Immunotherapy has achieved significant therapeutic effect in DNA mismatch repair-deficient or microsatellite instability-high (dMMR/MSI-H) colorectal cancer (CRC). MMR expression and MSS status are the important effective factors of immunotherapy. PD-1monocolnal antibody therapy has accessed excellent treatment effect in advanced dMMR/MSI-H CRC and neoadjuvant therapeutic effect in early colon cancer, more than fifty percent of dMMR/MSI-H CRC patients might get pathological complete response(pCR) after PD-1 monoclonal antibody treatment. The treatments had been proved to be safe and the toxicities were controllable. Rectal cancer(RC) is one of the most common malignant tumors in China. So far, radical resection with or without neoadjuvant chemotherapy of chemoradiotherapy are still standard comprehensive treatments recommended to distal RC by NCCN, ESMO and CSCO. For distant RC, radical resection and neoadjuvant chemotherapy or chemoradiotherapy might cause lots of treatment cost,damage to defecation and sexual function, acute toxicity, chronic dysfunction, even loss of anus and psychological disorder. So far, whether watch and wait could be performed in patients with dMMR/MSI-H distal RC accessed pCR after PD-1 monoclonal antibody therapy or not is still not clear. Thus, this study aims to evaluate the effect and safety of watch and wait in patients with dMMR/MSI-H distal RC accessed pCR after PD-1 monoclonal antibody therapy.
Immunotherapy has achieved significant therapeutic effect in DNA mismatch repair-deficient or microsatellite instability-high (dMMR/MSI-H) colorectal cancer (CRC) , more than fifty percent of dMMR/MSI-H CRC patients might get pathological complete response(pCR) after PD-1 monoclonal antibody treatment. For distant rectal cancer(RC), radical resection and neoadjuvant chemotherapy or chemoradiotherapy might cause lots of treatment cost,damage to defecation and sexual function, acute toxicity, chronic dysfunction, even loss of anus and psychological disorder. This study aims to evaluate the effect and safety of watch and wait in patients with dMMR/MSI-H distal RC accessed pCR after PD-1 monoclonal antibody therapy.