Recommendations for radiotherapy quality assurance in clinical trials.

Robust quality assurance (QA) of clinical trials in radiotherapy (RT) is paramount for minimising uncertainties in treatment delivery, thereby strengthening the statistical power of the study and increasing the likelihood of accurately answering the research question. As RT techniques evolve and become more complex, establishing an appropriate QA program for a specific clinical trial becomes increasingly challenging, highlighting the importance of clear and standardised recommendations. This study provide such recommendations for Principal Investigators (PIs) to consider when planning and conducting RT Quality Assurance (RTQA) for clinical trials.

Comparison of 3-year local control using DAHANCA radiotherapy guidelines before and after implementation of five millimetres geometrical GTV to high-dose CTV margin.

Introduction: Treatment planning using a five-millimetre geometrical margin from GTV to high-dose CTV (CTV1) has been used in DAHANCA treatment centres since 2013. We aimed to evaluate changes in CTV1 volumes, local control (LC), and recurrence pattern after the implementation of five-millimetre geometrical margins nationally.

Materials And Methods: 1,948 patients with pharyngeal, and laryngeal squamous cell carcinomas completed definitive IMRT-based treatment in 2010-2012 and 2013-2015 in three centres.

High-dose loco-regional pattern of failure after primary radiotherapy in p16 positive and negative head and neck squamous cell carcinoma - A DAHANCA 19 study.

Introduction: Patients with failure after primary radiotherapy (RT) for head and neck squamous cell carcinoma (HNSCC) have a poor prognosis. This study investigates pattern of failure after primary curatively intended IMRT in a randomized controlled trial in relation to HPV/p16 status.

Material And Methods: Patients with HNSCC of the oral cavity, oropharynx (OPSCC), hypopharynx or larynx were treated with primary curative IMRT (+/-cisplatin) and concomitant nimorazole between 2007 and 12.

Tumor volume and cancer stem cell expression as prognostic markers for high-dose loco-regional failure in head and neck squamous cell carcinoma - A DAHANCA 19 study.

Background And Purpose: Reliable and accessible biomarkers for patients with Head and Neck Squamous Cell Carcinoma (HNSCC) are warranted for biologically driven radiotherapy (RT). This study aimed to investigate the prognostic value of putative cancer stem cell (CSC) markers, hypoxia, and tumor volume using loco-regional high-dose failure (HDF) as endpoint.

Materials And Methods: Tumor tissue was retrieved from patients treated with primary chemo-(C-)RT and nimorazole for HNSCC in the Danish Head and Neck Cancer Study Group (DAHANCA) 19 study.

A national repository of complete radiotherapy plans: design, Results, and experiences.

Background: Previously, many radiotherapy (RT) trials were based on a few selected dose measures. Many research questions, however, rely on access to the complete dose information. To support such access, a national RT plan database was created.

Geometric distortions in clinical MRI sequences for radiotherapy: insights gained from a multicenter investigation.

Background: As magnetic resonance imaging (MRI) becomes increasingly integrated into radiotherapy (RT) for enhanced treatment planning and adaptation, the inherent geometric distortion in acquired MR images pose a potential challenge to treatment accuracy. This study aimed to evaluate the geometric distortion levels in the clinical MRI protocols used across Danish RT centers and discuss influence of specific sequence parameters. Based on the variety in geometric performance across centers, we assess if harmonization of MRI sequences is a relevant measure.

Consistency in contouring of organs at risk by artificial intelligence vs oncologists in head and neck cancer patients.

Background: In the Danish Head and Neck Cancer Group (DAHANCA) 35 trial, patients are selected for proton treatment based on simulated reductions of Normal Tissue Complication Probability (NTCP) for proton compared to photon treatment at the referring departments. After inclusion in the trial, immobilization, scanning, contouring and planning are repeated at the national proton centre. The new contours could result in reduced expected NTCP gain of the proton plan, resulting in a loss of validity in the selection process.

Evaluation of decentralised model-based selection of head and neck cancer patients for a proton treatment study. DAHANCA 35.

