I'm very sorry to hear that you required radiation therapy at such a young age. This is definitely a question that you should discuss with your radiation oncologist
, as they will know the specifics of your case, and be able to give you a more directed answer as to whether this is actually pertinent to you. Since radiation therapy is most commonly used for cancer, I presume this was the case with you (but it doesn't have to be, as there are many other indications for radiation therapy). However, without knowing what kind of cancer you had (or if you even had cancer), or the location, amount of radiation, size of the radiation port, etc I can't give you directed information.
I can give you some general information about radiation therapy...ionizing radiation applies energy that can cause free radicals within cells. Free radicals are atoms or molecules that have unpaired electrons and are very detrimental to the cellular structure and DNA within tissues. Typically resulting in cell death. While the radiation is directed as exactly as possible to target the cancer cells, it will inevitably need to go through some normal tissue, and the effects of the radiation are not exclusive to cancer cells, but present within normal tissues as well. Unfortunately the bodies lymphatics are sometimes within the radiation field, and as a result can be damaged in the attempt to kill the cancer cells (akin to collateral damage). So it is possible to develop lymphedema after radiation therapy due to damaged lymphatic drainage. I have no idea if this is exactly what is going on with you however, so I would definitely recommend discussing your concerns with your radiation oncologist. I hope this helps.