The 42-year-old wife of Prince William is expected to undertake a light program of engagements until the end of the year.
Kate announced in March that she was being treated for an undisclosed type of cancer.
The princess, who has acknowledged that she has good days and bad days while undergoing treatment, last appeared in public for the men’s final at Wimbledon in July.
She appeared moved by the standing ovation she received.
“Life as you know it can change in an instant and we have had to find a way to navigate the stormy waters and road unknown,” she said in the video, which was shot in a forest and included images of the whole family.
“The cancer journey is complex, scary and unpredictable for everyone, especially those closest to you,” she said.
“With humility, it also brings you face to face with your own vulnerabilities in a way you have never considered before, and with that, a new perspective on everything.”
