Implementation of radiation therapist cylinder insertion for vaginal vault brachytherapy.

Vaginal vault brachytherapy is a common treatment for endometrial cancer. Historically, applicator insertion has been the domain of a radiation oncologist (RO). This commentary outlines a project to improve efficiency and workforce utilisation by introducing a competency framework and training module allowing entitled radiation therapists to perform single-channel cylinder applicator insertions and treatment delivery under RO supervision for fraction one and without supervision for subsequent fractions. The rationale, relevant regulations, implementation process and barriers are explored.

Dosimetric comparison of surface mould HDR brachytherapy with VMAT.

INTRODUCTION: The aim of this study was to investigate the dosimetric differences between surface mould high-dose-rate (HDR) brachytherapy and external beam volumetric-modulated arc therapy (VMAT) for two treatment sites. METHODS: Previously treated HDR brachytherapy surface mould scalp (n = 4) and lower leg (n = 3) treatments were retrospectively analysed. The VMAT plans were optimised using an additional 3-mm setup margin on the clinical target volume (CTV) of the previously treated HDR plans. The HDR plans were calculated and normalised using the TG-43 formalism and recalculated with Acuros BV (AC). RESULTS: On average, the mean brain and normal tissue doses were reduced by 44.8% and 27.4% for scalp and lower leg VMAT cases, respectively, when compared to AC calculated HDR plans. For VMAT plans, the average dose to a 1-mm thick skin structure deep to the target volume was not any lower than that in AC HDR plans. On average, the CTV coverage was 13.8% and 9.6% lower for scalp cases with AC dose calculation than with TG-43 and 8.3% and 5.3% lower for lower leg cases if 0- or 1-cm backscatter material was applied above the catheters, respectively. CONCLUSIONS: VMAT is a feasible treatment option in the case of extensive skin malignancies of the scalp and lower leg. Uncertainties related to delivered dose with HDR brachytherapy when using the TG-43 dose calculation model or possible air gaps between the mould and skin favour the use of VMAT. The potential soft tissue deformation needs to be considered if VMAT is used.

The validity of Acuros BV and TG-43 for high-dose-rate brachytherapy superficial mold treatments.

PURPOSE: The purpose of this work is to validate the Acuros BV dose calculation algorithm for high-dose-rate (HDR) brachytherapy superficial mold treatments in the absence of full scatter conditions and compare this with TG-43 dose calculations. We also investigate the impact of additional back scatter material (bolus) applied above surface molds to the dose distributions under the mold. METHODS AND MATERIALS: The absorbed dose at various depths was compared for simulations performed using either TG-43 or Acuros BV dose calculations. Parameter variations included treatment area, thickness of the bolus, and surface shape (flat or spherical). Film measurements were carried out in a flat phantom. RESULTS: Acuros BV calculations and film measurements agreed within 1.5% but were up to 15% lower than TG-43 dose calculations when no bolus was applied above the treatment catheters. The difference in dose at the prescription depth (1 cm below the central catheter) increased with increasing treatment area: 3.3% difference for a 3 × 3.5 cm2 source loading area, 7.4% for 8 × 9 cm2, and 13.4% for 18 × 19 cm2. The dose overestimation of the TG-43 model decreased when bolus was added above the treatment catheters. CONCLUSIONS: The TG-43 dosimetry formalism cannot model surface mold treatments in the absence of full scatter conditions within 5% for loading areas larger than approximately 5 × 5 cm2. The TG-43 model results in an overestimation of the delivered dose, which increases with treatment area. This confirms the need for model-based dose calculation algorithms as discussed in TG-186.

Intracavitary vaginal brachytherapy using a custom balloon applicator.

A custom balloon applicator was created to deliver intracavitary high-dose-rate brachytherapy to a patient with a superficial vaginal cancer. The patient was unable to be treated conventionally due to an extremely narrow introitus that prevented the introduction of a conventional cylinder applicator. The custom applicator was constructed by inserting a straight titanium tandem applicator through the drainage lumen of a Foley catheter. The applicator was inserted and the catheter balloon was inflated when positioned at the vaginal apex. Three brachytherapy treatments were performed using this technique. Individual balloon eccentricities resulted in small radial tandem offsets within the balloon. This phenomenon was exploited by orientating the tandem offset in the direction of the target volume. Acceptable dosimetry was achieved for all fractions and the procedure was very well tolerated. The custom applicator was a viable solution that was safely developed in a short time frame using equipment readily available in our department.

Prophylactic use of Mepitel Film prevents radiation-induced moist desquamation in an intra-patient randomised controlled clinical trial of 78 breast cancer patients.

PURPOSE: Safetac-based soft silicone dressings used in a management setting decrease the severity of radiation-induced acute skin reactions but do not affect moist desquamation rates. Here we investigate the prophylactic use of another Safetac product, Mepitel Film, on moist desquamation rates. MATERIAL AND METHODS: A total of 80 breast cancer patients receiving radiation therapy were recruited between October 2012 and April 2013; 78 participants contributed data for analysis. Lateral and medial halves of the skin areas to be irradiated were randomised to Mepitel Film or aqueous cream; skin dose was measured using thermoluminescent dosimeters; skin reaction severity was assessed using RISRAS and RTOG scales. RESULTS: Overall skin reaction severity was reduced by 92% (p<0.0001) in favour of Mepitel Film (RISRAS). All patients developed some form of reaction in cream-treated skin which progressed to moist desquamation in 26% of patients (RTOG grades I: 28%; IIA: 46%; IIB: 18%; III: 8%). Only 44% of patients had a skin reaction under the Film, which did not progress to moist desquamation in any of the patients (RTOG grades I: 36%; IIA: 8%). CONCLUSIONS: Mepitel Film completely prevented moist desquamation and reduced skin reaction severity by 92% when used prophylactically in our cohort.