Armstrong answered his doubters by winning the race's prologue, which earned him the right to wear the prized yellow jersey during the first stage. He was the overall leader going into the ninth stage, and still people questioned whether he was strong enough to hold off competitors as the race moved into the Alps. But he took the ninth stage and kept the overall lead at the end of the two crucial mountain stages. As the race enters its final week, Armstrong's lead continues to grow.

In less than three years, Armstrong has beaten the odds by surviving cancer and becoming the odds-on favorite to win the Tour de France, riding for the US Postal Service team.

In October 1996, the cyclist learned he had testicular cancer that had spread to his abdomen, lungs, and brain. He was given a 50 percent chance of survival and had surgery to remove his right testicle and brain lesions, followed by three months of chemotherapy.

In 1997, Armstrong was declared cancer-free, and he began his cycling comeback in May 1998. "I was a halfway dead man just a few years ago and the best doctors in the world put me back together," he said during a press conference after winning the ninth stage of the Tour. "I feel better now than ever before."

Caught early, 95 percent of men with testicular cancer are eventually cured. "It's a great success story for modern western medicine," said Gabe Feldman, MD, director of colorectal and prostate cancer for the American Cancer Society (ACS). "It wasn't long ago that testicular cancer was a uniformly fatal diagnosis."

Although testicular cancer is rare, it is the most common cancer among American men aged 15 to 35. For most men, the clearest symptoms are changes in the testicles, such as one becoming larger or firmer than the other, said Dr. Feldman.

Armstrong serves as a visible reminder to young men that the disease can strike even the most physically fit. "Testicular cancer is one those cancers which are highly treatable," Feldman said. "For young men it's not a death sentence. Some men have symptoms, but choose to ignore them because they just don't want to know, or figure if they have it there is nothing they can do. The lesson here is take the first step and find out that there are successful treatments."

No one understands this more than Armstrong. Since his diagnosis, he has founded the Lance Armstrong Foundation to raise money and awareness of urological cancers. After winning the eighth stage of the Tour, he was asked to explain his recovery. "There are no secrets," he said in an ESPN report. "I was sick as a kid could be. It was one of the worst cases my doctors had ever seen - and they were the best."

The ACS estimates that about 7,600 new cases of testicular cancer are reported annually in the US. An estimated 400 men will die from the disease each year.