Dosimetric Evaluation of 3D-CRT and IMRT Treatment Techniques in Medulloblastoma

International Journal of Biomedicine 15(4) (2025) 685-689 http://dx.doi.org/10.21103/Article15(4)_OA6 ORIGINAL ARTICLE INTERNATIONAL JOURNAL OF BIOMEDICINE Radiology Dosimetric Evaluation of 3D-CRT and IMRT Treatment Techniques in Medulloblastoma Blerim Rrakaqi1,3, Ervis Telhaj2, Besim Xhafa1, Ylli Kaçiu3*, Armend Jashari1,3*, Ramiz Ukaj1,3 Alma Mater Europae Campus College “REZONANCA,” Prishtina, Kosovo Western Balkans University, Tirana, Albania 3 University Clinical Center of Kosovo, Prishtina, Kosovo 1 2 Abstract A primitive neuroectodermal tumor (PNET) of the cerebellum, called medulloblastoma, is an aggressive, fast-growing brain tumor. This study aims to compare the dosimetric distribution of two radiotherapy techniques—three-dimensional conformal radiation therapy (3D-CRT) and intensity-mod ulated radiation therapy (IMRT)—in patients with medulloblastoma by evaluating planning target volume (PTV) and exposure of organs at risk (OARs). In a 15-year retrospective analysis, considerable number of patients (aged 3–30 years) initially treated with 3D-CRT and subsequently with IMRT (volumetric modulated arc therapy is now used but not included in this comparison) were evaluated. Treatment plans were created in the planning system using the Monte Carlo Convolution/Superposition algorithm. Dose distributions were assessed via dose–volume histograms, and the maximum doses received by the hippocampus, brainstem, and spinal cord were compared between the two techniques. Both 3D-CRT and IMRT achieved complete coverage of the PTV. IMRT demonstrated a significant reduction in dose to critical structures, thereby lowering the risk of neurocognitive and endocrine side effects, whereas 3D-CRT delivered higher radiation levels to surrounding normal tissues. Average treatment times for IMRT were approximately 20–30% longer than for 3D-CRT. IMRT provides a more conformal dose distribution, with enhanced protection of OAR, potentially permitting higher tumor doses and improved long-term outcomes in pediatric patients. However, the choice between 3D-CRT and IMRT should be made on a case-by-case basis, taking into account the contour delineation, technical availability, and the patient’s tolerance for treatment duration. (International Journal of Biomedicine. 2025;15(4):685-689.) Keywords: medulloblastoma • 3D-CRT • IMRT For citation: Rrakaqi B, Telhaj E, Xhafa B, Kaçiu Y, Jashari A. Ukaj R. Dosimetric Evaluation of 3D-CRT and IMRT Treatment Techniques in Medulloblastoma. International Journal of Biomedicine. 2025;15(4):685-689. doi:10.21103/Article15(4)_OA6 Abbreviations 3D-CRT, three-dimensional conformal radiation therapy; CSI, craniospinal irradiation; CT, computer tomography; CTV, clinical target volume; GTV, gross tumor volume; IMRT, intensity-modulated radiation therapy; MRI, magnetic resonance imaging; OAR, organ at risk; PTV, planning target volume; VMAT, volumetric modulated arc therapy. Introduction Medulloblastoma is the most common malignant brain tumor in children, accounting for approximately 20% of all pediatric brain tumors. Any patient presenting with neurological symptoms should undergo a complete evaluation, including a neurological examination. If a brain tumor is suspected, the patient is typically referred for brain imaging. Neuroimaging plays a key role in the diagnosis and assessment of medulloblastoma dissemination. Magnetic resonance imaging (MRI) and computed tomography (CT) 686 B. Rrakaqi et al. / International Journal of Biomedicine 15(4) (2025) 685-689 provide detailed images of the brain and spinal cord, enabling the detection of tumors and their anatomical relationships to surrounding structures.1,2 In pediatric patients, contrast administration improves lesion visualization, and sedation may be required to obtain high-quality images. In rare cases, a medulloblastoma or another primitive neuroectodermal tumor (PNET) can be detected by prenatal ultrasound.3 Some early studies suggested that the diagnosis could be established solely based on imaging without the need for a biopsy.1,2,3 However, according to the WHO Classification of CNS Tumours 2021 and SIOP-Europe 2023 guidelines, final diagnosis requires histopathological verification and molecular characterization, which are essential for accurate risk stratification and optimal treatment planning. The modern classification system divides medulloblastomas into four main molecular groups: WNTactivated – very favorable prognosis; often eligible for reduced CSI dose, HH-activated, TP53-wildtype – intermediate prognosis, SHH-activated, TP53-mutant – poor prognosis; often treatment-resistant, Non-WNT/Non-SHH – includes Group 3 and Group 4, with diverse molecular profiles and prognoses.4,5 This molecular classification, combined with histological and clinical features, has enabled a more personalized approach to treatment. Radiotherapy, combined with surgery and chemotherapy, is a cornerstone in the management of medulloblastoma. For standard-risk patients, this multimodal approach achieves 5-year survival rates of 75–85%.1 Age is a key factor in risk stratification: patients under 3 years of age are treated with specific protocols to avoid or reduce craniospinal irradiation due to the high risk of long-term side effects. One of the most common and detrimental late effects of treatment is neurocognitive decline, which is directly related to the radiation dose delivered to the brain.6,7 The hippocampus and temporal lobes are critical structures for memory formation and cognitive function. Studies in both animal models and patients have demonstrated that radiation-induced disruption of hippocampal neurogenesis leads to significant cognitive deficits. For this reason, modern radiotherapy techniques such as intensity-modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), and proton therapy are increasingly used to limit the dose to critical structures while maintaining tumor control. Hippocampal-sparing craniospinal irradiation (CSI) is an emerging strategy designed to reduce the risk of long-term cognitive impairment. In standard treatment, craniospinal irradiation (CSI) is delivered at a dose of 23.4–36 Gy, followed by a boost to the posterior fossa up to 54–55.8 Gy.1,7 Typical margins for the gross tumor volume (GTV) and clinical target volume (CTV) range from 0.5cm to 1.5 cm, with an additional 0.5 cm added to generate the planning target volume (PTV). In WNT-activated and standard-risk patients, protocols with reduced CSI doses are being investigated to minimize toxicity without compromising survival. Methodology Over 15 years at our center, a considerable number of patients diagnosed with primitive neuroectodermal tumors (PNET), including medulloblastoma, were treated. The patients’ ages ranged from 3 to 30 years, encompassing both pediatric and young adult populations. Initially, treatments were delivered using the three-dimensional conformal radiation therapy (3D-CRT (...truncated)