The main goal of this study is to test a new treatment approach for colon cancer. The treatment involves dostarlimab along with a specific type of chemotherapy called CAPEOX (short for "capecitabine + oxaliplatin") to check if using these two together works better than using just CAPEOX by itself. This treatment is given before any surgery takes place; a method referred to as "neoadjuvant therapy." . The aim is to see if this new approach can show early signs of effectiveness in treating participants with a specific type of colon cancer known as mismatch repair proficient/ microsatellite stable (MMRp/MSS), where the cells have normal repair systems and stable DNA sequences. This study will also look at specific signs in the blood and tumor to see if they can help predict how well the treatment is working. This could help better understand how dostarlimab contributes to the response of the disease to treatment.
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-
MMR status: MMR status must be assessed by Immunohistochemistry (IHC) for MMR protein expression (MLH1, MSH2, MSH6, PMS2) where all proteins are present indicates MMRp; MMR status may be determined local laboratory; or
Has distant metastatic disease
Has received prior medical therapy (chemotherapy, immunotherapy, biologic, or targeted 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 has any 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., myasthenic syndrome/myasthenia gravis, encephalitis, Guillain Barré Syndrome, or transverse myelitis), exfoliative dermatitis of any grade [Stevens-Johnson Syndrome (SJS), Toxic Epidermal Necrolysis (TEN), or Drug rash with eosinophilia and systemic symptoms (DRESS) syndrome], or myocarditis of any grade. Non-clinically significant laboratory abnormalities are not exclusionary
Parallel
Dostarlimab
Biological/VaccineDostarlimab will be administered.
CAPEOX
DrugCAPEOX chemotherapy consisting of capecitabine and oxaliplatin will be administered.
Major pathological response (mPR) rate
mPR rate is defined as the proportion of participants with ≤10% residual viable tumor (RVT) value in the surgical resection sample as determined by local assessment.
Number of participants with adverse events (AEs), serious adverse events (SAEs), immune-mediated adverse events (imAEs), and AEs leading to death or discontinuation of study intervention
Percentage of participants for whom primary tumour resection is not excluded
Complete pathologic response (cPR) rate
cPR rate is defined as the proportion of participants with 0% RVT value in the surgical resection sample as determined by local assessment.
Major pathological response excluding cPR rate
mPR rate is defined as the proportion of participants with ≤10% RVT value in the surgical resection sample as determined by local assessment. cPR rate is defined as the proportion of participants with 0% RVT value in the surgical resection sample as determined by local assessment.
Partial pathologic response rate
Partial pathologic response rate is defined as the proportion of participants with \>10% and ≤50% RVT value in the surgical resection sample as determined by local assessment.
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