Surface-guided radiation therapy for breast cancer: more precise positioning.

INTRODUCTION: Hypofractionated radiation therapy for breast cancer requires highly precise delivery through the use of image-guided radiotherapy (IGRT). Surface-guided radiation therapy (SGRT) is being increasingly used for patient positioning in breast radiotherapy. We aimed to assess the role of SGRT for verification of breast radiotherapy and the tumour bed. MATERIALS AND METHODS: Prospective study of 252 patients with early stage breast cancer. A total of 1170 determinations of daily positioning were performed. Breast surface positioning was determined with SGRT (AlignRT) and correlated with the surgical clips in the tumour bed, verified by IGRT (ExacTrac). RESULTS: SGRT improved surface matching by a mean of 5.3 points compared to conventional skin markers (98.0 vs. 92.7), a statistically significant difference (p < 0.01, Wilcoxon Test). For surface matching values > 95%, ≥ 3 clips coincided in 99.7% of the determinations and all markers coincided in 92.5%. For surface matching rates > 90%, the location of ≥ 3 clips coincided in 99.55% of determinations. CONCLUSIONS: SGRT improves patient positioning accuracy compared to skin markers. Optimal breast SGRT can accurately verify the localisation of the tumour bed, ensuring matching with ≥ 3 surgical clips. SGRT can eliminate unwanted radiation from IGRT verification systems.

Failure modes and effects analysis of total skin electron irradiation technique.

PURPOSE: Total skin electron irradiation (TSEI) is a radiotherapy technique which consists of an homogeneous body surface irradiation by electrons. This treatment requires very strict technical and dosimetric conditions, requiring the implementation of multiple controls. Recently, the Task Group 100 report of the AAPM has recommended adapting the quality assurance program of the facility to the risks of their processes. MATERIALS AND METHODS: A multidisciplinary team evaluated the potential failure modes (FMs) of every process step, regardless of the management tools applied in the installation. For every FM, occurrence (O), severity (S) and detectability (D) by consensus was evaluated, which resulted in the risk priority number (RPN), which permitted the ranking of the FMs. Subsequently, all the management tools used, related to the TSEI process, were examined and the FMs were reevaluated, to analyze the effectiveness of these tools and to propose new management tools to cover the greater risk FMs. RESULTS: 361 FMs were identified, 103 of which had RPN ≥80, initially, and 41 had S ≥ 8. Taking this into account the quality management tools FMs were reevaluated and only 30 FMs had RPN ≥80. The study of these 30 FMs emphasized that the FMs that involved greater risk were related to the diffuser screen placement and the patient's position during treatment. CONCLUSIONS: The quality assurance program of the facility has been adapted to the risk of this treatment process, following the guidelines proposed by the TG-100. However, clinical experience continually reveals new FMs, so the need for periodic risk analysis is required.

Looking for complementary alternatives to CTCAE for skin toxicity in radiotherapy: quantitative determinations.

INTRODUCTION: Radiotherapy (RT) is an essential part of the patient's treatment diagnosed with cancer. Determination of the most common RT secondary effect, the cutaneous toxicity, is usually based on visual rating scales, like Common Terminology Criteria for Adverse Events with an inherent subjectivity. The aim of this work is to perform an objective method to evaluate the radiodermatitis using a non-invasive imaging technique based on laser Doppler flowmetry (LDF). MATERIALS AND METHODS: A prospective study was performed analysing 1,824 measurements. A LDF was used to measure the cutaneous microcirculation in real time. A basal measurement was taken prior to radiotherapy treatment. To be able to observe the microcirculation changes related to the delivered dose, several sets of measurements were taken in the irradiated area along the RT treatment and in the contralateral non-irradiated area. RESULTS: A relative increase in blood flow at all measured points was found in the irradiated area. This relative increase in blood flow increases with the dose administered. In the non-irradiated contralateral area, the relative increase in blood flow is not significant and is independent of the dose administered. After treatment, a decrease in blood flow was detected with a trend towards returning to the baseline measurements. CONCLUSIONS: LDF is an objective technique that assesses early radiodermatitis. This method is useful to develop strategies to prevent onset of radiation dermatitis in patients irradiated, such as the modification and individualization of fractionation parameters of the RT. This allows the reduction of radiation morbidities and maintains patient quality of life.