Many people cope with their diagnosis by not wanting to talk about it.
If that is the way you feel, then tell this to the people around you, say that you would prefer not to talk about your illness, at least not for the time being.
Sometimes, however it can be the other way round. You may find that it is your family and friends who are denying your illness. They appear to ignore the fact that you have cancer. They may also play down your worries or your symptoms and keep changing the subject.
This can be upsetting, because you want them to support you and understand what is happening to you. In this case start perhaps by saying that you do know what is happening, and that it will help you if you can talk to them about your illness.