Neoadjuvant Fruquintinib Plus Tislelizumab Combined With mCapeOX Versus CapeOX for Mid-high pMMR/MSS Locally Advanced Rectal Cancer

The goal of this clinical trial is to learn if neoadjuvant Fruquintinib and Tislelizumab combined with mCapeOX works to treat mid-high pMMR/MSS locally advanced rectal cancer patients compared with CapeOX. It will also learn about the safety of neoadjuvant Fruquintinib and Tislelizumab combined with mCapeOX. The main questions it aims to answer are: * Does neoadjuvant Fruquintinib and Tislelizumab combined with mCapeOX improve the pCR rate of mid-high pMMR/MSS locally advanced rectal cancer patients? * What medical problems do participants have when receiving neoadjuvant Fruquintinib and Tislelizumab combined with mCapeOX? Researchers will compare Fruquintinib and Tislelizumab combined with mCapeOX to CapeOX to see if neoadjuvant Fruquintinib and Tislelizumab combined with mCapeOX works to treat mid-high pMMR/MSS locally advanced rectal cancer patients. Participants will: * Receive Fruquintinib and Tislelizumab combined with mCapeOX or CapeOX before surgery up to 4 cycles * Receive radical operations and three years follow-up * Keep a diary of their postoperative pathology results and survival