Planning strategies in volumetric modulated are therapy for breast.

PURPOSE: In breast radiotherapy with intensity modulation, it is a well established practice to extend the dose fluence outside the limit of the body contour to account for small changes in size and position of the target and the rest of the tissues due to respiration or to possible oedema. A simple approach is not applicable with RapidArc volumetric modulated are therapy not being based on a fixed field fluence delivery. In this study, a viable technical strategy to account for this need is presented. METHODS: RapidArc (RA) plans for six breast cancer patients (three right and three left cases), were optimized (PRO version III) on the original CT data set (0) and on an alternative CT (E) generated with an artificial expansion (and assignment of soft-tissue equivalent HU) of 10 mm of the body in the breast region and of the PTV contours toward the external direction. Final dose calculations for the two set of plans were performed on the same original CT data set O, normalizing the dose prescription (50 Gy) to the target mean. In this way, two treatment plans on the same CT set O for each patient were obtained: the no action plan (OO) and the alternative plan based on an expanded optimization (EO). Fixing MU, these two plans were then recomputed on the expanded CT data set and on an intermediate one (with expansion = 5 mm), to mimic, possible changes in size due to edema during treatment or residual displacements due to breathing not properly controlled. Aim of the study was to quantify the robustness of this planning strategy on dose distributions when either the OO or the EO strategies were adopted. For all the combinations, a DVH analysis of all involved structures is reported. RESULTS: I. The two optimization approaches gave comparable dose distributions on the original CT data set. II. When plans were evaluated on the expanded CTs (mimicking the presence of edema), the EO approach showed improved target coverage if compared to OO: on CT_10 mm, Dv = 98% [%]= 92.5 +/- 0.9 and 68.5 +/- 3.1, respectively, for EO and OO. Minor changes were registered in organs at risk sparing for both EO and OO. III. From dose distributions and DVHs, EO approach allowed to irradiate at near to prescription levels also the expanded fraction of the target: this would account also for residual intrafraction movements. CONCLUSIONS: The proposed plan strategy could represent a robust approach to account for moderate changes in target or body volume during the course of breast radiotherapy and to account for residual intrafractional respiratory motion in volumetric modulated are therapy. The strategy, logistically simple to implement requiring only modifications to the standard planning workflow was routinely implemented at author's institute for treatment of breast patients with RapidArc.

Minimally Invasive Stereotactical Radio-ablation of Adrenal Metastases as an Alternative to Surgery / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: The purpose of this study was to study the clinical outcome for patients with metastases of the adrenal gland treated with stereotactic body radiation therapy. MATERIALS AND METHODS: Forty-six patients were studied retrospectively. The dose prescription was 40 Gy in four fractions. Dosimetric analysis was performed using the dose volume histograms while clinical outcome was assessed using actuarial analysis with determination of the overall survival (OS) and local control (LC) rates. RESULTS: The planning objectives were met for all patients. With a median follow-up period of 7.6 months, at the last follow-up 42 patients (91.3%) were alive and four had died because of distant progression. The actuarial mean OS was 28.5±1.6 months, the median was not reached. One-year and 2-year OS were 87.6±6.1%. None of the risk factors was significant in univariate analysis. Actuarial mean LC was 14.6±1.8 months (95% confidence interval [CI], 11.0 to 18.2) and median LC was 14.5±2.0 months (95% CI, 10.5 to 18.5). One-year and 2-year LC were 65.5±11.9% and 40.7±15.8%, respectively. A mild profile of toxicity was observed in the cohort of patients. Forty patients (86.9%) showed no complication (grade 0); two patients reported asthenia, six patients (13.1%) reported either pain, nausea, or vomiting. Of these six patients, five patients (10.9%) were scored as grade 1 toxicity while one patient (2.2%) was scored as grade 2. CONCLUSION: Stereotactic body radiation therapy treatment provided an adequate clinical response in the management of adrenal gland metastases.

Hypofractionated Stereotactic Radiation Therapy in Recurrent High-Grade Glioma: A New Challenge / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: The aim of this study was to evaluate outcomes of hypofractionated stereotactic radiation therapy (HSRT) in patients re-treated for recurrent high-grade glioma. MATERIALS AND METHODS: From January 2006 to September 2013, 25 patients were treated. Six patients underwent radiation therapy alone, while 19 underwent combined treatment with surgery and/or chemotherapy. Only patients with Karnofsky Performance Status (KPS) > 70 and time from previous radiotherapy greater than 6 months were re-irradiated. The mean recurrent tumor volume was 35 cm3 (range, 2.46 to 116.7 cm3), and most of the patients (84%) were treated with a total dose of 25 Gy in five fractions (range, 20 to 50 Gy in 5-10 fractions). RESULTS: The median follow-up was 18 months (range, 4 to 36 months). The progression-free survival (PFS) at 1 and 2 years was 72% and 34% and the overall survival (OS) 76% and 50%, respectively. No severe toxicity was recorded. In univariate and multivariate analysis extent of resection at diagnosis significantly influenced PFS and OS (p 50 cm3), respectively (p=0.26). CONCLUSION: In our experience, HSRT could be a safe and feasible therapeutic option for recurrent high grade glioma even in patients with larger tumors. We believe that a multidisciplinary evaluation is mandatory to assure the best treatment for selected patients. Local treatment should also be considered as part of an integrated approach.

What is an acceptably smoothed fluence? Dosimetric and delivery considerations for dynamic sliding window IMRT.

BACKGROUND: The study summarised in this report aimed to investigate the interplay between fluence complexity, dose calculation algorithms, dose calculation spatial resolution and delivery characteristics (monitor units, effective field width and dose delivery against dose prediction agreement) was investigated. A sample set of complex planning cases was selected and tested using a commercial treatment planning system capable of inverse optimisation and equipped with tools to tune fluence smoothness. METHODS: A set of increasingly smoothed fluence patterns was correlated to a generalised expression of the Modulation Index (MI) concept, in nature independent from the specific planning system used that could therefore be recommended as a predictor to score fluence "quality" at a very early stage of the IMRT QA process. Fluence complexity was also correlated to delivery accuracy and characteristics in terms of number of MU, dynamic window width and agreement between calculation and measurement (expressed as percentage of field area with a gamma > 1 (%FA)) when comparing calculated vs. delivered modulated dose maps. Different resolutions of the calculation grid and different photon dose algorithms (pencil beam and anisotropic analytical algorithm) were used for the investigations. RESULTS AND CONCLUSION: i) MI can be used as a reliable parameter to test different approaches/algorithms to smooth fluences implemented in a TPS, and to identify the preferable default values for the smoothing parameters if appropriate tools are implemented; ii) a MI threshold set at MI < 19 could ensure that the planned beams are safely and accurately delivered within stringent quality criteria; iii) a reduction in fluence complexity is strictly correlated to a corresponding reduction in MUs, as well as to a decrease of the average sliding window width (for dynamic IMRT delivery); iv) a smoother fluence results in a reduction of dose in the healthy tissue with a potentially relevant clinical benefit; v) increasing the smoothing parameter s, MI decreases with %FA: fluence complexity has a significant impact on the accuracy of delivery and the agreement between calculation and measurements improves with the advanced algorithms.