Armstrong appeared in Austin at a gala for the Lance Armstrong Foundation and told the audience the mission is "bigger than me."
"We will go forward," said Armstrong, who created the foundation in 1997 during his own cancer battle. "There's 28 million people around the world who need us."
Armstrong was stripped of his seven Tour de France championships after a long battle over allegations he used performance-enhancing drugs. He stepped down as chairman of the foundation, but promised to remain active in its fundraising efforts.