The Boy in 7 Billion by Callie Blackwell & Karen Hockney

At the age of 10, Deryn Blackwell was diagnosed with Leukaemia.
Then, 18 months later, he developed another rare form of cancer called Langerhan’s cell sarcoma. Only five other people in the world had it at the time. He was the youngest of them all, and the only person in the world known to be fighting it alongside another cancer…