The Princess of Wales has shared a major update on her “scary and unpredictable” cancer journey in a highly personal and heartwarming new video featuring her young family.

Catherine, 42, revealed she had finished her months-long course of preventative chemotherapy and was entering a “new phase of recovery”.

The princess also said she would return to some public work later this year. However, she said her path to “full recovery” was not yet over.

“Doing what I can to stay cancer free is now my focus,” Kate said in the video posted to social media on Tuesday (AEST).

“Although I have finished chemotherapy, my path to healing and full recovery is long and I must continue to take each day as it comes.

“I am, however, looking forward to being back at work and undertaking a few more public engagements in the coming months when I can.”

The wife of heir-to-the-throne Prince William said the treatment had given her a new perspective and made her grateful for “the simple yet important things in life which so many of us often take for granted”.

“Of simply loving and being loved,” she said.

Kate says she appreciates the important things in life. Photo: Prince and Princess of Wales

Kate had major abdominal surgery in January that revealed the presence of cancer. She has been having treatment since then.

Her personal message accompanied a video of her with Prince William and their three young children, Princes George and Louis and Princess Charlotte.

It was filmed in Norfolk, eastern England, last month and shows a healthy looking Kate walking through woods with her family and lying on a beach next to William.

In other footage she is shown pushing Louis on a swing and being joined by her parents, Carole and Mike Middleton, as they play a board game.

The family is filmed spending quality time together. Photo: Prince and Princess of Wales

“As the summer comes to an end, I cannot tell you what a relief it is to have finally completed my chemotherapy treatment,” Kate opens her message.

“The last nine months have been incredibly tough for us as a family.

“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.

“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.”

Kate and her family enjoying the simple pleasures. Photo: Prince and Princess of Wales

Kate says she and William are grateful for the global messages of support.

“Despite all that has gone before, I enter this new phase of recovery with a renewed sense of hope and appreciation of life,” she says.

“To all those who are continuing their own cancer journey – I remain with you, side by side, hand in hand. Out of darkness, can come light, so let that light shine bright.”

In June, Kate made her first public appearance since her health issues emerged at Trooping the Colour, the annual military parade to mark the King’s official birthday.

In July, she appeared with daughter Charlotte and sister Pippa Matthews at the Wimbledon tennis championships.

Her office, Kensington Palace, has declined to give any further details about the type of cancer or other specifics about her treatment, other than to say the preventative chemotherapy began in February.