Amino-acid PET based radiation treatment in an animal model for glioblastoma.

Glioblastoma is the most aggressive and most common primary brain tumour in adults. Even with the current state-of- the-art treatment of postoperative combined radiation therapy (RT) and chemotherapy, the median survival is only 12-14 months. Therefore, there is an urgent need for alternative treatment strategies in glioblastoma patients. In our research group, we investigate the added-value of dose painting strategies. More specifically the focus is on incorporating molecular imaging information in the RT plan for glioblastoma with the aim of delivering a non-uniform dose to the so called biological tumour volume. Tumour volume delineation for RT planning in glioblastoma is currently based on anatomical imaging techniques, such as computed tomography (CT) and conventional magnetic resonance imaging (MRI). Importantly, these structural imaging techniques cannot identify the most aggressive and/or radiation resistant parts within the tumour, which are probably responsible for treatment failure and tumour recurrence. Moreover, currently the tumour volume is being irradiated with a homogeneous dose. This is because it is assumed that the tumour consists of tumour cells that share similar behavioural characteristics and are therefore equally malignant and/or radiation resistant or sensitive. This assumption is obviously not correct. Based on molecular imaging techniques, such as positron emission tomography (PET), it is clear that the tumour volume must be considered as heterogeneous regarding its biological features. Using PET-guided dose painting strategies, a non-uniform dose can be delivered to the tumour based on specific biological features. The rationale is that a non-uniform dose distribution with a higher dose to the most active and/or radiation resistant tumour regions, while keeping the total tumour dose constant, could improve local tumour control without adding toxicity to the adjacent brain.