I am confused about buprenorphine?

Buprenorphine is definitely a pain killer and it is very difficult to get prescribed because it is an opioid drug. Doctors are afraid to prescribe it for fear of being challenged and losing their license, so your cancer team is definitely trying to help with your pain. You should be grateful that they are trying to help you with this drug. I don’t know whether you are getting buprenorphine by pill or patch. And what dose are you getting? I had a stroke which caused severe 24/7 migraines. My migraines were so severe that I was too nauseated to eat and lost 1/3 of my weight in just 3 months. About every 3 weeks the pain would be intolerable with vomiting for hours. Then I would have to go to the ER. My neurologist hated the intense medications that I would be given. When the buprenorphine patches, then called Butrans, came on the market, he prescribed 15 mcg patches for me. Then I never had to go to the ER again. What an incredible drug. There are some strong side effects, but it was definitely better than that pain.
In the pill form of it, I got some bad side effects that were intolerable. Since then I had a bad reaction to my antidepressant, an SSRI, and had to get off it. My neurologist couldn’t answer why I no longer needed an antidepressant for the past 5 years when I was told that I would always need it. I was trying to get off of buprenorphine because I was getting a newer migraine medication that controlled my migraines fairly well. But I had stroke leg pain at night that my PT could not help it. I had great difficulty sleeping because of it. Plus I was getting depressed. In researching buprenorphine, I found that low levels could successfully treat hard to treat depression in a matter of days. So when I went back to 7.5 mcg, the depression was gone and my stroke leg no longer hurt. What a wonderful drug for me at 7.5 mcg.
I do hope that it relieves your pain. Pain is a very disabling thing to live with. If not, maybe you need a higher dose. I got lung cancer this winter, so I am struggling with side effects from radiation treatments. So I also feel for you since you also have cancer.
I do wish you the best. Sara