I would push for a med change. Most of us used Duragesic, 72 hours time release patches. Additionally, I had morphine sulphate for breakthrough pain. I am surprised that her MO isn't managing the medications.
Most people go through an adjustment period when starting out on long term opioids. Make sure that she is closely watched - meds, fluid and nutrient intake, assistance to the bathroom, etc.
If she has no MO here is a link to the NCCN Oncology Practice Guidelines for pain management - print and give him a copy.
http://www.nccn.org/professionals/physician_gls/PDF/pain.pdf The pain will get worse for at least a few more weeks due to the residual effect of the radiation.
Pain management is a basic patient right - DEMAND IT!