Restore intestinal steady-state: new advances in the clinical management of chemotherapy-associated diarrhea and constipation.

Chemotherapy remains the primary therapeutic strategy for most tumors, particularly those at advanced stages with distant metastases and resistance to molecularly targeted therapy or immunotherapy. There are many manifestations of chemotherapy-induced gastrointestinal toxicity (CIGT), including chemotherapy-induced diarrhea (CID) and chemotherapy-induced constipation (CIC). Although the World Health Organisation and the International Association Against Cancer have different grading criteria and strategies for the prevention and treatment of CIGT, there are still many unanswered questions that need to be clarified. This review critically describes pathological mechanisms and clinical research, analyzing the variability in diagnostic criteria and the absence of standardization in grading severity. We identify a critical gap in understanding the molecular underpinnings of CID and CIC and suggest targeted areas for future research, including developing personalized treatment approaches based on genetic profiling. The findings suggest a comprehensive treatment approach combining pharmacological and non-pharmacological strategies to enhance life quality and treatment adherence. This review will offer a comprehensive bird-eye of pathophysiological mechanisms, clinical manifestations, and therapeutic strategies of CIGT, thereby enriching accessible references to clinicians, and helping them to prevent and control CID and CIC.