The missing components today and the new treatments tomorrow

The history of drug delivery technology is only 60 years old, but various mechanisms of controlled drug delivery have been well established. While numerous controlled release formulations have been developed, only a handful of these approaches has been used successfully as anticancer treatments. Current approaches to deliver anticancer agents to tumors commonly involve the intravenous administration of submicron size formulations. These nanoparticle-based approaches frequently show impressive efficacy in small animal tumor models, but their translation to safe and efficacious clinical outcomes has been disappointing. It is our thesis that the poor success rate of these approaches is primarily due to an insufficient understanding of cancer biology and physiology; knowledge that is necessary to achieve selective and efficient targeting of these anticancer therapies. To substantially improve targeted drug delivery to treat cancers we must know more about how cancer cell heterogeneity, cancer cell drug resistance, as well as tumor properties and microenvironments play a role in cancer development, progression, and metastasis. Additionally, there is a great need to identify in vitro and in vivo models that more directly emulate specific elements of cancer cells and tumors that restrict the success of our current anticancer approaches. Although a complete cure of cancer is the ultimate goal, it may be more realistic in the near future to treat cancer as a chronic disease using improved drugs and better drug delivery systems.