Strahlentherapie und Onkologie最新文献

Background: Dose variation due to changes in bowel air poses significant challenges for carbon radiotherapy in pancreatic cancer. This retrospective study evaluated a density-override optimization technique to mitigate dosimetric uncertainties caused by bowel air changes.

Materials and methods: Planning CT and cone-beam CT data from 8 patients with locally advanced pancreatic cancer undergoing stereotactic ablative radiotherapy were analyzed. Treatment simulations used a dose of 55.2 GyE in 12 fractions with a four-field setup (anterior, lateral, posterior, posterior oblique). Four density-override patterns were compared: pattern 0 (no override), pattern 1 (replacing bowel gas with water), pattern 2 (replacing the entire bowel with mean bowel HU), and pattern 3 (replacing bowel gas with mean bowel HU). Dose evaluations included fraction-wise and accumulated dose analyses, focusing on target coverage, homogeneity index, and organs at risk doses.

Results: Pattern 2 achieved the largest clinical tumor volume coverage and the fewest fractions with > 5% coverage loss for the anterior beam, followed by pattern 3. However, pattern 2 demonstrated poorer homogeneity for the lateral beam compared to patterns 1 and 3 and a higher gastrointestinal (GI) dose for the anterior beam.

Conclusion: This study evaluated the importance of density overrides to address bowel air variations. For patients where a more uniform dose is desirable or whose tumor is adjacent to the GI tract, a pattern 3 density-override should be considered.

Background: Although a cornerstone of modern cancer treatment, radiotherapy (RT) is associated with a risk of secondary cancer due to irradiation of non-target tissues. Techniques such as intensity-modulated RT (IMRT), volumetric modulated RT (VMAT), and stereotactic body RT (SBRT) provide highly conformal target dose distributions and reduce doses to nearby organs at risk (OARs), albeit at the cost of larger normal tissue volumes being irradiated with lower doses. In brachytherapy (BT), the low-value isodoses cannot be changed: they are a consequence of the inverse-square law. This study evaluates and compares the normal tissue integral doses (NTIDs) delivered by BT and modern external-beam RT (EBRT) techniques in breast and head and neck (H&N) cancer patients.

Methods: Included were the BT and IMRT plans of 34 women with early-stage breast cancer treated with interstitial high-dose-rate (HDR) BT and two groups of head and neck (H&N) patients: 38 patients with mobile tongue, floor of the mouth, and base of the tongue cancer treated definitively with interstitial HDR BT for whom VMAT treatment plans were also prepared and 20 patients with tongue and floor of the mouth tumors who received postoperative interstitial HDR BT for whom VMAT and stereotactic CyberKnife (CK, Accuray Inc., Sunnyvale, CA, USA) plans were also created. The NTIDs for three normal tissue volumes (NT_V10, NT_V5, NT_V2) and OARs were calculated and compared.

Results: Brachytherapy resulted in 39%, 32%, and 26% lower NTIDs compared to IMRT for NT_V10, NT_V5, and NT_V2, respectively, in patients with breast cancer. In H&N cancer, the NTIDs were always lower for BT compared to VMAT. The reductions in NTID achieved with BT were 45%, 36% and 27% with the same planning target volumes in BT and VMAT, and 56%, 48% and 37% with larger planning target volumes in VMAT. For CK, the NTID reductions were 54%, 49% and 41% compared to BT. In breast cases, BT resulted in a significant reduction in ipsilateral lung NTID, and in H&N cases, salivary glands NTIDs were always lower with BT than with VMAT.

Conclusion: For patients with breast and head and neck cancer, interstitial BT results in lower integral dose to normal tissue and OARs compared to modern EBRT techniques. The clinical implications require further detailed investigation.

Purpose: Needle tracking using external prediction techniques such as optical tracking is a modern approach aimed at improving implantation accuracy in gynecologic brachytherapy. This study aims to investigate the corresponding impact of needle bending in situ and to analyze needle path deviations from the intended locations occurring in our current clinical workflow that only considers ultrasound imaging without tracking.

