I had 5 radiation sessions (hypofractionated) in Nov 2024 (after lumpectomy on right side). By May 2026, my right arm was tight and stiff enough that I mentioned it to my medical oncologist. She said I do not have lymphedema but referred me to lymphedema physical therapy anyway. She said their exercises also work for muscle/ skin tightness. I've started PT once a week and doing the daily exercises. I hope for improvement but expect it to be slow. I'm 82--and sadly, healing is slower as one ages!
Also, I'm not sorry I had radiotherapy. My cancer turned out to be a rather aggressive one--not what is usual in someone my age.