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OBJECTIVE In this study, different fraction sizes in prostate cancer will be examined using a radiobiological model. METHODS Fifty patients diagnosed with low-risk prostate cancer who were treated between 2009 and 2021 were identified retrospectively. Conventional (CF) and ultra-hypofractionated (HF) volume-adjusted arc plans were calculated for selected prostate patients. Mathematical formulations were created for radiobiological modeling of tumor control probability (TCP) and normal tissue complication probability (NTCP) in the Matlab program. Dose-volume histogram (DVH) data of the plans were examined in the Matlab program. RESULTS Bladder and rectum NTCP values were significantly lower in the HF technique compared to the CF technique (p<0.05). For femoral heads, NTCP was similar (p=0.317). For the planned target volume, TCP values obtained with the HF technique are significantly higher compared to the CF technique (p=0.000). CONCLUSION Higher TCP values were obtained with the HF technique. It has been observed that normal tissues receive lower doses. This may be associated with high local control rates while providing similar toxicity. HF treatment may be preferred in prostate cancer because the total treatment duration is shorter and the dose applied to critical organs is lower. Radiobiological models are very instructive for comparing treatment schemes in radiotherapy plans. The Matlab program we created is a very helpful tool for the radiation oncologist and medical physicist to evaluate their plans. [ABSTRACT FROM AUTHOR]

Objective: To retrospectively determine the long-term outcome of adult intracranial and spinal ependymoma patients treated with postoperative radiation therapy after surgery. Methods: Fourteen adult patients who underwent radiotherapy after suıgeıy at a single center between 1999 and 2022 were included. The endpoints analyzed were overall survival and progression-free survival, together with prognostic factors. Results: The median (range) age was 29.5 (23-58) years. The majority (71.4%) of the tumors were located in the spinal canal and gross total resection was performed in nine (64.3%) patients. Six patients were irradiated after recurrence (spinal n=4, intracranial n=2) of whom three had myxopapillary and two had anaplastic histology. Patients were followed up for a median duration of 106.5 (13-172) months. Overall, 4 patients (intracranial n=3, spinal n=1) had recurrences and died after radiotherapy as a direct result of disease progression during the follow-up period. All of these intracranial tumors exhibited anaplastic histology and the spinal tumor was myxopapillary type. Patients with intracranial lesions had a 5-year survival of 50%> and no patient was alive on the 10th year, compared with 5- and 10-year overall survival of 87.5 % for patients with spinal tumors. Patients with spinal tumors had a 5- and 10-year progression-free survival rate of 52.5%, while those with intracranial lesions had a rate of 25% Conclusion: In low-grade spinal ependymomas radiotherapy appears to control disease, even after recurrence. For myxopapillary ependymoma patients, in subtotally resected intracranial and all high-grade tumors, regardless of the extent of resection, adjuvant radiotherapy should be administered. [ABSTRACT FROM AUTHOR]

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