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PurposeTo evaluate the feasibility of acute and chronic toxicity in patients suitable for accelerated partial breast irradiation (APBI) in a single 18 Gy fraction with multicatheter high-dose-rate (HDR) brachytherapy, as well as cosmetic and oncological outcomes.Material and methodsBetween September 2014 and March 2016, twenty consecutive patients with low-risk invasive and ductal carcinoma in situ were treated with interstitial multicatheter HDR brachytherapy in a single 18 Gy fraction.ResultsMedian age was 63.5 years (range, 51-79). Acute toxicity was observed in seven patients, while the pain during following days and hematoma were seen in four patients. With a median follow-up of 24 months, late toxicity was found in one patient with fat necrosis g2 and fibrosis g2 in another patient. The overall survival (OS) and locoregional control (LC) was 100%. Disease-free survival (DFS) and distant control was 95%. Good to excellent cosmetic outcomes were noted in 80% of patients and fair in 4 patients (20%).ConclusionsThis is the first report in the medical literature that focuses on feasibility and acute and chronic toxicity, with a median follow-up of 24 months (range, 20-40). The protocol is viable and convenient. However, a longer follow-up is needed to know chronic toxicity and oncologic outcomes.

Purpose: The objective of this study was to characterize the Best Medical Canada microMOSFET detectors for their application in in vivo dosimetry for high-dose-rate brachytherapy (HDRBT) with 192 Ir. We also developed a mathematical model to correct dependencies under the measurement conditions of these detectors. Methods: We analyzed the linearity, reproducibility, and interdetector variability and studied the microMOSFET response dependence on temperature, source-detector distance, and angular orientation of the receptor with respect to the source. The correction model was applied to 19 measurements corresponding to five simulated treatments in a custom phantom specifically designed for this purpose. Results: The detectors (high bias applied in all measurements) showed excellent linearity up to 160 Gy. The response dependence on source-detector distance varied by (8.65 AE 0.06)% (k = 1) for distances between 1 and 7 cm, and the variation with temperature was (2.24 AE 0.05)% (k = 1) between 294 and 310 K. The response difference due to angular dependence can reach (10.3 AE 1.3)% (k = 1). For the set of measurements analyzed, regarding angular dependences, the mean difference between administered and measured doses was À4.17% (standard deviation of 3.4%); after application of the proposed correction model, the mean difference was À0.1% (standard deviation of 2.2%). For the treatments analyzed, the average difference between calculations and measures was 4.7% when only the calibration coefficient was used, but it is reduced to 0.9% when the correction model is applied. Conclusion: Important response dependencies of microMOSFET detectors used for in vivo dosimetry in HDRBT treatments, especially the angular dependence, can be adequately characterized by a correction model that increases the accuracy of this system in clinical applications.

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