Cancer places a heavy burden on healthcare systems. The cost of cancer drugs is increasing, driven largely by the introduction of new, ever more innovative cancer treatments. This raises questions about value for money and the future sustainability of cancer care, and presents significant challenges for decision-makers in providing all patients with access to treatments and effective new cancer medicines. The aims of this article are to provide an understanding of how sustainability in cancer care is defined, what signs indicate that the limits of sustainability are being reached, and what potential impact this may have on patients with cancer within Europe. Each country is faced with making difficult decisions about the allocation of healthcare resources to cancer care, to best meet the health needs of their patients. Determining the value of individual cancer drugs can help to inform these decisions, because premium pricing for incremental innovation is no longer sustainable. When the cost of cancer care becomes unsustainable, countries may be forced to restrict health expenditure by limiting demand, cutting spending and reducing investment. This can lead to restricted access to treatment. New, innovative cancer treatments must provide greater value than current options, and measures are needed to contain and reduce expenditure and make best use of scarce resources, without impeding access to effective and safe treatments for all patients.