[Progress in neoadjuvant immunotherapy for locally advanced rectal cancer]

Neoadjuvant chemoradiotherapy (NACRT) is the standard treatment for locally advanced rectal cancer (LARC), yet the pathological complete response (pCR) rates remain suboptimal. The introduction of immunotherapy has opened new avenues for LARC management, particularly in patients with mismatch repair deficiency (dMMR) or microsatellite instability-high (MSI-H) status. In this subset, anti-programmed cell death protein-1 (PD-1) monoclonal antibodies demonstrate marked efficacy, achieving high rates of clinical complete response (cCR) and pCR, thereby facilitating non-operative watch-and-wait (W&W) strategies. However, long-term outcomes and large-scale validation are still awaited. Conversely, in patients with LARC who have proficient mismatch repair (pMMR) or microsatellite stability (MSS), PD-1 inhibition alone shows limited benefit. Current research thus focuses on combinatorial approaches. Combining immunotherapy with chemoradiotherapy has shown promise in improving pCR rates in pMMR/MSS LARC, without significantly exacerbating severe adverse events. However, the discordance between post-treatment imaging assessments and pathological findings complicates clinical decision-making. Future directions include optimizing immune checkpoint inhibitor (ICI) regimens for pMMR/MSS LARC, with ongoing investigations into dual immunotherapy and anti-angiogenic synergism. Additionally, biomarker discovery, which is leveraging multi-omics and artificial intelligence (AI), will be pivotal in achieving precision therapy that balances short-term efficacy with long-term survival benefits.