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Rectum and bladder volumes play an important role in the dose distribution reproducibility in prostate cancer adenocarcinoma (PCa) radiotherapy, especially for particle therapy, where density variation can strongly affect the dose distribution. We investigated the reliability and reproducibility of our image-guided radiotherapy (IGRT) and treatment planning protocol for carbon ion radiotherapy (CIRT) within the phase II mixed beam study (AIRC IG 14300) for the treatment of high-risk PCa. In order to calculate the daily dose distribution, a set of synthetic computed tomography (sCT) images was generated from the cone beam computed tomography (CBCT) images acquired in each treatment session. Planning target volume (PTV) together with rectum and bladder volume variation was evaluated with sCT dose-volume histogram (DVH) metric deviations from the planning values. The correlations between the bladder and rectum volumes, and the corresponding DVH metrics, were also assessed. No significant difference in the bladder, rectum, and PTV median volumes between the planning computed tomography (pCT) and the sCT was found. In addition, no significant difference was assessed when comparing the average DVHs and median DVH metrics between pCT and sCT. Dose deviations determined by bladder and rectum filling variations demonstrated that dose distributions were reproducible in terms of both target coverage and organs at risk (OARs) sparing. [ABSTRACT FROM AUTHOR]

The response of Fricke xylenol orange gelatin dosimeter has been studied to investigate the possibility of achieving a calibration method based on a preirradiation procedure. With this aim, different preirradiation parameters have been tested, and the system response to subsequent irradiations has been investigated. Both Fricke gel layers and cuvettes were considered, and no dependence on shape and wall material was observed. An increase of the system response was observed, depending on the total absorbed dose and not on the number of subsequent irradiations performed, as evidenced by the changes of the absorption spectra shapes. Moreover, different calibration curves, and consequently different sensitivities, were obtained with different preirradiation parameters. In order to propose a calibration procedure, further studies are of fundamental importance to deeper comprehending the influence of preirradiation parameters on the system sensitivity and response. In particular, a systematic analysis of the whole absorption spectra has proved to be central. [ABSTRACT FROM AUTHOR]

Simple Summary: Radiotherapy is the cornerstone of treatment of nasopharyngeal cancer, in different settings with or without chemotherapy. This role has been recently strengthened by the introduction of proton therapy, as a radiation treatment option for head and neck cancer, obtaining improved plans with a reduced dose to organs-at-risk. Definition of strategies to identify patients who would benefit the most from proton therapy in terms of reduced toxicity is highly desirable, due to limited availability and higher costs of this treatment option. Two parallel working pipelines were depicted in this study for nasopharyngeal cancer patients. The introduction of a synthetic index describing the overall expected reduction in toxicities in the head and neck region with proton therapy was supported by the application of the well-established model-based selection methodology, relative to the same patient cohort. Based on this analysis, the fraction of nasopharyngeal cancer patients expected to receive a benefit with proton therapy was in line with the Dutch experience for the head and neck cancer population. (1) Background: we proposed an integrated strategy to support clinical allocation of nasopharyngeal patients between proton and photon radiotherapy. (2) Methods: intensity-modulated proton therapy (IMPT) plans were optimized for 50 consecutive nasopharyngeal carcinoma (NPC) patients treated with volumetric modulated arc therapy (VMAT), and differences in dose and normal tissue complication probability (ΔNTCPx-p) for 16 models were calculated. Patient eligibility for IMPT was assessed using a model-based selection (MBS) strategy following the results for 7/16 models describing the most clinically relevant endpoints, applying a model-specific ΔNTCPx-p threshold (15% to 5% depending on the severity of the complication) and a composite threshold (35%). In addition, a comprehensive toxicity score (CTS) was defined as the weighted sum of all 16 ΔNTCPx-p, where weights follow a clinical rationale. (3) Results: Dose deviations were in favor of IMPT (ΔDmean ≥ 14% for cord, esophagus, brainstem, and glottic larynx). The risk of toxicity significantly decreased for xerostomia (−12.5%), brain necrosis (−2.3%), mucositis (−3.2%), tinnitus (−8.6%), hypothyroidism (−9.3%), and trismus (−5.4%). There were 40% of the patients that resulted as eligible for IMPT, with a greater advantage for T3–T4 staging. Significantly different CTS were observed in patients qualifying for IMPT. (4) Conclusions: The MBS strategy successfully drives the clinical identification of NPC patients, who are most likely to benefit from IMPT. CTS summarizes well the expected global gain. [ABSTRACT FROM AUTHOR]

