplasms/pathology , Male , Middle Aged , Neoplasm Staging , Prognosis , Proportional Hazards Models , Radiotherapy Dosage , Retrospective Studies , Treatment Outcome , Tumor Burden/radiation effects
3.
Strahlenther Onkol ; 194(4): 293-302, 2018 04.
Article in English | MEDLINE | ID: mdl-29349604

ABSTRACT

PURPOSE: To evaluate the current situation of young radiation oncologists in Germany with regard to the contents and quality of training and level of knowledge, as well as their working conditions and professional satisfaction. METHODS: From June 2016 to February 2017, a survey was conducted by the young DEGRO (yDEGRO) using an online platform. The questionnaire consisted of 28 items examining a broad range of aspects influencing residency. There were 96 completed questionnaires RESULTS: 83% of participants stated to be very or mostly pleased with their residency training. Moderate working hours and a good colleagueship contribute to a comfortable working environment. Level of knowledge regarding the most common tumor sites (i.e. palliative indications, lung, head and neck, brain, breast, prostate) was pleasing. Radiochemotherapy embodies a cornerstone in training. Modern techniques such as intensity-modulated radiotherapy (IMRT) and stereotactic procedures are now in widespread use. Education for rare indications and center-based procedures offers room for improvement. CONCLUSION: Radiation oncology remains an attractive and versatile specialty with favorable working conditions. Continuing surveys in future years will be a valuable measuring tool to set further priorities in order to preserve and improve quality of training.


Subject(s)
Clinical Competence/standards , Education, Medical, Graduate/standards , Internship and Residency/standards , Quality Assurance, Health Care/standards , Radiation Oncology/education , Radiation Oncology/standards , Forecasting , Germany , Health Services Needs and Demand/standards , Health Services Needs and Demand/trends , Humans , Internship and Residency/trends , Job Satisfaction , Quality Assurance, Health Care/trends , Surveys and Questionnaires , Workload/standards
4.
Phys Med Biol ; 62(23): 9001-9017, 2017 Nov 13.
Article in English | MEDLINE | ID: mdl-29059054

ABSTRACT

The purpose of this study is to introduce a novel approach to incorporate patient-specific breathing variability information into 4D dose simulation of volumetric arc therapy (VMAT)-based stereotactic body radiotherapy (SBRT) of extracranial metastases. Feasibility of the approach is illustrated by application to treatment planning and motion data of lung and liver metastasis patients. The novel 4D dose simulation approach makes use of a regression-based correspondence model that allows representing patient motion variability by breathing signal-steered interpolation and extrapolation of deformable image registration motion fields. To predict the internal patient motion during treatment with only external breathing signal measurements being available, the patients' internal motion information and external breathing signals acquired during 4D CT imaging were correlated. Combining the correspondence model, patient-specific breathing signal measurements during treatment and time-resolved information about dose delivery, reconstruction of a motion variability-affected dose becomes possible. As a proof of concept, the proposed approach is illustrated by a retrospective 4D simulation of VMAT-based SBRT treatment of ten patients with 15 treated lung and liver metastases and known clinical endpoints for the individual metastases (local metastasis recurrence yes/no). Resulting 4D-simulated dose distributions were compared to motion-affected dose distributions estimated by standard 4D CT-only dose accumulation and the originally (i.e. statically) planned dose distributions by means of GTV [Formula: see text] indices (dose to 98% of the GTV volume). A potential linkage of metastasis-specific endpoints to differences between GTV [Formula: see text] indices of planned and 4D-simulated dose distributions was analyzed.


