This is misleading. Yes, the response rate is extremely high but all of this patients shared a mutation or a group of mutations in mismatch repair proteins (they were all MMR deficient, or mismatch instability high).
If I had to guess this is a huge marketing plot to bring yet another extremely expensive drug to the market. What is happening is that different drugs (ie different companies) take the space of a specific tumor (Keytruda for lung, Opdivo for melanoma, Tecentriq for liveer cancer) and Dostarlimab is going to claim the rectal cancer space.
This effect is shared across many tumors with this feature not only rectal and the FDA approved a drug with the same exact mechanism in 2017 (https://www.fda.gov/drugs/resources-information-approved-dru...)
If I had to guess this is a huge marketing plot to bring yet another extremely expensive drug to the market. What is happening is that different drugs (ie different companies) take the space of a specific tumor (Keytruda for lung, Opdivo for melanoma, Tecentriq for liveer cancer) and Dostarlimab is going to claim the rectal cancer space.