Fluid flow in tissue plays an important role in the delivery of oxygen, nutrients and therapeutic agents. The physiology of tumour tissues exhibits several distinct features that influence fluid flow which can potentially promote tumour invasiveness and limit drug delivery. As tumours grow beyond the limit at which preexisting vasculature is able to sufficiently deliver blood, hypoxia develops which can trigger angiogenesis (Carmeliet and Jain
2000; Liao and Johnson
2007). This leads to the formation of aberrant vascular networks with non-uniformly distributed blood vessels that lack hierarchy and differentiation. Excessive branching can be found with loops, blind ends, arteriovenous shunts and erratic changes in diameter which can result in impaired blood perfusion (Less
et al.
1991). Cellular abnormalities of blood vessels lead to poor vessel stability and large inter-endothelial gaps that allow for excessive leakage of plasma (Baluk
et al.
2005). In the tumour extravascular space, the extracellular matrix (ECM) is produced at a high rate, generating mechanical stress which combined with the leaky vessels leads to high interstitial fluid pressure (IFP) (Heldin
et al.
2004). These properties act together to cause abnormal fluid flow in tumours which can be heterogenous and vary from patient to patient (Swartz and Lund
2012). Most therapeutics are injected intravenously and need to reach the tumour site, distribute within the vascular network, permeate through the vessel wall and travel across the interstitial space to reach cancer cells (Zhan
et al.
2018). Hence, abnormal blood flow, reduced extravasation and pressure gradients caused by high IFP can result in poor accumulation and distribution of therapeutic macromolecules. Additionally, high IFP and poor perfusion have been associated with increased metastatic potential and poor prognosis (Hompland
et al.
2014; Munson and Shieh
2014). Therefore, gaining deep insight into fluid dynamics in tumour tissue is necessary as it plays a key role in tumour growth, metastasis and the delivery of therapeutics (Dewhirst and Secomb
2017).