Subject(s)
Four-Dimensional Computed Tomography/methods , Liver Neoplasms/secondary , Lung Neoplasms/secondary , Neoplasm Recurrence, Local/diagnosis , Radiosurgery/methods , Radiotherapy, Intensity-Modulated/methods , Humans , Liver Neoplasms/diagnostic imaging , Liver Neoplasms/surgery , Lung Neoplasms/diagnostic imaging , Lung Neoplasms/surgery , Movement , Neoplasm Recurrence, Local/diagnostic imaging , Neoplasm Recurrence, Local/surgery , Radiotherapy Dosage , Radiotherapy Planning, Computer-Assisted/methods , Respiration , Retrospective Studies
5.
Radiologe ; 57(2): 105-110, 2017 Feb.
Article in German | MEDLINE | ID: mdl-28054139

ABSTRACT

BACKGROUND: Colorectal cancer (CRC) often presents as oligometastatic disease. Currently available intensive systemic treatment regimens, including combination chemotherapy and molecular targeted agents, result in tumor response and transient to long-term disease control in a high percentage of patients, thus raising the question of further management. Secondary resection and ablation, e.g. by surgery or radiofrequency may contribute to long-term survival and even be curative or at least allow a relevant chemotherapy-free interval. These approaches are often limited by the anatomical site, invasiveness and morbidity of the respective procedure. With stereotactic body radiotherapy (SBRT) metastases can be treated with very high efficiency in only a few sessions and achieving long-term control. OBJECTIVES: Identification of clinical studies investigating the use of SBRT for treatment of oligometastases in CRC patients. Control rates in liver and lung metastases and survival after SBRT. Toxicity and side effects of the treatment. MATERIAL AND METHODS: A literature search was carried out for prospective and retrospective studies on local SBRT. RESULTS AND CONCLUSION: The SBRT procedure has become a valid treatment option for patients with oligometastatic CRC and should also be considered in clinical practice as an alternative to surgical treatment of metastases or other local ablative techniques.


Subject(s)
Colorectal Neoplasms/epidemiology , Colorectal Neoplasms/pathology , Neoplasm Recurrence, Local/epidemiology , Neoplasm Recurrence, Local/prevention & control , Radiosurgery/statistics & numerical data , Evidence-Based Medicine , Humans , Neoplasm Metastasis , Prevalence , Risk Factors , Treatment Outcome
6.
Phys Med Biol ; 61(4): 1677-91, 2016 Feb 21.
Article in English | MEDLINE | ID: mdl-26836488

ABSTRACT

The purpose of this study was to evaluate and compare two clinical tracking systems for radiosurgery with regard to their dosimetric and geometrical accuracy in liver SBRT: the robot-based CyberKnife and the gimbal-based Vero. Both systems perform real-time tumour tracking by correlating internal tumour and external surrogate motion. CyberKnife treatment plans were delivered to a high resolution 2D detector array mounted on a 4D motion platform, with the platform simulating (a) tumour motion trajectories extracted from the corresponding CyberKnife predictor log files and (b) the tumour motion trajectories with superimposed baseline-drift. Static reference and tracked dose measurements were compared and dosimetric as well as geometrical uncertainties analyzed by a planning structure-based evaluation. For (a), γ-passing rates inside the CTV (γ-criteria of 1% / 1 mm) ranged from 95% to 100% (CyberKnife) and 98% to 100% (Vero). However, dosimetric accuracy decreases in the presence of the baseline-drift. γ-passing rates for (b) ranged from 26% to 92% and 94% to 99%, respectively; i.e. the effect was more pronounced for CyberKnife. In contrast, the Vero system led to maximum dose deviations in the OAR between +1.5 Gy to +6.0 Gy (CyberKnife: +0.5 Gy to +3.5 Gy). Potential dose shifts were interpreted as motion-induced geometrical tracking errors. Maximum observed shift ranges were -1.0 mm to +0.7 mm (lateral) /-0.6 mm to +0.1 mm (superior-inferior) for CyberKnife and -0.8 mm to +0.2 mm /-0.8 mm to +0.4 mm for Vero. These values illustrate that CyberKnife and Vero provide high precision tracking of regular breathing patterns. Even for the modified motion trajectory, the obtained dose distributions appear to be clinical acceptable with regard to literature QA γ-criteria of 3% / 3 mm.