Background and purpose To study if MO Skin detectors coupled to a trans-rectal ultrasound (TRUS) probe may be used for in vivo dosimetry on the rectal wall surface during US-based HDR prostate brachytherapy and to quantify possible discrepancies between planned and delivered doses. Materials and methods MO Skins are a specific type of MOSFET dosimeter optimized to measure dose in steep dose gradients on interfaces. Two MO Skins were assembled on a TRUS probe used for on-line treatment planning. Measurements of the dose to the rectal wall were performed over 18 treatment sessions and compared to the doses calculated on the pre-treatment plan ( D PRE ) and reconstructed on post-treatment images ( D POST ). Results Averages of the absolute differences between MO Skin readings and D PRE , MO Skin readings and D POST and D PRE and D POST were 6.7 ± 5.1%, 3.6 ± 1.9% and 6.3 ± 4.7%, respectively. Agreement between measurements and D POST was significantly better than between measurements and D PRE (p = 0.002) and D PRE and D POST (p = 0.004). Discrepancy between D POST and D PRE correlated with the time required for treatment planning. Conclusion MO Skin dosimeters integrated to the TRUS probe proved to be an accurate instrument for measuring the dose delivered to the rectal wall in HDR prostate brachytherapy. The delivered doses may differ significantly from those calculated in the treatment plan. [ABSTRACT FROM AUTHOR]

Fiber-optic-coupled scintillation dosimeters are characterized by their small active volume if compared to other existing systems. However, they potentially show a greater stem effect, especially in external beam radiotherapy where the Cerenkov effect is not negligible. In brachytherapy, due to the lower energies and the shorter high dose range of the employed sources, the impact of the stem effect to the detector accuracy might be low. In this work, the stem effect of a Ce 3+ doped SiO 2 scintillation detector coupled to a SiO 2 optical fiber was studied for high dose rate brachytherapy applications. Measurements were performed in a water phantom at changing source-detector mutual positions. The same irradiations were performed with a passive optical fiber, which doesn't have the dosimeter at its end. The relative contribution of the passive fiber with respect to the uncorrected readings of the detector in each one of the investigated source dwell positions was evaluated. Furthermore, the dosimeter was calibrated both neglecting and correcting its response for the passive fiber readings. The obtained absolute dose measurements were then compared to the dose calculations resulting from the treatment planning system. Dosimeter uncertainties with and without taking into account the passive fiber readings were generally below 2.8% and 4.3%, respectively. However, a particular exception results when the source is positioned near to the optical fiber, where the detector underestimates the dose (-8%) or at source-detector longitudinal distances higher than 3 cm. The obtained results show that the proposed dosimeter might be adopted in high dose rate prostate brachytherapy with satisfactory accuracy, without the need for any stem effect correction. However, accuracy further improves by subtraction of the noise signal produced by the passive optical fiber. [ABSTRACT FROM AUTHOR]

Purpose: To report the outcome of a consecutive series of patients with nonmetastatic nasopharyngeal carcinoma (NPC), focusing on the impact of treatment-related factors. Methods and Materials: Between 2000 and 2006, 87 patients with NPC were treated with either conventional (two- or three-dimensional) radiotherapy (RT) or with intensity-modulated RT (IMRT). Of these patients, 81 (93%) received either concomitant CHT (24%) or both induction and concomitant chemotherapy (CHT) (69%). Stage was III in 36% and IV in 39% of patients. Outcomes in this study population were compared with those in the previous series of 171 patients treated during 1990 to 1999. Results: With a median follow-up of 46 months, actuarial rates at 3 years were the following: local control, 96%; local-regional control, 93%; distant control (DC), 90%; disease-free survival (DFS), 82%; overall survival, 90%. In Stage III to IV patients, distant control at 3 years was 56% in patients treated with concomitant CHT only and 92% in patients treated with both induction and concomitant CHT (p = 0.014). At multivariate analysis, histology, N-stage, RT technique, and total RT dose had the strongest independent impact on DFS (p < 0.05). Induction CHT had a borderline effect on DC (p = 0.07). Most dosimetric statistics were improved in the group of patients treated with IMRT compared with conventional 3D technique. All outcome endpoints were substantially better in the study population compared with those in the previous series. Conclusions: Outcome of NPC has further improved in the study period compared with the previous decade, with a significant effect of RT technique optimization. The impact of induction CHT remains to be demonstrated in controlled trials. [Copyright &y& Elsevier]