Introduction: Proton treatment can potentially spare patients with H&N cancer for substantial treatment-related toxicities. The current study investigated the reproducibility of a decentralised model-based selection of patients for a proton treatment study when the selection plans were compared to the clinical treatment plans performed at the proton centre.

Methods: Sixty-three patients were selected for proton treatment in the six Danish Head and Neck Cancer (DAHANCA) centres.

Co-registration of radiotherapy planning and recurrence scans with different imaging modalities in head and neck cancer.

MRI (magnetic resonance imaging) scans are frequently used in follow-up after radiotherapy for head and neck cancer. With the overall aim of enabling MRI-based pattern of failure analysis, this study evaluated the accuracy of recurrence MRI (rMRI) deformable co-registration with planning CT (computed tomography)-scans (pCT). Uncertainty of anatomical changes between pCT and rMRI was assessed by similarity metric analyses of co-registered image structures from 19 patients.

Target coverage and local recurrences after radiotherapy for sinonasal cancer in Denmark 2008-2015. A DAHANCA study.

Purpose: The study aimed to investigate the pattern of failure and describe compromises in the definition and coverage of the target for patients treated with curatively intended radiotherapy (RT) for sinonasal cancer (SNC).

Methods And Material: Patients treated with curatively intended RT in 2008-2015 in Denmark for SNC were eligible for the retrospective cohort study. Information regarding diagnosis and treatment was retrieved from the national database of the Danish Head and Neck Cancer Group (DAHANCA).

Local recurrences after curative IMRT for HNSCC: Effect of different GTV to high-dose CTV margins.

Introduction: The aim was to analyze position of CT-verified local recurrences (LR) and local control (LC) among three centers that used different GTV to CTV1 margins.

Materials And Methods: In total, 1576 patients completing radical primary IMRT for larynx, pharynx, oral cavity HNSCC in three centers in Denmark between 2006 and 2012 were included. CT-verified LRs were analyzed as possible points of recurrence origin and compared between groups of small (0-2.

Consequences of introducing geometric GTV to CTV margin expansion in DAHANCA contouring guidelines for head and neck radiotherapy.

Background And Purpose: Defining margins around the Gross Tumour Volume (GTV) to create a Clinical Target Volume (CTV) for head and neck cancer radiotherapy has traditionally been based on presumed knowledge of anatomical routes of spread. However, using a concentric geometric expansion around the GTV may be more reproducible. The purpose of this study was to analyse the inter-observer consistency of geometric CTV delineation with adaptation for anatomical boundaries versus anatomically defined CTVs.

Implementing RapidArc into clinical routine: a comprehensive program from machine QA to TPS validation and patient QA.

Purpose: With the increased commercial availability of intensity modulated arc therapy (IMAT) comes the need for comprehensive QA programs, covering the different aspects of this newly available technology. This manuscript proposes such a program for the RapidArc (RA) (Varian Medical Systems, Palo Alto) IMAT solution.

Methods: The program was developed and tested out for a Millennium120 MLC on iX Clinacs and a HighDefinition MLC on a Novalis TX, using a variety of measurement equipment including Gafchromic film, 2D ion chamber arrays (Seven29 and StarCheck, PTW, Freiburg, Germany) with inclinometer and Octavius phantom, the Delta4 systam (ScandiDos, Uppsala, Sweden) and the portal imager (EPID).

Guiding of laser modes based on self-pumped four-wave mixing in a semiconductor amplifier.

We propose that self-pumped degenerate four-wave mixing may be used to produce novel diode laser systems where lasing is based on nonlinear guiding of the laser beams inside the active semiconductor. The fundamental process responsible for the interaction is spatial hole burning in semiconductor amplifiers. The gain and index gratings created by the modulation of the carrier density in the active gain medium lead to selective amplification of one spatial mode and suppression of all other modes.

Improvement of spatial and temporal coherence of a broad area laser diode using an external-cavity design with double grating feedback.

We demonstrate a novel technique for narrow bandwidth and highly improved lateral mode operation of a high-power broad area laser diode. The system uses simultaneous feedback from the first diffracted order and the zeroth reflected order of a diffraction grating. The two feedback paths lead to simultaneously improvement of the spectral and spatial properties of the laser diode.