A Study of Neoadjuvant Dostarlimab Plus Capecitabine Plus Oxaliplatin (CAPEOX) Vs CAPEOX With Previously Untreated T4N0 or Stage III Mismatch Repair Proficient (MMRp)/Microsatellite Stable (MSS) Colon Cancer

Inclusion Criteria:

• Has untreated pathologically confirmed colon adenocarcinoma

• Has resectable colon adenocarcinoma defined as clinically T4N0 or Stage III

• Has a tumor demonstrating the presence of either-

1. MMR status: MMR status must be assessed by Immunohistochemistry (IHC) for MMRprotein expression (MLH1, MSH2, MSH6, PMS2) where all proteins are presentindicates MMRp; MMR status may be determined local laboratory; or

2. MSS or Microsatellite Instability-L (MSI-L) phenotype as determined bypolymerase chain reaction (PCR) or by tissue next generation sequencing (NGS),determined by local laboratory

• Provides fresh tumor tissue obtained during either the pre-screening or screeningperiod via colonoscopy performed per procedure manual. Tissue biopsy is required

• Is willing to use adequate contraception male and/or female participants

• Has an Eastern Cooperative Oncology Group - Performance status (ECOG-PS) of 0 or 1

• Has adequate organ function

Exclusion Criteria:

• Has distant metastatic disease

• Has received prior medical therapy (chemotherapy, immunotherapy, biologic, ortargeted therapy), radiation therapy or surgery for management of colon cancer

• Has, in the investigator's opinion, a tumor that is not amenable to surgery or hasany other contraindication to surgery

• Has experienced any of the following with prior immunotherapy: any imAE ≥ Grade 3,immune-mediated severe neurologic events of any-grade (e.g., myasthenicsyndrome/myasthenia gravis, encephalitis, Guillain Barré Syndrome, or transversemyelitis), exfoliative dermatitis of any grade [Stevens-Johnson Syndrome (SJS),Toxic Epidermal Necrolysis (TEN), or Drug rash with eosinophilia and systemicsymptoms (DRESS) syndrome], or myocarditis of any grade. Non-clinically significantlaboratory abnormalities are not exclusionary

• Has any history of interstitial lung disease or immune-related pneumonitis

• Has a history or current evidence of any medical condition, therapy, or laboratoryabnormality that might confound the study results, interfere with theirparticipation for the full duration of the study intervention, or indicate it is notin the best interest of the participant to participate, in the opinion of theinvestigator

• Is considered, in investigator's opinion, a poor medical risk due to a serious,uncontrolled medical disorder, non-malignant systemic disease, or active infectionrequiring systemic therapy

• Has received treatment with an investigational agent within [4 weeks] of the firstdose of study intervention

• Is pregnant or breastfeeding

• Has a history of severe allergic and/or anaphylactic reactions to chimeric, human,or humanized antibodies, fusion proteins, or known allergies to dostarlimab, or itsexcipients, or any components of CAPEOX