The incidence of cancer is on the rise globally. Under particular circumstances, patients are willing to travel abroad for healthcare treatments. We know relatively little however about patients travelling overseas for cancer-related screening, diagnosis and treatment. Where do patients go, for what treatments, what are their motivations, decision-making processes and treatment experiences? What do we know about patient safety and risk, and outcomes? More broadly, what are the ethical and legal implications? This review presents the first published assessment of what we term 'transnational oncology treatment' , defined as patients travelling overseas or across borders for cancer screening, diagnosisand treatment. The review undertakes detailed search and retrieval of the literature, using an accepted scoping review method. We present a narrative review of existing knowledge and themes, identifying coverage and gaps. There is a five-fold agenda for future investigation: trajectories and itineraries; in depth focus on treatment decisions, experiences and outcomes; locating patient travel within wider health system analysis; exploration of professional perspectives and coordination; and situating travel within the context of health trade. Such an agenda is multidisciplinary and wide-ranging, encompassing epidemiology, health econom-