Subject(s)
Algorithms , Gamma Rays , Liver Neoplasms/surgery , Radiation Monitoring/methods , Radiosurgery/methods , Dose-Response Relationship, Radiation , Humans , Radiation Monitoring/standards
7.
Phys Med Biol ; 53(4): 1071-85, 2008 Feb 21.
Article in English | MEDLINE | ID: mdl-18263959

ABSTRACT

An add-on multileaf collimator for electrons (eMLC) has been developed that provides computer-controlled beam collimation and isocentric dose delivery. The design parameters result from the design study by Gauer et al (2006 Phys. Med. Biol. 51 5987-6003) and were configured such that a compact and light-weight eMLC with motorized leaves can be industrially manufactured and stably mounted on a conventional linear accelerator. In the present study, the efficiency of an initial computer-controlled prototype was examined according to the design goals and the performance of energy- and intensity-modulated treatment techniques. This study concentrates on the attachment and gantry stability as well as the dosimetric characteristics of central-axis and off-axis dose, field size dependence, collimator scatter, field abutment, radiation leakage and the setting of the accelerator jaws. To provide isocentric irradiation, the eMLC can be placed either 16 or 28 cm above the isocentre through interchangeable holders. The mechanical implementation of this feature results in a maximum field displacement of less than 0.6 mm at 90 degrees and 270 degrees gantry angles. Compared to a 10 x 10 cm applicator at 6-14 MeV, the beam penumbra of the eMLC at a 16 cm collimator-to-isocentre distance is 0.8-0.4 cm greater and the depth-dose curves show a larger build-up effect. Due to the loss in energy dependence of the therapeutic range and the much lower dose output at small beam sizes, a minimum beam size of 3 x 3 cm is necessary to avoid suboptimal dose delivery. Dose output and beam symmetry are not affected by collimator scatter when the central axis is blocked. As a consequence of the broader beam penumbra, uniform dose distributions were measured in the junction region of adjacent beams at perpendicular and oblique beam incidence. However, adjacent beams with a high difference in a beam energy of 6 to 14 MeV generate cold and hot spots of approximately 15% in the abutting region. In order to improve uniformity, the energy of adjacent beams must be limited to 6 to 10 MeV and 10 to 14 MeV respectively. At the maximum available beam energy of 14 MeV, radiation leakage results mainly from the intraleaf leakage of approximately 2.5% relative dose which could be effectively eliminated at off-axis distances remote from the field edge by adjusting the jaw field size to the respective opening of the eMLC. Additionally, the interleaf and leaf-end leakage could be reduced by using a tongue-and-groove leaf shape and adjoining the leaf-ends off-axis respectively.


Subject(s)
Electrons/therapeutic use , Radiotherapy, Computer-Assisted/methods , Radiation Dosage
8.
Phys Med Biol ; 51(23): 5987-6003, 2006 Dec 07.
Article in English | MEDLINE | ID: mdl-17110765

ABSTRACT

A multileaf collimator for electrons (eMLC) has been designed that fulfils the technical requirements for providing advanced irradiation techniques with electrons. In the present work, the basic design parameters of leaf material, leaf height, leaf width and number of leaves as well as leaf overtravel and leaf shape were determined such that an eMLC with motorized leaves can be manufactured by a company specialized in MLC technology. For this purpose, a manually driven eMLC with variable source-to-collimator distance (SCD) was used to evaluate the chosen leaf specification and investigate the impact of the SCD on the off-axis dose distribution. In order to select the final SCD of the eMLC, a compromise had to be found between maximum field size, minimum beam penumbra and necessary distance between eMLC and isocentre to eliminate patient realignments during gantry rotation. As a result, the eMLC is placed according to the target position at 72 and 84 cm SCD, respectively. This feature will be achieved by interchangeable distance holders. At these SCDs, the corresponding maximum field sizes at 100 cm source-to-isocentre distance are 20 x 20 cm and 17 x 17 cm, respectively. Finally, the off-axis dose distribution at the maximum opening of the eMLC was improved by fine-tuning the settings of the accelerator jaws and introducing trimmer bars above the eMLC. Following this optimization, a prototype eMLC consisting of 2 x 24 computer-controlled brass leaves is manufactured by 3D Line Medical Systems.


Subject(s)
Electrons/therapeutic use , Radiotherapy, Conformal/instrumentation , Biophysical Phenomena , Biophysics , Equipment Design , Humans , Neoplasms/radiotherapy , Radiotherapy, Conformal/statistics & numerical data , Radiotherapy, High-Energy/instrumentation , Radiotherapy, High-Energy/statistics & numerical data
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