Progress in transdermal drug delivery systems for cancer therapy

Transdermal drug delivery is an appealing option except for oral and hypodermic administration. With the advancement of skin penetration strategies, various anticancer therapeutics ranging from lipophilic small-molecule drugs to hydrophilic biomacromolecules, can be administered transdermally, offering an optional regimen to treat skin cancers. In addition, the activation of the skin immune systems can also assist the treatment of distal sites. Current approaches on enhancing the transdermal delivery efficacy of anticancer drugs are summarized in this review. We also survey recent advances in micro- and nanotechnology-based transdermal formulations for cancer treatment, such as chemotherapy, gene therapy, immunotherapy, phototherapy and combination therapy. New penetration enhancers, materials, formulations and their hypothesized mechanisms for transdermal delivery are highlighted. Advantages and limitations regarding the state-of-the-art transdermal delivery technologies, as well as future perspective are also discussed.