Treating the invisible target: treatment planning targeting the microscopic tumor spread in gliomas.

Introduction: Glioblastoma (GBM) is the most common primary malignant brain tumor in adults, but treatment outcome is poor, and tumor recurrence is often unavoidable. Evidence suggests that regions with tumor cell densities below the medical imaging visibility threshold are more prevalent than the current treatment methodologies account for. This study aimed to explore different treatment planning strategies that account for the microscopic tumor cell distribution. Methods: A diffusion-proliferation model was used to predict the tumor spread in three patients with GBMs, each presenting different degrees of complexity. The tumor spread was quantified as the invasion volume Results: All dose plans generated using the first methodology were clinically acceptable in terms of tumor coverage and sparing of organs at risk. The mean quality index Discussion: Incorporating tumor spread models into treatment planning for GBM is feasible and warrants further investigation to potentially enhance treatment outcomes. Dose mimicking approaches based on reference dose distribution require careful planning and become particularly challenging for large, complex targets.