I had a similar pain around the lower rib cage and found myself shallow breathing and living on endone for the pain. My GP couldn't figure out what the pain was from. I did some research myself and found out that the muscles between the ribs can contract from the radiotherapy and restrict movement and cause pain. I found a cancer specialized physiotherapist who even after one session helped to teach me specific rib stretching exercises and how to breath again. The pain subsided completely after about 5 sessions and I was able to ditch the pain meds altogether. Google 'PINC and STEEL cancer rehabilitation' for one nearest you.near you. Hope this helps.
