I understand your concern about your mother's pain medication. I remember thinking about my mother "with all of her problems with bone cancer, the last thing she needs is an addiction to pain pills". So my mother and I took our concerns to her oncologist.
Her doctor told her that addiction to pain pills was the least of her problems and not to worry about it. She DID take them and I'm so grateful that she did.
Mother would wake up in the middle of the night. Her pain would be so bad that she would sit in a chair, rock back and forth with her eyes closed, and her hands would shake uncontrollably. I would put a pain pill in her mouth, and a few sips of water. Within 20 minutes she could go back to bed and sleep.
There's no doubt in my mind that if she didn't have that pain medication, the only sleep she would get would be passing out from sheer exhaustion. Eventually the pain would have been so bad that she would have screamed without medication...no doubt in my mind. No one, within hearing distance, would have had any quality of life at this point, least of all my mother.
I drove her to the emergency room once, when the medications didn't work. When we got to the hospital, the admitting staff was putting us through the procedure as though we had the luxury of time. My mother told me to tell one of the women to come to her wheelchair. I was surprised that the woman complied (they were SOOO busy!). My mother couldn't even look at her. She just said "if you don't bring me a shot for my pain immediately, I'm going to start screaming at the top of my lungs".
I told the woman who my mother's doctor was, and one of his nurses was there in 5 minutes with my mother's shot. It was a huge hospital, so I'm sure that some running was involved. A bone scan showed that three of my mother's vertebrae had collapsed.
The pain medications let her have periods of peace and some semblance of a normal life, when there was nothing peaceful or normal about it. She and I could talk about recipes and watch TV together and she could laugh with my children. I'm grateful for those memories from such a horrible, bleak time in our lives. Her doctor was right...opioid addiction WAS the least of her problems.
Mother died a few months later. This was over twenty years ago and I know cancer treatment and medication has improved a lot since then. I had to go through it again with my brother less than 5 years ago, except his was lymphoma instead of breast to bone cancer.
Cherish this time with your mother. Let her grab any comfort her doctor will prescribe for her.
Put each of your hands on your opposite shoulder, close your eyes, and feel the hug I'm giving you. Bless you dear. Please stay in touch.