Chemoprevention is the use of natural or synthetic substances to prevent、suppress or to reverse the development of colorectal cancer.Aspirin and cox-2 inhibitor are the most effective preventive agents.However,the gastrointestinal and cardiovascular adverse effects limit the application.Recurrent adenomas can be markedly reduced by a combination of difluoromethylornithine and sulinclac and with few side effects.5-aminosalicylate and ursodeoxycholic acid have become the focus of inflammatory bowel disease.The double roles of folate need further study.Statins and EGFR inhibitors have some effects,which are in early clinical studies.The article reviews the new progress of chemoprevention of colorectal cancer.

Objective:To investigate the characteristics of primary catheter malposition (PCM) following totally implantable venous access port (TIVAP) implantation via the internal jugular vein (IJV) and management strategies.Methods:Clinical data of 587 consecutive breast cancer patients undergoing TIVAP implantation via the IJV performed by single team at the Department of Breast Surgery, the First Affiliated Hospital of Zhengzhou University from Aug 2017 to Aug 2022 was retrospectively analyzed.Results:A total of 593 TIVAP were implanted and PCM was found in 18 cases (3.0%). Four hundred and twenty five TIVAP were implanted via the right IJV with one PCM case (0.2%). One hundred and sixty eight TIVAP implantations were performed via the left IJV and PCM occurred in 17 cases (10.1%). The interventional management with a pigtail catheter was performed as a first-line strategy in 11 of the 18 PCM cases, with a success in 10 cases and failure in one. Three cases were successfully managed with the digital subtraction angiography (DSA)-guided open approach. Four cases underwent blind open procedure firstly and 2 suffered a failure.Conclusions:A higher incidence of PCM is found in TIVAP implantations via the left IJV than the right one. The interventional management with a pigtail catheter or the DSA-guided open procedure proves to be feasible for the correction of PCM.