Radiotherapy in Medulloblastoma—Evolution of Treatment, Current Concepts and Future Perspectives

Abstract

Medulloblastoma is the most frequent malignant brain tumor in children. During the last decades, the therapeutic landscape has changed significantly with craniospinal irradiation as the backbone of treatment. Survival times have increased and treatments were stratified according to clinical and later molecular risk factors. In this review, current evidence regarding the efficacy and toxicity of radiotherapy in medulloblastoma is summarized and discussed mainly based on data of controlled trials. Current concepts and future perspectives based on current risk classification are outlined. With the introduction of CSI, medulloblastoma has become a curable disease. Due to combination with chemotherapy, survival rates have increased significantly, allowing for a reduction in radiation dose and a decrease of toxicity in low- and standard-risk patients. Furthermore, modern radiotherapy techniques are able to avoid side effects in a fragile patient population. However, high-risk patients remain with relevant mortality and many patients still suffer from treatment related toxicity. Treatment needs to be continually refined with regard to more efficacious combinatorial treatment in the future.

Focal versus craniospinal radiation for disseminated atypical teratoid/rhabdoid tumor following favorable response to systemic therapy

“…For disseminated medulloblastoma, the standard radiation field is CSI to 36−39.6 Gy, followed by primary and optional metastatic site (CNS dissemination) boost. 43 However, the developing brain is very sensitive to even low doses of large-volume brain radiation, where the risk of neurocognitive deficits in intelligence quotient, reading, math, and spelling are particularly devastating for very young patients. 44,45 This has resulted in the development and continued evolution of strategies that delay or omit RT for high-risk infant brain tumors, where ATRT outcomes are generally poor, in limited patient numbers, with nonstandardized use of RT.…”

“…Whereas medulloblastomas represent the most common infant brain tumor and as such allows prospective study in greater numbers than ATRT, ATRT represents some of the youngest patients where RT is routinely considered. For disseminated medulloblastoma, the standard radiation field is CSI to 36−39.6 Gy, followed by primary and optional metastatic site (CNS dissemination) boost 43 . However, the developing brain is very sensitive to even low doses of large‐volume brain radiation, where the risk of neurocognitive deficits in intelligence quotient, reading, math, and spelling are particularly devastating for very young patients 44,45 .…”

Helical tomotherapy craniospinal irradiation in primary brain tumours: Toxicities and outcomes in a peadiatric and adult population

“…Planning target volume (PTV) was defined as the CTV with a uniform margin of 0.5 to 1 cm depending on age, in accordance with international guidelines. CSI doses were prescribed as recommended for each tumour type and defined risk groups [16] , [17] , [18] , from 18 to 36 Gy [19] , [20] , [21] .…”

Electron FLASH radiotherapy in vivo studies. A systematic review

“…In view of the curability of this disease, efforts have been made to reduce neurological sequelae without losing the guaranteed effectiveness. For instance, preserving anatomical components, such as the inner ear and the temporal lobes/hippocampus requires a decrease in the boost volume from the posterior fossa to the tumor bed, as explored in the prospective ACNS0331 trial ( 51 ). Lastly, thanks to advancements in oncological therapy, the survival of brain metastatic patients has been prolonged too, making it essential to give even more relevance to tolerance aspects.…”