For most families, a diagnosis of cancer or other serious illness represents a crisis. Family members find that they must adjust not only to the diagnosis, but also to a prolonged period of treatment. This presents a major challenge to both parents and children.
Talking to children about illness can be a very difficult thing to do, and may be upsetting for both you and the child. However, involving children in the situation and letting them know what is happening can be very supportive to them and can help both them and you to cope better with the illness.
Children can sense when something is wrong because they are very sensitive to tension and stress. If you try to protect them by saying nothing, they may fear that something even worse is happening. Ideally talk to your children as soon as possible after diagnosis. In this way you determine what information they know.
And remember: there are no absolute rights or wrongs. Like most of parenting, the actual words you use are not as important as letting your children know that you are there for them, and that they can bring their questions and fears to you. You may even find that as you talk about your illness, you and your children develop a closer connection that strengthens your discussions about other issues. Each family finds its own unique way to adjust. You will find yours.