PurposeTo assess the results and tolerance of radiosurgery/hypofractionated stereotactic radiotherapy performed after craniospinal irradiation for recurrent tumor.MethodsFourteen patients aged 3–46 years, diagnosed with medulloblastoma (10), anaplastic ependymoma (3), and primitive neuroectodermal tumor (1). All patients had craniospinal irradiation (CSI) with the total dose of 30.6–36 Gy and boost to 53.9–60 Gy either during primary or during second-line treatment. Twelve patients were irradiated with a single dose of 6–15 Gy (median 14.5 Gy). One received three fractions of 5 Gy and one six fractions of 5 Gy. In statistical analysis, the Kaplan-Meier method and log-rank test were used. The overall survival was calculated from the date of the end of stereotactic radiosurgery to the date of death or last contact.ResultsRecurrences were diagnosed after the median time of 16 months after the end of primary treatment. Eleven patients died during the follow-up. The follow-up for the 3 patients still alive was 6.7, 40.5, and 41.4 months, respectively. One- and 2-year overall survival (OS) was 70% and 39%. Patients who had ECOG performance status of 0 at the time of diagnosis of the disease trended to have better 2-year OS compared to those evaluated as ECOG 1 (p = 0.057). Treatment results were evaluable in 12 patients. Local control (stabilization or regression of the lesion) was achieved in 9 (75%). Overall disease progression was 67%. No patient developed radiation-induced necrosis. The treatment was well tolerated and no serious adverse effects were observed. Eleven patients were given steroids as a prevention of brain edema and four of them needed continuation of this treatment afterwards. In 7 patients, symptoms of brain edema were observed during the first weeks after reirradiation.ConclusionsStereotactic radiosurgery or hypofractionated stereotactic radiotherapy is an effective treatment method of the local recurrence after CSI and can be performed safely in heavily pre-treated patients.

Treatment plan comparisonGastric cancer Conformal radiotherapy a b s t r a c tAim: The purpose of this study was to compare conformal radiotherapy techniques used in the treatment of gastric cancer patients. The study is dedicated to radiotherapy centres that have not introduced dynamic techniques in clinical practice. Background:The implementation of multi-field technique can minimise the toxicity of treatment and improve dose distribution homogeneity in the target volume with simultaneous protection of organs at risk (OaRs). Treatment plan should be personalised for each patient by taking into account the planning target volume and anatomical conditions of the individual patient. Materials and methods:For each patient, four different three dimensional conformal plans were compared: 2-field plan, 3-field plan, non-coplanar 3-field plan and non-coplanar 4-field plan. Dose distributions in a volume of 107% of the reference dose, and OaRs such as the liver, kidneys, intestines, spinal cord, and heart were analysed. Results BackgroundGastric cancer is the third most frequent cause of death from cancer worldwide, with 723,027 deaths registered in 2012. 1 The primary treatment modality of gastric cancer is surgery. 16 This treatment strategy is frequently employed in the early stage of cancer. Radical operation (R0) can be performed in approximately 50% of patients because of the diagnosis of cancer in the locally advanced or dispersal stage. Since the INT-0116 study was published, the standard for pT 2-4 N 0-3 or pT 1 N 1-3 gastric cancer is postoperative radiochemotherapy. 2,6 At some oncology centres, R1 surgical resection is also an indication for postoperative radiochemotherapy. 3 Implementation of this scheme enhances both local cure and the 5-year survival by approximately 15% compared with independent surgery treatment. Initially, at many radiotherapy departments, a recommended two dimension (2D) technique using two opposing fields was applied for gastric cancer treatment. The constraint of 2D radiotherapy for the abdominal area is the close localisation of organs at risk such as the kidneys, liver, intestines and spinal cord. Consequently, this radiotherapy induced high hematologic toxicity of the digestive system and was completed earlier than planned in 17% of patients. 4 With recent advances in technology, computer dose distribution calculations have been shown to allow the introduction of three dimension (3D) conformal techniques (conformal radiotherapy; CRT) in common applications. These techniques turn out to be more effective in achieving high, homogeneous dose distribution in the target volume with simultaneous sparing of normal tissues. In the 3D conformal technique the shape of the planning target volume (PTV), mutual localisation of the target volume and organs at risk are all considered. 5 Dose distribution in the 3D technique allows the acquisition of more information than that in 2D planning. 3D planning exposes the local maximum of the dose distribution (hot spots) or allows localised region...

The aim of this study is to answer the question whether the calculated dose distributions for HD and Millennium collimators (Varian Medical Systems) are equivalent for large treatment volumes.Background: Modern biomedical linacs are equipped with multileaf collimators where leaves can be of different widths. Thinner leaves allow better fit to desired (tumor) shape. At the same time, however, the maximum size of the field that can be obtained with the collimator is also reduced. Varian Medical Systems HD and Millennium collimators can be a good sample. They have 40 cm or 22 cm × 40 cm maximal field size at the isocenter, respectively. Materials and methods:This paper presents the comparison of selected statistical and dosimetric parameters achieved for treatment plans where the beams for a HD collimator had to be merged because of the size of the tumor volume.Results and discussion: Achieved results show that, independently from irradiated volume, there is no statistically significant difference for calculated dose distributions, integral doses, MU values and coefficients evaluating dose distributions for HD and Millennium collimators.Conclusions: Results show that both types of collimators can be used interchangeably for preparing the treatment plans for large tumor volume without quality reduction of the prepared treatment plan.

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