Greetings, is it true that red meet is not good for cancer patients, who are taking chemotherapy ? if yes then why ?

I've never: Heard of that but it could have something to do with one specific chemotherapeutic medication. If you are on one talk to your oncologist.

Undercooked meat?: I can think of no chemotherapies that would be adversely affected by the consumption of red meat. The only thing i can think of is patients on chemo can become quite immunosuppressed, thus they should not consume items that pose a greater than average risk for infection, such as undercooked red meat.