A Trial of Regorafenib Plus Lorigerlimab in Patients With Locally Recurrent or Regrowing pMMR/MSS Localized Rectal Cancer

Inclusion Criteria: * Histological or pathological confirmation of rectal or anal adenocarcinoma (collectively referred to as "rectal cancer" or "rectal (adeno)carcinoma" throughout this protocol). * MSS or pMMR status as tested according to institutional standard practice. For example, pMMR status can be determined by intact expression by immunohistochemistry of all 4 mismatch repair proteins (MLH1, MSH2, MSH6, and PMS2) while microsatellite instability can be determined by polymerase chain reaction (PCR) or next generation sequencing (NGS). Note: methodologies (e.g., ddPCR, NGS) to determine microsatellite instability on ctDNA are acceptable for study eligibility evaluation. * The evidence of regrowth, confirmed by biopsy, following a near-complete or complete response at least three months following completion of planned total neoadjuvant therapy or locally recurrent disease after total neoadjuvant therapy as treatment for localized rectal cancer at the discretion of the treating provider or PI. * The potential for R0 (complete) resection of the residual cancer at the discretion of the surgeon must be documented. * Willing to undergo pretreatment biopsy of the regrowing or recurrent rectal cancer that can be both safely and effectively biopsied at the discretion of the collaborator. * ECOG performance status of 0 or 1 (APPENDIX A). * Ability to understand, willingness to sign a written informed consent document and compliance with the study procedures. * Ability to swal…