Sheila McGuirk had three children younger than 8 when she was told that her entire colon needed to be removed because of cancer. The news was devastating to McGuirk, an associate professor of veterinary sciences at the University of Wisconsin-Madison, but after two surgeries she is cancer-free. In the eight years since, McGuirk, 52, has become such an accomplished cyclist that she has been picked as one of the 20 to ride cross country, from Los Angeles to Washington, D.C., in the Bristol-Myers Squibb Tour of Hope.