Tumors induce the formation of novel capillaries (angiogenesis) to access additional nutrients and sustain their progression. Here, we present our effort to simulate tumor-induced vascularization in a patient-specific way, combining Optical Coherence Tomography (OCT) images of three different patients with a Phase-Field Model (PFM) featuring tumor growth and angiogenesis [1]. Our case study is Retinal Hemangioblastoma (RH), a retinal tumor invariantly associated with dense vascular networks. The reason for this characteristic is genetic. RH is the most frequent manifestation of the von Hippel-Lindau disease (VHL), a cancer-predisposition syndrome caused by the mutation of the VHL protein (pVHL). pVHL mutation leads to the overexpression of several angiogenic factors, which explain the highly vascular nature of RH [2]. RH is a fascinating case study for tumor-induced angiogenesis for several reasons. Its small dimension allows us to simulate the full tumor volume and its vascular network in 3D with a reasonable computational effort. The mutation of pVHL decouples vascularization and hypoxia, reducing the model complexity. Moreover, the RH shape and vascular network can be observed with unprecedented detail since the introduction of OCT and OCT Angiography (OCTA) [3]. Our model can recapitulate tumor development as observed in the medical images, in agreement with the mainstream theory for the pathology of this tumor. Moreover, our simulations show that it is likely that RHs must reach a critical mass before inducing angiogenesis, after which complete tumor vascularization can occur in the order of days. This observation provides a new explanation for the disappointing results of anti-angiogenic therapy on this tumor, which resulted ineffective so far. If angiogenesis occurs so rapidly, even the time of diagnosis might be too late to start the treatment. References: [1] R. D. M. Travasso, E. C. Poiré, M. Castro, J. C. Rodrguez-Manzaneque, A. Hernández-Machado, PLoS One. 6, e19989 (2011). [2] S. Karimi, A. Arabi, T. Shahraki, S. Safi, J. Ophthalmic Vis. Res. 15, 78 (2020). [3] P. Sagar, R. Rajesh, M. Shanmugam, V. K. Konana, D. Mishra, Indian J. Ophthalmol. 66, 872–876 (2018).