Postoperative cancer treatments: In-situ delivery system designed on demand

The keys to the prevention of tumor recurrence after operation are the elimination of residual tumor cells and the reversal of microenvironments that induce recurrence. In the formulation of a treatment scheme, building an appropriate drug delivery system is essential. An in-situ drug delivery system (ISDDS) is regarded as an effective treatment route for postoperative use that increases drug delivery efficiency and mitigates side-effects. ISDDS technology has been considerably improved through a clearer understanding of the mechanisms of postoperative recurrence and the development of drug delivery materials. This paper describes the initiation and characteristics of postoperative recurrence mechanisms. Based on this information, design principles for ISDDS are proposed, and a variety of practical drug delivery systems that fulfil specific therapeutic needs are presented. Challenges and future opportunities related to the application of in-situ drug carriers for inhibiting cancer recurrence are also discussed.