Dosimetric comparison of different treatment planning techniques with International Commission on Radiation Units and Measurements Report-83 recommendations in adjuvant pelvic radiotherapy of gynecological malignancies.

AIM: The study evaluates the different treatment planning techniques according to three recommendation levels of the International Commission on Radiation Units and Measurements Report-83 in gynecologic cancer patients treated with adjuvant pelvic radiotherapy (APR). MATERIALS AND METHODS: Computerized tomography images of ten endometrial and cervical cancer patients who were treated with APR were assessed. For each patient, five different treatment plans were created. One homogeneity index and four different conformity indexes (CIs) were calculated for three-dimensional conformal radiotherapy (3D-CRT), field-in-field (FIF), seven-field intensity modulated radiotherapy (7-IMRT) with two different degrees beginning (7A-IMRT, 7B-IMRT) and 9-IMRT treatment plans. Dose volume histogram parameters and normal tissue complication probability (NTCP) were compared for organs at risk (OAR). RESULTS: The CI values of the IMRT were closer to 1 with respect to other plans (P < 0.05). The rectum and the bladder volumes which received more than 40 Gy were decreased with IMRT compared to 3D-CRT (P < 0.05). Doses received by the 195 cc volume of the small intestine and NTCP values were significantly decreased with IMRT (P < 0.05). CONCLUSION: IMRT provided more protection than FIF plans at high dose volumes of the OAR; however, it did not show any superiority at low-dose volumes. The NTCP results supported IMRT for only small intestine protection. Because IMRT is increasingly used clinically, the comparison of NTCP will become more common in the near future. Therefore, new prospective studies with sufficient number of patients and appropriate NTCP models are needed for this treatment modality.

Clinical prognostic factors of adjuvant radiation therapy for low-grade gliomas: results of 10 years survival.

OBJECTIVE: Low-grade gliomas compose 5-20% of all glial tumors. The prognosis of the disease can be anticipated by specific clinical factors determined during diagnosis. For this purpose, our study investigated the clinical prognostic factors for low-grade gliomas. METHODS: Patients diagnosed with histopathologically confirmed low-grade glioma, followed by Akdeniz University and Süleyman Demirel University School of Medicine, Department of Radiation Oncology between 1999 and 2013 were included in the study. The examination of survival by single variable analyses were performed by log rank test. For the multivariate analysis, independent factors for the prediction of survival by using possible factors determined by previous analyses were examined by using Cox regression analysis. RESULTS: Fifty-five patients were included in the study. The mean follow-up period was determined as 60 ± 57 (4.5-168.1) months. Five-year overall survival was determined as 69% and 10-year overall survival was determined as 40%. When the potential prognostic factors were studied in Cox regression model, pre-radiotherapy age below 40 and gross-total excision were determined as good prognostic factors. CONCLUSION: We demonstrated that the aggressive surgical resection provided a better survival advantage both in single variable analyses and multivariate analyses. Consequently, although the low number of patients was the most important limitation in our study, we consider that patient age and extent of resection are the most important clinical prognostic factors in low-grade gliomas.

Monte Carlo simulation of stereotactic microbeam radiation therapy: evaluation of the usage of a linear accelerator as the x-ray source.

The usage of linear accelerator-generated x-rays for the stereotactic microbeam radiation therapy technique was evaluated in this study. Dose distributions were calculated with the Monte Carlo code MCNPX. Unidirectional single beams and beam arrays were simulated in a cylindrical water phantom to observe the effects of x-ray energies and irradiation geometry on dose distributions. Beam arrays were formed with square pencil beams. Two orthogonally interlaced beam arrays were simulated in a detailed head phantom and dose distributions were compared with ones which had been calculated for a bidirectional interlaced microbeam therapy (BIMRT) technique that uses synchrotron-generated x-rays. A parallel pattern of the beams was preserved through the phantom; however an unsegmented dose region could not be formed at the target. Five orthogonally interlaced beam array pairs (ten beam arrays) were simulated in a mathematical head phantom and the unsegmented dose region was formed. However, the dose fall-off distance is longer than the one that had been calculated for the BIMRT technique. Besides, the peak-to-dose ratios between the phantom's outer surface and the target region are lower. Therefore, the advantages of the MRT technique may not be preserved with the usage of a linac as the x-ray source.