Angelina Jolie's fiance Brad Pitt has praised her for her "heroic" decision to undergo a double mastectomy in a bid to thwart breast cancer.

The actress revealed on Tuesday that she had undergone the surgery earlier this year after learning that she was a carrier of the BRCA1 gene -- a "faulty" gene that gave her an 87% chance of developing the cancer.

Jolie had the surgery in February and managed to keep it a secret for months until penning an article for the New York Times to share her story.

"My chances of developing breast cancer have dropped from 87 percent to under five per cent. (Now) I can tell my children that they don't need to fear they will lose me to breast cancer. I feel empowered that I made a strong choice that in no way diminishes my femininity," she wrote. "For any woman reading this, I hope it helps you to know you have options. I choose not to keep my story private because there are many women who do not know that they might be living under the shadow of cancer."

Pitt released a statement after his fiancee's revelation, thanking her for being brave enough to make the difficult decision.

"Having witnessed this decision firsthand, I find Angie's choice, as well as so many others like her, absolutely heroic," he told the London Evening Standard. "I thank our medical team for their care and focus. All I want... is for her to have a long and healthy life, with myself and our children. This is a happy day for our family."

Jolie's family history played heavily on her decision -- the actress's mother, Marcheline Bertrand, died after nearly a decade-long battle with ovarian cancer. She was 56.

"I want to encourage every woman, especially if you have a family history of breast or ovarian cancer, to seek out the information and medical experts who can help you through this aspect of your life, and to make your own informed choices," Jolie said in her article.

Jolie's brother James Haven and future mother-in-law Jane Pitt also voiced their support for the actress.

"I am so grateful to be her brother," said Haven; while Pitt's mother Jane said, "We're so very proud of Angie, this means so much to our family, especially our grandchildren. We love her dearly."