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AIM: Evaluating the recurrence patterns of high-grade astrocytomas in patients who were treated with radiotherapy (RT) plus temozolomide (TMZ). BACKGROUND: The current literature suggests that reducing the margins added to the CTV does not significantly change the risk of recurrence and overall survival; thus, we decided to analyze our data and to examine the possibility of changing the adopted margins. MATERIALS AND METHODS: From February 2008 till September 2013, 55 patients were treated for high-grade astrocytomas, 20 patients who had been confirmed to have recurrence were selected for the present study. Post-operative MRI was superimposed on the planning CT images in order to correlate the anatomical structures with the treatment targets. Recurrences were defined according to the Response Assessment Criteria for Glioblastoma. The mean margins of the PTVinitial and PTVboost were 1.2 cm and 1.4 cm, respectively. The analysis of the percentage of the recurrence volume (Volrec) within the 100% isodose surface was based on the following criteria: (I) Central: >95% of the Volrec; (II) In-field: 81-95% of the Volrec; (III) Marginal: 20-80% of the Volrec; and (IV) Outside: <20% of the Volrec. RESULTS: Of the 20 patients, 13 presented with central recurrences, 3 with in-field recurrences, 2 with marginal recurrences and 2 with outside recurrences. Therefore, the lower Volrec within 100% of the prescribed dose was considered in the classification. CONCLUSIONS: Of the selected patients, 80% had ≥81-95% of the Volrec within 100% of the prescribed dose and predominantly had central or in-field recurrences. These results are comparable with those from the literature.
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Abstract Objective: To evaluate three-dimensional translational setup errors and residual errors in image-guided radiosurgery, comparing frameless and frame-based techniques, using an anthropomorphic phantom. Materials and Methods: We initially used specific phantoms for the calibration and quality control of the image-guided system. For the hidden target test, we used an Alderson Radiation Therapy (ART)-210 anthropomorphic head phantom, into which we inserted four 5mm metal balls to simulate target treatment volumes. Computed tomography images were the taken with the head phantom properly positioned for frameless and frame-based radiosurgery. Results: For the frameless technique, the mean error magnitude was 0.22 ± 0.04 mm for setup errors and 0.14 ± 0.02 mm for residual errors, the combined uncertainty being 0.28 mm and 0.16 mm, respectively. For the frame-based technique, the mean error magnitude was 0.73 ± 0.14 mm for setup errors and 0.31 ± 0.04 mm for residual errors, the combined uncertainty being 1.15 mm and 0.63 mm, respectively. Conclusion: The mean values, standard deviations, and combined uncertainties showed no evidence of a significant differences between the two techniques when the head phantom ART-210 was used.
Resumo Objetivo: Comparar os erros de posicionamento e erros residuais translacionais tridimensionais de uma radiocirurgia guiada por imagem, frame versus frameless, com uso de um objeto simulador antropomórfico. Materiais e Métodos: Para a calibração e qualidade do sistema de imagem foram utilizados objetos simuladores específicos. Para o teste hidden target foi utilizado o crânio do objeto simulador antropomórfico Alderson Radiation Therapy (ART)-210, dentro do qual foram inseridas quatro esferas metálicas de 5 mm de diâmetro como volumes alvos de tratamento. Imagens tomográficas foram realizadas com o ART-210 devidamente posicionado para ambos os métodos de imobilização. Resultados: Para o método frameless, a média foi 0,22 ± 0,04 mm para os erros setup e 0,14 ± 0,02 mm para os erros residuais, apresentando uma incerteza combinada de 0,28 mm e 0,16 mm, respectivamente. Para o método frame, a média foi 0,73 ± 0,14 mm para os erros setup e 0,31 ± 0,04 mm para os erros residuais, apresentando uma incerteza combinada de 1,15 mm e 0,63 mm, respectivamente. Conclusão: Com base nas médias, desvios-padrão e incertezas combinadas, os resultados mostraram não haver evidências de diferença significativa entre as técnicas em questão quando utilizado um objeto simulador antropomórfico craniano ART-210.