I am sorry that this is happening and that your dad is sick. Of course this causes you anxiety...it would be weird if it didn't!
Try not to pre-worry about what his test will conclude. It could be that nothing is found and that he will hold steady, or even move in a healing direction. Really there is 2/3 more chance of a neutral or good outcome than anything else.
Use all of your coping skills to help you get through this stressful time.
I am sending prayers for your father, and for you.
"Courage is not the abscence of fear, it is feeling afraid and doing it anyway!"
"Worrying does not empty tomorrow of its troubles...it empties today of its strength."
Corrie Ten Boom
Panic Syndrome recovery due to CBT