What is the fine-grained topic of the following text: Head and Neck Cancer (HNC) patients—comprising an estimated 65,000 newly diagnosed cases in the U.S. alone in 2017, and an estimated 700,000 worldwide (source: GLOBOCAN)—are at the greatest risk of developing OM (a 90 to 100 percent rate of occurrence). Only return the topic.
Risk of developing OM in Head and Neck Cancer patients