I'm sorry to hear of your wife's illness. Please pass on to her my admiration and encouragement for fighting the cancer and being alive. This, from a fellow patient (melanoma) whose cancer is inactive at this time. Give her a hug for me and tell her, "Well done; hang in there!"
As to having firearms seized upon being diagnosed with a life threatening illness in America...no, absolutely not! The Second Amendment to our Constitution makes no allowance for forfeiture when one is diagnosed with any medical problem. No certificate or permit is required to purchase and/or own a firearm. Our Founding Fathers determined that "keeping and bearing arms" is one of the inalienable rights granted by our Creator. The Second Amendment prohibits the government from denying its citizens that right, current liberal legislative and judicial efforts notwithstanding.