Paradigm Shifts in Perioperative Management of Colorectal Cancer: Personalization Based on Tumor Biology, Primary Site, and Recurrence Risk, and the Evolving Role of Organ Preservation.

Perioperative treatment for colorectal cancer (CRC) is undergoing a paradigm shift from uniform cytotoxic regimens toward strategies guided by tumor location, microsatellite instability (MSI)/mismatch repair (MMR) status, and recurrence risk. Four clinically relevant subgroups now shape decision-making: microsatellite stable (MSS)/proficient MMR (pMMR) colon cancer, microsatellite instability-high (MSI-H)/deficient MMR (dMMR) colon cancer, MSS/pMMR rectal cancer, and MSI-H/dMMR rectal cancer. In MSS/pMMR colon cancer, adjuvant therapy is being refined through risk-adapted treatment duration and selective use of neoadjuvant chemotherapy. In MSS/pMMR rectal cancer, total neoadjuvant therapy, selective omission of pelvic radiotherapy, and watch-and-wait strategies are redefining treatment sequencing and organ preservation. In MSI-H/dMMR colon cancer, immune checkpoint inhibitor (ICI) therapy has shown marked activity in both adjuvant and neoadjuvant settings. In MSI-H/dMMR rectal cancer, neoadjuvant ICI therapy is being explored as a non-operative organ preservation strategy. In parallel, circulating tumor DNA (ctDNA)-based minimal residual disease (MRD) assessment is emerging as a tool for postoperative escalation, de-escalation, and surveillance. Across these settings, the maturity of the evidence varies widely, ranging from established phase III standards to guideline-endorsed but still single-arm approaches and investigational strategies that require prospective validation before routine adoption. This review summarizes the current evidence and remaining challenges in biology-, site-, and risk-adapted perioperative management of CRC.