Errors detected during physics plan review for external beam radiotherapy.

Background and purpose: Risk management in radiotherapy is of high importance. There is not much data published on errors occurring in the treatment planning process of external beam techniques. The aim of this study was to investigate errors occurring during physics plan review in external beam radiotherapy. Materials and methods: Over a period of 14 months errors observed during the physical review process are reported. The errors were grouped and evaluated regarding treatment machine, technique, and treatment site. In addition, a correlation between frequency of errors and staff shortage was analyzed. Results: Subgroups of grave errors (g-errors) and slight errors (s-errors) were defined to consider the different impact on the patient and clinical workflow of the errors. In 1056 plans reviewed, 110 errors (41 g-errors, 69 s-errors) were detected. The most common g-errors and s-errors were "Wrong gantry angle at setup field" (n = 19) and "Wrong field label" (n = 24), respectively. A correlation of number of errors and treatment machine, technique, or anatomical site could not be found. No correlation between staff shortage and number of errors was observed. Conclusions: The process of reviewing treatment plans is a relevant topic to consider in risk analysis of the radiotherapy workflow. The review process could be improved by enhancements in the treatment planning systems, use of digital dose prescription, and treatment planning templates.

End-to-end test for computed tomography-based high-dose-rate brachytherapy.

PURPOSE: One of the important developments in brachytherapy in recent years has been the clinical implementation of complex modern technical procedures. Today, 3D-imaging has become the standard procedure and it is used for contouring and precise position determination and reconstruction of used brachytherapy applicators. Treatment planning is performed on the basis of these imaging methods, followed by data transfer to the afterloading device. Therefore, checking the entire treatment chain is of high importance. In this work, we describe an end-to-end test for computed tomography (CT)-based brachytherapy with an high-dose-rate (HDR) afterloading device, which fulfills the recommendation of the German radiation-protection-commission. MATERIAL AND METHODS: The treatment chain consists of a SOMATOM S64 CT scanner (Siemens Medical), the treatment planning system (TPS) BrachyVision v.13.7 (VMS), which utilizes the calculation formalism TG-43 and the Acuros algorithm v. 1.5.0 (VMS) as well as GammaMedplus HDR afterloader (VMS) using an Ir-192 source. Measurement setups for common brachytherapy applicators are defined in a water phantom, and the required PMMA applicator holders are developed. These setups are scanned with the CT and the data is imported into the TPS. Computed TPS reference dose values for significant points located on the side of the applicator are compared with dose measurements performed with a PinPoint 3D chamber 31016 (PTW Freiburg). RESULTS: The deviations for the end-to-end test between computed and measured values are shown to be ≤ 5%, when using an implant needle or vaginal cylinder. Furthermore, it can be demonstrated that the test procedure provides reproducible results, while repositioning the applicators without carrying out a new CT-scan. CONCLUSIONS: The end-to-end test presented allows a practice-oriented realization for checking the whole treatment chain for HDR afterloading technique and CT-imaging. The presented phantom seems feasible for performing periodic system checks as well as to verify newly introduced brachytherapy techniques with sufficient accuracy.

Targeting hypoxia to overcome radiation resistance in head & neck cancers: real challenge or clinical fairytale?

INTRODUCTION: Tumor hypoxia is a major cause for failure of therapy in patients with inoperable head and neck cancers. AREAS COVERED: Various anti-hypoxic treatment strategies (e.g. hyperbaric oxygenation, hypoxic cell sensitizers) have been tested in clinical trials in head and neck cancer over the past 30 years and have shown modest improvements in combination with radiotherapy in meta-analyses. Anemia worsens tumor hypoxia, but anemia correction had no significant effect. New approaches (e.g. anti-HIF-directed molecular therapies) have just entered early clinical studies and data are lacking. Expert commentary: A new attractive and promising approach derives from recent advances in imaging and radiotherapy delivery. Progress in imaging of hypoxia (e.g. by positron emission tomography) can select patients for specific therapies and may, in particular, facilitate anti-hypoxia-directed radiotherapy which has become feasible with advanced radiotherapy techniques (IMRT with 'dose-painting'). The combination of both methods may offer a powerful tool for effective targeting of hypoxia in the near future.