Methods: We developed a semi-automated approach for reconstructing brachytherapy needles based on planning CTs and compared the respective accuracy to the also determined intra-observer variability of manual reconstructions. Based on this, we measured needle bending in situ for 89 patients and calculated the Euclidean distances between actual needle tips and needle tip predictions both longitudinally and laterally to the insertion direction. Furthermore, we compared actual and intended spacings between inserted needles to estimate implantation uncertainties with respect to our current clinical workflow.

Results: Our developed reconstruction featured an accuracy of 0.17 ± 0.08 mm, which was improved compared to the intra-observer variability of 0.21 ± 0.11 mm. Needle bending depended strongly on needle length and ranged from 3.6 ± 2.1 mm for 100-120 mm needles up to 7.9 ± 3.0 mm for 200-220 mm needles. Deflections in the transverse direction were substantially higher than tip deviations in the longitudinal direction. Furthermore, we found deviations from an equidistant spacing between needle paths of 1.4 ± 1.2 mm in the transverse direction.

Conclusion: Inserting brachytherapy needles can be substantially affected by transverse needle bending in situ, which should therefore be corrected for in prediction approaches such as optical tracking.

Clinical background: Cancer registry data are an essential resource for population-based oncology research and quality assurance in Germany. With the revision of the Federal Cancer Registry Data Act in 2021, for the first time, a legal basis was created for the development of a nationwide clinical cancer dataset. This registry offers new opportunities for research, particularly in radiation oncology.

Objective: This review aims to provide an overview of the current possibilities of and challenges to using German cancer registry data in radiation oncology, with a focus on data structure, missing data, access procedures, and methodological aspects for scientific research.

Methods: We examined legal frameworks, data access procedures, and the structure of the nationwide basic oncology dataset (oBDS), particularly the components relevant to radiotherapy (RT). The completeness and comprehensiveness of RT data across federal states were assessed using national registry data from the German Center for Cancer Registry Data (ZfKD) for the years 2020-2022.

Results: The cancer registries provide structured data on RT through the oBDS, including treatment intent, technique, target area, and side effects. However, significant variability in terms of completeness and reporting standards persists among federal states. Missing data rates remain high in some regions, particularly for key RT parameters such as treatment technique, the relationship to surgery, and boost application. Methodological challenges for scientific use include handling missing data, confounding, immortal time bias, and exposure misclassification.

Conclusion: Despite existing limitations, cancer registry data in Germany represent a valuable resource for real-world research in radiation oncology. They allow for large-scale population-based studies beyond the constraints of clinical trials. With improved data harmonization, methodological rigor, and future data linkages (e.g., to health insurance data), registry-based studies can contribute significantly to evidence-based decision-making and quality improvement in radiation oncology.

Purpose: Ketogenic diets (KDs) have been proposed to target glycolytic cancer metabolism and synergize with radio- and chemotherapy. We herein report survival outcomes of rectal and head and neck cancer (HNC) patients who followed a KD during radio(chemo)therapy.

Methods: Thirty-five patients on a KD during radiotherapy and 46 patients on a standard diet were prospectively followed. Overall (OS), progression-free (PFS), and locoregional recurrence-free survival (RFS) were analyzed with the Kaplan-Meier method and by computing restricted mean survival times. Acute radiotherapy-induced side effects were compared using Fisher's exact test. In an exploratory analysis, patients in the KD group were matched to control patients with propensity score matching, and survival analysis was performed.

