It took a few years but eventually I tapered off the gabapentin. For breakthrough pain I use a Norco- an Rx of 30 lasts me 6-8 months. I also have pain from collapsed vertebrae that healed wrong or I might use it less.

Remember, we are the patients for whom these meds were developed. Pain causes interference with healing rest. You don't have to be on them forever.

If there is a Livestrong program at your local YMCA ask your oncologist about clearance to participate. The trainers have extra education to help them modify exercise especially for your needs. I found that strengthening the muscles that hold the ribs in place and support breathing helped me reduce my pain meds.
Best hopes!