The Mayo Clinic has received its largest donation from a living person -- a $100 million gift that will be used to establish two innovative cancer-fighting centers. The donation comes from Iowa businessman and philanthropist Richard O. Jacobson, who also is a longtime patient and benefactor of the Rochester institution. "I've been very fortunate, made a lot of money, and I have no family," Jacobson told reporters at the announcement on Thursday. "I always wanted to do something for Mayo Clinic." Mayo plans to use the money to build facilities in Rochester and Phoenix to treat cancer tumors using proton beam therapy. The treatment is considered a better alternative to conventional radiation because the beam targets tumors more precisely, with fewer side effects, Mayo CEO John Noseworthy, MD, said.