Armstrong resigned from the board of directors for Livestrong on Nov. 4. He had resigned Oct. 17 as chairman from the charity he founded but had kept a seat on the board.
The U.S. Anti-Doping Agency ordered Armstrong banned from the sport for life and stripped of his titles. The International Cycling Union, which had originally supported Armstrong's fight, later agreed to wipe out Armstrong's record seven victories.
Livestrong spokeswoman Katherine McLane said Monday that Armstrong "remains the inspiration" and is still its largest donor with nearly US$7 million over the years.
In a statement, new board chairman Jeff Garvey said Armstrong resigned from the board to spare the organization any negative effects resulting from the controversy surrounding his cycling career.
"Lance Armstrong was instrumental in changing the way the world views people affected by cancer. His devotion to serving survivors is unparalleled and for 15 years, he committed himself to that cause with all his heart," Garvey said.
Armstrong has not commented publicly on the USADA report and recently returned to Austin from Hawaii. Over the weekend, he posted a photograph on Twitter in which he is lying on a couch at his home with seven yellow Tour de France jerseys mounted on the wall.
Armstrong also has lost his personal sponsors, including Nike and brewing giant Anheuser-Busch, who dropped their contracts with him or said they would not renew when current deals expire.
Garvey said the foundation would continue to expand free services to cancer survivors and advocate on their behalf.
"Because of Lance, there is today more focus on the individuals whom this disease strikes, and on healing the person, not just killing the disease," Garvey said.
USADA's report accused Armstrong of helping run "the most sophisticated, professionalized and successful doping program that sport has ever seen" within his U.S. Postal Service and Discovery Channel teams.
The USADA report said Armstrong and his teams used steroids, the blood booster EPO and blood transfusions. The report included statements from 11 former teammates who testified against Armstrong.
Armstrong denies doping, pointing to hundreds of passed drug tests. But he chose not to fight USADA in one of the agency's arbitration hearings, saying the process was biased against him. Former Armstrong team director Johan Bruyneel is also facing doping charges, but he is challenging the USADA case in arbitration.