Kate Middleton, the Duchess of Cambridge, sent a letter to a 9-year-old boy that is battling cancer whom she met during a visit last month to Royal Marsden Hospital.

Kate and Prince William visited Fabian Bate at the hospital in September. In the letter written on St. James Palace letterhead and dated October 13, Kate sends him greetings and praises his belief and positive energy.

“Despite the enormously demanding course of treatment you are undergoing, I was so touched by your strength of character, and delighted to hear the news that one of your big sisters will be able to donate bone marrow to you later this year,” Middleton wrote. ”I will keep my fingers crossed that your health goes from strength to strength over the months ahead.”

“This must be a troubling time for you, your parents and your sisters, but I know I left The Royal Marsden assured by how incredibly talented, kind and clever the team at the hospital are. Combined with your belief and positive energy, you couldn’t be in better hands.”

“Keep up the good work with the blog,” she encouraged Fabian, “and in the meantime I will keep you and your family in my thoughts and prayers.”

Bate's father Darrel, 49, told People Magazine the letter was "a good distraction" for Fabian.

"This is something to talk about with our family and friends," he said. "It's a real morale booster and it was really quite personalized to him and he has something to cherish for years to come."

Fabian was first diagnosed with leukemia in 2006 but relapsed earlier this year. He is awaiting a test this week that will determine if he'll be ready in December to receive a bone-marrow transplant from his sister.