Study of Perioperative Dostarlimab in Participants With Untreated T4N0 or Stage III dMMR/MSI-H Resectable Colon Cancer

To join this study, you need to have colon cancer that has been diagnosed recently and hasn't yet been treated. The cancer must be a specific type that doctors call 'T4N0' or 'Stage III', which means it's still contained in the colon and hasn't spread to distant parts of your body. Importantly, your cancer must have a special genetic marker called dMMR or MSI-H, which the doctors will check for. You also need to be at least 18 years old.

There are several reasons why you might not be able to join. For example, if your cancer has already spread to other organs (like your liver or lungs), or if you've already had treatment for this cancer (like chemotherapy, radiation, or certain surgeries). You also can't join if the cancer is causing a severe blockage that needs immediate surgery, or if you've recently had a major operation. Conditions like certain lung problems (interstitial lung disease, pneumonitis), severe liver disease, or a history of organ transplants would also prevent you from joining. If you are pregnant, breastfeeding, or planning to become pregnant, you cannot take part.

If you decide to take part in this study, you would receive either the new drug (dostarlimab) or a standard chemotherapy treatment (CAPEOX or FOLFOX), usually given before or after your surgery for colon cancer. The specific schedule and number of treatments would be explained in detail by the study team. You would need to attend regular appointments at the clinic for treatment, blood tests, and check-ups to monitor your health and how the treatment is working. This will likely involve scans and other tests. The exact number of visits and the full duration of your participation would depend on which treatment group you are in and will be detailed by the study team, but typically, studies like this involve follow-up for several years.