British author Sophie Kinsella, best known for her best-selling "Confessions of a Shopaholic" book series, revealed on social media that she has been undergoing treatment for a brain tumor.

Kinsella wrote in the caption for an Instagram post, "To my dear readers & followers, I’ve wanted for a long time to share with you a health update and I’ve been waiting for the strength to do so. At the end of 2022 I was diagnosed with glioblastoma, a form of aggressive brain cancer. I did not share this before because I wanted to make sure that my children were able to hear and process the news in privacy and adapt to our ‘new normal.’"

She continued, "I have been under the care of the excellent team at University College Hospital in London and have had successful surgery and subsequent radiotherapy and chemotherapy, which is still ongoing."

"At the moment all is stable and I am feeling generally very well, though I get very tired," she added, joking, "and my memory is even worse than it was before!" 

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Side by side photos of Sophie Kinsella and Isla Fisher with an inset of the Confessions of a Shopaholic book cover over them

Sophie Kinsella, best-selling author of "Confessions of a Shopaholic," which served as inspiration for the Isla Fisher movie in 2009, announced she has brain cancer. (Getty Image/Random House)

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Kinsella, whose real name is Madeleine Wickham, rose to literary fame with her 2000 novel "Confessions of a Shopaholic." The book kicked off a long-running series, with a total of ten books, the most recent one published in 2019.

Isla Fisher starred in the 2009 film adaptation of the first "Confessions" book, playing financial journalist and shopping addict Becky Bloomwood. Hugh Dancy co-starred as her love interest in the romantic comedy.

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Fisher commented on Kinsella’s post, writing, "Sending you so much love and healing energy."

Isla Fisher, Sophie Kinsella, and Jerry Bruckheimer posing together

Isla Fisher with Kinsella and producer Jerry Bruckheimer at the UK premiere of "Confessions of a Shopaholic" in 2009.  (Ian West - PA Images/PA Images via Getty Images)

The 54-year-old has five children, four sons and a daughter, with her husband, Henry Wickham. 

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She concluded her post, "To everyone who is suffering from cancer in any form I send love and best wishes, as well as to those who support them. It can feel very lonely and scary to have a tough diagnosis, and the support and care of those around you means more than words can say."

"I’ll be in touch soon, and in the meanwhile, greetings from sunny London," she added, referring to the gray skies in the photo she shared in her post.

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Glioblastoma is a rare and fast-growing cancer that starts in the brain, but is the most common type found in adults, according to Cedars-Sinai. Treatments typically involve surgery, radiation, and chemotherapy, and though there is no real cure, they can manage symptoms and help prolong a patient’s life.