**1. Introduction**

Every sixth death in the world is due to cancer, making it the second leading cause of death [1,2], and despite survival rates increasing, according to the Institute for Health Metrics and Evaluation of the University of Seattle, more than a million people died because of cancer globally in 2017 [3]. In 2016, more than 8.15 million people suffered from breast cancer, which was the type with the most morbidity, followed by colorectal cancer (CRC) and prostate cancer with 6.32 million and 5.7 million cases, respectively [1]. Of these three cancer types, CRC represents the highest number of deaths [3]. Several factors increase the risk of cancer; however, advancing age is the most important for cancer overall, and for CRC, specifically, a diet rich in meat cooked at high temperatures is associated with an increased risk of CRC [4].

Moreover, moderate-to-heavy alcohol consumption is associated with a 1.2- to 1.5-fold increased risk of CRC [5]. Others factors include African American ethnicity, male sex, inflammatory bowel disease, obesity, a sedentary lifestyle, red meat and processed meat intake, tobacco use, a history of abdominal radiation, acromegaly, renal transplant with use of immunosuppressive medications, diabetes mellitus and insulin resistance, androgen deprivation therapy, cholecystectomy, coronary artery disease, and ureterocolic anastomosis [6].

All of the above have led to a huge interest in cancer research. Today, cancer research is focused on identifying the causes and developing strategies for the prevention, diagnosis, treatment, and cure of cancer [7]. Cancer is one of the most investigated subjects; for instance, the proportion of cancer-related entries in PubMed rose from 6% in 1950 to 16% in 2016 [8], being even higher than for other diseases such as various infections (malaria, AIDS, tuberculosis, among others) and diabetes [8].

Accordingly, there is huge scientific research interest in treating and curing CRC, and several strategies have arisen to improve the therapeutic e ffects and reduce the side e ffects of actual chemotherapy for CRC treatment. Most of them include polymer drug delivery systems. Thus, this paper aims to review polymer drug delivery systems for adjuvant treatments for CRC, including an initial scientific-technological analysis of the papers and patents related to cancer, CRC, and adjuvant treatments using polymer approaches. The novelty of this paper lies in its broad overview of polymer families and the interaction of them with adjuvants. Moreover, it is explained how the behavior of those emerging drug delivery strategies is related to the superficial charge and chemical groups of the used polymers, information that, to the knowledge of the authors, is not reviewed in the literature for CRC.
