Once you reach a certain age, you think more about the time that's behind you than what's in front of you. And you know what else is behind you? Your colon. Colorectal cancer is highly treatable, but only if discovered early. Once you hit 50, you should get tested for colon cancer regularly. And even if 50 is still a ways away, you probably have a loved one in the danger zone -- give 'em a reminder to get it checked out. March is Colon Cancer Awareness month, and to help raise awareness about the efficacy of early testing, the St. Louis Undy Run/Walk invites you either to compete in the 5K run or 1-mile fun run to help raise money for the Colon Cancer Alliance. You don't have to strip down to your underwear to participate, but all racers and fun-runners receive a free pair of boxers with their registration. The St. Louis Undy Run/Walk starts at 9 a.m. today at Forest Park in the Lower Muny parking lot (www.undyrunwalk.org). Registration is $35 to $40.