You might want to look up "Beansmama". She was diagnosed with Stage IV colon cancer. Every traditional chemo regiment failed her, she was months away from death. As a last attempt, they put her on Keytruda, and it was successful in shrinking her tumors in her liver to get her to surgery. She had a very major surgery and survived it. The tumor they removed was dead. She passed a few months later, not from cancer butt rather a blood clot. What is important, she died cancer free and she would have been very proud of that fact.
Because of her and people like her, Keytruda, I believe, has been approved by the FDA for colon cancer patients.
There are a few others around here, hopefully they will chime in soon,