The singer, who is an ambassador for Breast Cancer Care, told the Evening Standard that her aunt Jean lost an eight-year battle against the disease in 2009.
Burke said: "My auntie Jean had breast cancer. She died in my arms in hospital. We were there for her very last moments.
"I really do this because of her. It was a life-changing moment for my family. I just want to do my part to give back."
Burke will perform at the Girls' Night Out charity concert hosted by Asda at Shepherd's Bush Empire on January 12 to mark 15 years of the Tickled Pink campaign.
Other stars booked for the show include The Saturdays, Little Mix, Chipmunk and Dionne Bromfield.
In 2010, Burke walked the Inca Trail in a trek organised by Denise Van Outen and Fearne Cotton to raise money for Breast Cancer Care.
The X Factor winner also performed with 1,500 schoolchildren as the headliner of the CLIC Sargent and Young Voices fundraiser at the Royal Albert Hall later that year.
Watch Alexandra Burke's video blog before she set off on her Inca Trail below: