Radiotherapy and Oncology最新文献

Background and purpose: Postoperative target delineation after reconstructive surgery in head and neck cancer (HNC) is heterogeneous; whether to include the flap or focus on the native tissue-flap junction is debated. We quantified patterns of relapse relative to flaps and summarized practice, toxicity and function.

Materials and methods: in the retrospective XFLAP1 cohort (2018-2023), patients with HNC underwent tumor resection with flap reconstruction and postoperative radiotherapy (PORT) ± concurrent chemotherapy. Competing-risks (Fine-Gray) estimated locoregional relapse (LRR) and metastases; overall survival (OS) used Kaplan-Meier. Flaps were contoured a posteriori on planning CTs, when available.

Results: Of 355 patients across eight centres, free flaps were used in 239 (67%) and regional pedicled flaps in 69 (33%). The entire flap body was encompassed in the CTVs in 66% of plans; median flap-body dose was 65.3 Gy and pedicle Dmax 67.5 Gy for the delineated flaps (N = 153). Median follow-up was 32.9 months, 120/355 (34%) patients relapsed, including 68 (19%) LRR and 71 (20%) metastases. Median time to LRR was 7.35 months; only 3 (1%) of relapses arose within the flap body. Two-year cumulative incidence was 15.8% for LRR and 16.7% for metastases; two-year OS was 74.6%. On multivariable analysis, pN2-3 predicted metastases; LRR, metastases, and ECOG ≥ 1 were associated with worse OS.

Conclusions: relapses in the flap-body epicentre were rare; most local failures involved the native tissue-flap junction or non-flap sites. These data support junction-focused CTVs with reduced emphasis of the flap body to limit morbidity, pending prospective validation.

Introduction: Intensity Modulated Radiotherapy (IMRT) and Image Guided Radiotherapy (IGRT) have become an integral part of standard care for rectal cancer, but evidence-based detailed guidance is lacking to support its clinical implementation and use. This European SocieTy for Radiotherapy and Oncology (ESTRO) technical guideline aimed to assess the available evidence and provide recommendations for their use in rectal cancer treatment.

Materials and methods: The ESTRO Lower Gastrointestinal (GI) Cancer guidelines subcommittee formed a writing panel to address key questions (KQs) on the application of IMRT and IGRT in rectal cancer management. The panel conducted a literature review and where evidence was insufficient, expert consensus was used.

Results: The writing panel (2 RTTs, 2 medical physics experts, 3 radiation oncologists) identified 14 KQs. Recommendations were based on low to moderate evidence and/or expert consensus. Supine positioning is preferred for patient comfort and stability. Comfortable full bladder should be used. For OAR delineation and dose optimization, mandatory (Bladder, Bowel Cavity, Femoral Heads) and optional OAR were defined. Auto-delineation is supported for OAR and can be considered for target volumes. Dose metrics for minimizing gastrointestinal and genitourinary toxicity were identified. Auto-planning tools and MR-only workflows are feasible, both require proper QA. Uncertainties from setup and target volume shape variations must be accounted for with appropriately defined margins. Daily volumetric image guidance is recommended for treatment verification.

Conclusion: This ESTRO technical guideline for the use of IMRT and IGRT for rectal cancer was developed to support development and implementation into clinics.

Purpose: Assess consistency of end-to-end dosimetry audits used by six Global Quality Assurance of Radiation Therapy Clinical Trials Harmonization Group (GHG) member organizations to harmonise audits and reduce audit overlap in multinational trials while maintaining quality.

Methods: Prior work developed and validated 16 head and neck reference plans, based on established international dosimetry audits for intensity modulated radiotherapy treatments. Realistic modifications, developed from reported variations in clinical practice, were introduced into nine copies of each plan, generating 144 modified plans. These plans were grouped as acceptable (should pass) and unacceptable (should fail) using plan assessment metrics and action limits on CTV_mean, CTV_D95, and OAR_D0.03cc. In the current work, each GHG audit system measured the error-free reference plans on its own phantom using its standard workflow. The measured error-free plans were then compared to the dose calculations of the modified plans. Outcomes were expressed as pass/fail, which were then compared to the "should pass/should fail" benchmark to determine the sensitivity and specificity of each system. An optimal action limit was determined for each audit system to achieve a common sensitivity across all audit systems.

Results: All audit systems reliably identified failing plans (sensitivity 0.92-1.0; specificity 0.40-0.91) with 5% ΔCTV_mean assessment action thresholds. Adjusting the action limit revealed that each audit system was tuned to detect different error thresholds (3.3% - 5.7%). Changing audit system action limits specificity, while preserving system sensitivity.

Conclusion: The comparably high sensitivity across all audit systems could allow harmonising of dosimetry audits for clinical trials on an international scale based on sensitivity alone. Future work harmonising specificity would help streamline credentialing for international clinical trials.

Background and purpose: Anatomical landmarks are often used to assess the quality of a deformable image registration (DIR) between two scans. However, such landmarks are manually placed on both scans, which is prone to observer variability. We analysed the interobserver variability of the placement of corresponding landmarks on pelvic scans, to provide context for DIR validation studies that use landmarks as a reference.

Material and methods: Pelvic CT and MRI scans of nine cervical cancer patients were distributed to 17 observers. Three annotation settings were considered, each including scan pairs of five patients: CT-CT (13 observers), MRI-CT (eight observers), and MRI-MRI (eight observers). The observer group consisted of 15 RTTs professionally trained in working with scans of the given modality, and two fourth-year Ph.D. students in the domain. During annotation, observers received the same reference scan of each patient with 23 anatomically relevant, pre-annotated landmarks, and were asked to annotate the corresponding location of each reference landmark on a second scan of the same patient. To quantify the interobserver variability between different landmark placements on the same patient scan, their geometric median was used to approximate the true corresponding landmark location.

Results: Placements of landmarks on soft tissue for all patients deviated from their geometric median by a median 3D Euclidean distance of 3.0 mm (CT-CT), 5.6 mm (MRI-CT), and 2.6 mm (MRI-MRI). On bony anatomy, variability was significantly lower. Overall, variability was positively correlated with the deformation magnitude in the region.

Conclusions: There is large interobserver variability in anatomical landmark placements on pelvic CT and MRI scans. Variability frequently exceeds voxel size, challenging the AAPM guideline recommending landmark-based DIR quality assessment.