Diem Brown died after a long battle with cancer at age 32 on Friday.
The reality star was originally diagnosed with ovarian cancer in 2003, and relapsed in 2012. Brown discovered she had colon cancer in August, and the disease spread to her liver and lymph nodes. She chronicled her experiences in a blog for People, and remained optimistic about her future.
"I believe in positive thinking, and even more so in the power of striving for seemingly impossible goals," she told the magazine in October. "It's my personal perspective that you live as hard and as vigorously as you can. My goals are something I believe in."
Brown came to fame on MTV reality competition The Challenge in 2006. She first appeared on Real World/Road Rules Challenge: Fresh Meat, and subsequently participated in The Duel, The Gauntlet III, The Duel 2, The Ruins and Battle of the Exes.
"MTV is tremendously sad to hear the news that Diem Brown has lost her long battle with cancer," the network said in a statement. "We send our deepest condolences to her family and friends. Diem was a true fighter and brought passion to everything she touched. We will miss her."
Brown was a patient advocate for those with cancer, and founded website MedGift earlier this year. The site serves as a donation page for patients who are ill, and allows family and friends to contribute funds or specific gifts to their loved one.