Gaber, who is a professor of genetics, rang the bell at the Advocate Illinois Masonic Center for Advanced Care in Chicago to celebrate completing his prostate cancer treatment.
The hospital said he underwent a combination of therapies for the disease, which runs in his family and claimed the lives of his father, grandfather and one of his uncles. Two of his uncles and his brother are prostate cancer survivors.
Thursday also happened to be Gaber's 68th birthday.
He said he is excited for the future, which includes welcoming his first grandchild in a couple of weeks.