You're hoping for more from your mother than her past
history shows her being able to give. Quite possibly she
has never experienced the type of caring you need. The
situation is akin to being able to sing a song requires
knowing the song.
While your need is very real, once more you will need to
rely more on yourself and others than you can get from
your mother. You realize what you need. Instead of being
overwhelmed by your fear, let it motivate you to talk with
your mother.
On the basis of your present state, mentally you are living
with cancer already. Instead, live while you can and find
the joy that is available. Worry lacks the power to improve
our lives or to save us. What will be, will be and we must
handle each situation if it arises, not before. Keep yourself
open to present comforts and joys.