Results: Median follow-up was 77.4 (range 12.1-107.9; HNC) and 71.3 (1.5-127.1) months (rectal cancer), respectively. There were no significant differences in any survival outcome between the KD and control groups in either cohort. A numerically longer restricted mean RFS time for HNC patients did not reach the statistical significance threshold (KD: 100.5 months, 0 events; control group: 87.3 ± 7.0 months, 3 events; p = 0.059). In the propensity score-matched HNC sample, patients on a KD exhibited numerically longer OS (log-rank test: p = 0.084) and RFS (p = 0.064); however, these differences were not statistically significant. Acute skin toxicity was less severe in HNC patients on a KD (p = 0.063), which became significant in intention-to-treat analysis (p = 0.0495); all other acute toxicities were without significant differences between the groups.

Conclusion: Our analysis failed to detect a significant survival benefit of a KD during radio(chemo)therapy in HNC and rectal cancer patients, but provides further evidence for the safety of this approach.

Purpose: Ensuring reproducible treatments and therapeutic temperature rises is pivotal for wider clinical application of hyperthermia. We propose a fast automated quality assurance (QA) procedure using E‑field measurements for relative specific absorption rate (SAR) applicator characterization, with a similar workflow to radiotherapy dosimetry.

Methods: Our procedure was demonstrated for 434 MHz superficial contact flexible microstrip applicators (CFMA) with similar antennas and geometry to the ALBA ON 4000D system. Applicators were placed on a liquid saline phantom. A Cartesian robot performed E‑field measurements moving E‑field sensors through the phantom. We analysed the influence of spatial resolution on effective field size (EFS) measurements. Using volume measurements, we established effective penetration depth (EPD) variation across the aperture. We evaluated repeatability, measuring central planes on eight different days. Applicators/phantoms were characterized with flat and curved setups, using standard clinical and more excessive bolus thicknesses.

Results: Procedures take ~40 min per setup condition. One-centimetre spatial resolution appears sufficient for QA. EPD showed errors < 5% when determined from high-SAR regions (~80-90% of the maximum). The EFS and EPD variability between different days was < 5%. Increasing EPD and decreasing EFS with increasing curvature was observed when using the clinical bolus thickness, with more homogeneous SAR distributions for curved than for flat setups. Excessive bolus thickness resulted in irregular SAR distributions and larger EFS and EPD variations.

Conclusion: The proposed QA procedure is characterized by fast, practical and reproducible measurements that are suitable for efficiently evaluating various setup conditions. This flexible workflow can also be used with other radiative hyperthermia systems.

Background: In Germany, the development of evidence based medical guidelines is overseen by the Association of the Scientific Medical Societies (AWMF). Ensuring balanced representation across medical specialties and genders is essential for generating comprehensive, equitable, and unbiased treatment recommendations. This study evaluates the involvement of radiation oncology (RO) specialists and assesses gender representation within the panels of German oncological guidelines.

Methods: We analysed all oncological guidelines in the AWMF registry (n = 93/820). Data were collected from AWMF's registry, the German Society for Radiation Oncology (DEGRO) website, and affiliated organizations including the Working Group for Radiation Oncology (ARO) and the Professional Association of German Radiation Oncologists (BVDST). Gender distribution, academic qualifications, and participation rates were analysed.

Results: Of 93 oncological AWMF guidelines, RO panel members participated in 71 (76.3%), with particularly high representation in S3 (highest standard of quality and reliability) guidelines (92.5%). A total of 2795 panelists were represented in 85 analysable oncological guidelines, with 28.3% being female. Among the 255 RO panelists, the proportion of women is significantly higher with 34.5% (p < 0.05), with varying distribution across organizations: DEGRO 38.6%, ARO 31.7%, and BVDST 28.2%. Academic qualifications regarding all panelists differed significantly by gender (p < 0.001) with a high proportion of professors being male (81.3%), while women were disproportionately represented among those no academic title (62.6%).

Conclusions: RO demonstrates strong representation in German oncological guideline development, in contrast to international trends where the specialty is frequently underrepresented. Nonetheless, consistent with patterns observed across other medical disciplines and healthcare systems, gender disparities remain evident: women constitute roughly one-third of overall panel members. These findings establish an important reference point for tracking future progress toward achieving gender equity in the formulation of oncological guidelines.