The reality TV star was first diagnosed with stage-three breast cancer a few months after she wrapped Survivor, and opted for a modified, radical bilateral mastectomy, followed by courses of chemotherapy and tamoxifen, a drug used to prevent recurrence.
"In the summer of 2004, I felt something in my right breast that didn't feel normal," Lyon told PEOPLE in October 2005. "I thought it was probably scar tissue related to my breast implants. So I let it go – for a long time."
Being on the CBS competition boosted her spirits and provided an inner strength to battle her disease. "Survivor taught me there's an end in sight," she told PEOPLE. "As hard as it is, it will be over, and you have to appreciate every day."
Survivor host Jeff Probst said that "near the end" he and Lyon spoke "about the idea that death is such a hard subject and so many of us simply don’t know what is appropriate to say, so we end up saying the wrong thing for all the right reasons."
"If I learned anything from Jenn it is this: Don’t be afraid to ask someone how they are truly feeling about dying," Probst says. "Don’t shy away from the scary parts of death. They need someone to talk to about what is going on inside their head. Most importantly, encourage them to let go of the expectations of others and give them permission to do what is right for them, even if it means letting go"
Her Survivor castmates remember her as kind and courageous. "She is the model of grace, and has been so brave," fellow contestant Ian Rosenberger told PEOPLE at the Survivor 10th anniversary party on Jan. 9.
Despite her illness, Lyons hosted many fundraisers for breast cancer research. Most recently, she opened a Christmas tree lot with proceeds designated to her cause.
With reporting by CYNTHIA WANG