In a St. Joseph Healthscene report, researchers warn America needs more cancer specialists. According to a new report, the U.S. will face a shortage of more than 4,000 oncologists by 2020. Two primary factors are driving the deficit. First, the U.S. population is aging - the number of Americans 65 and older is expected to almost double within the next 20 years. Second, oncologists, as a group, are older and closer to retirement than most other doctors.