To evaluate between Heterogeneity Index (HI) and Gradient Index (GI) correlation for high dose Stereotactic radiotherapy (SRT) / Stereotactic radiosurgery (SRS) using Versa HD^® lineer accelerator. Nine patients with single metastasis were used in this study. Patient’s treatment planning were performed using Monaco5.1^® Treatment planning system (TPS) with non-coplanar 6MV Flattening filter free (FFF) beams by partial Volumetric modulated arc therapy (VMAT) tecnique for each patient. We determined three different size of metastasis catagory which are less than 1cc, between 1cc and 5cc and larger than 5cc volume. Also, three different HI were calculated for each patients. These are 1.10, 1.20 and 1.30. Mean GI was determined 8.57±2.2 for 1.10 HI, 7.23±1.7 for 1.20 HI and 6.0±1.1 for 1.30 HI for less than 1cc metastasis. Then GI was determined 4.77±0.4 for 1.10 HI, 4.37±0.3 for 1.20 HI and 3.97±0.3 for 1.30 HI for between 1cc and 5cc metastasis. Finally, GI was determined 4.00±0.5 for 1.10 HI,3.63±0.5 for 1.20 HI and 3.27±0.4 for 1.30 HI for larger than 5cc metastasis. These results show that GI depends on significantly size and HI of metastasis especially for less than 1cc.

Objective: In the current classification of brain tumors of the World Health Organization, various tumor histologies have been categorized under the main heading of glial tumors. The subgroup of low-grade gliomas comprises grade 2 diffuse astrocytic and oligodendroglial tumors. Methods: The primary treatment of low-grade gliomas is surgery. Safe maximal resection is the widest possible resection without causing additional neurological damage. It increases survival and reduces existing neurological symptoms. Maximal safe resection may not be achieved because of tumor infiltration or proximity to sensitive motor/sensory function areas. Although radio diagnostic and surgical technique advancements have improved, residual tumors are detected in the majority of patients. Results: Adjuvant treatment of residual low-grade gliomas is controversial. The European Organisation for Research and Treatment of Cancer (EORTC) study showed that early radiotherapy after surgery extended progression-free survival for 2 years without an overall survival benefit. After this study, it has been adopted in clinical practice that high-risk patients receive early radiotherapy and low-risk groups receive radiotherapy after progression. Certain risk factors have been determined from Radiation Therapy Oncology Group (RTOG) and EORTC studies. The high-risk factors are age over 40 years, partial resection, tumor size over 5 cm, not having isocitrate dehydrogenase mutation, and tumor progression or recurrence. Adjuvant radiotherapy and concurrent chemotherapy are recommended achieving improved progression-free survival and overall survival in patients with high-risk factors. In the low-risk group, radiotherapy may be delayed until progression. Conclusions: Low-grade gliomas are slow progressing tumors. To detect progression in follow-up, it is recommended to compare follow-up magnetic resonance images with the initial reference magnetic resonance images, not with the previous control. Cite this article as: Dağdelen M, Demir E, Uzel ÖE. Radiotherapy in the treatment of low-grade gliomas. Cerrahpaşa Med J. February 12, 2022. 46(1):1-5.

To evaluate dose distribution of Volumetric modulated arc therapy (VMAT) planning tecnique using Versa HD^® lineer accelerator to deliver Total Body Irradiation (TBI) on the coach. Eight TBI patient’s Treatment Planning System (TPS) were performed with dual arc VMAT for each patient. The VMAT-TBI consisted of three isocentres and three dual overlapping arcs. The prescribed dose was 12 Gy. Mean dose to lung and kidney were restricted less than 10 Gy and max. dose to lens were restricted less than 6 Gy. The plans were verified using 2D array and ion chamber. The comparison between calculation and measurement were made by γ-index analysis and absolute dose. An average total delivery time was determined 923±34 seconds and an average MU was determined 2614±228 MUs for dual arc VMAT. Mean dose to lungs was 9.7±0.2 Gy, mean dose to kidneys was 8.8±0.3 Gy, max. dose to lens was 5.5±0.3 Gy and max. dose was 14.6±0.3 Gy, HI of PTV was 1.13±0.2, mean dose to PTV was 12.6±1.5 Gy and mean γ-index pass rate was %97.1±1.9. The results show that the tecnique for TBI using VMAT on the treatment coach is feasible.