INDIGO

Brain/CNS tumors
Gliomas (grade I-III)
Adjuvant Therapy
Radiation therapy can be considered the standard treatment option for patients with low-grade gliomas. Typically, a dose of 45–54 Gy is administered in conventional fractionation of 1.8–2 Gy. Patient age, tumor size and location, as well as neurological status, can influence the choice of appropriate radiation therapy. Photon irradiation remains the most commonly used modality. Since the prognosis is generally favorable, preventing late effects is of particular importance. Proton therapy (PRT), with its advantageous physical properties, has the potential to further reduce the burden of treatment-related side effects. However, approximately 20% of all patients exhibit late contrast-enhancing brain lesions (CEBLs) on MRI images 6 to 24 months after treatment. At the HIT in Heidelberg and OncoRay in Dresden, it has been observed that CEBLs occur in very different locations in the brain and in the treatment field. A retrospective analysis has identified potential key factors leading to the occurrence of CEBLs. However, preventing CEBLs with conventional treatment planning strategies is hardly possible. Model-aided risk avoidance denotes the use of model-based CEBL risk calculations as an auxiliary tool for clinical treatment planning: Model-based risk calculations and risk reduction via software-based optimization help the clinician to minimize risk of CEBL occurrence during treatment planning. In this randomized-controlled trial, patients with low-grade glioma will be treated based on treatment plans that rely on either conventional planning strategies (control arm), or planning with model-aided risk avoidance (interventional arm). Through regular follow-up examinations during a period of at least 24 months post treatment, occurrence of CEBLs will be examined by MR imaging in all patients. The hypothesis will be tested that model-aided risk avoidance reduces the overall incidence of CEBLs.
A diagnosis of low-grade glioma (a brain tumor typically associated with a good prognosis) was made. Surgical removal of the tumor is the treatment of choice. Depending on its location, complete removal is not always possible. In such situations, and sometimes even after complete removal depending on other factors, radiation therapy has proven to be a good treatment option. Local radiation therapy has traditionally been performed using a conventional radiation technique using photon radiation (X-rays). However, recent progress has been made using a more modern, more precise radiation technique, proton radiation. With proton radiation, the radiation dose absorbed by the surrounding healthy brain tissue can be significantly reduced, which, depending on the size and location of the area to be irradiated, has a positive effect on potential long-term effects. As part of the study, all patients will receive proton radiation therapy – either conventionally planned or with the help of a novel model-based optimization approach aimed at avoiding the aforementioned treatment-related contrast enhancement. A special radiation planning program is used for this purpose. This program first calculates the risk of subsequent contrast enhancement using a model and then adapts the radiation plan to reduce the likelihood of this enhancement occurring. The aim of this study is to examine the effectiveness, safety, and feasibility of this model-based optimized radiation planning approach. Randomization will be used within the study, meaning that allocation to treatment arms is random and cannot be influenced. The probability of being assigned to either arm is 50% in each case.