Despite a long battle with cancer, Dr. Moses Christian kept up a remarkable streak of marathons; now, however, it appears Sunday's L.A. Marathon could perhaps be his last

In 1993, Dr. Moses Christian took up running. The next year, he did his first marathon -- and also learned he had prostate cancer. Over two decades, he's continued to run while treating his cancer in a holistic manner. Recently, however, the cancer has spread. But Christian is determined to do Sunday's Los Angeles Marathon. My story for ESPN.com: http://espn.go.com/sports/endurance/story/_/id/10562285/endurance-sports-cancer-keep-81-year-old-runner-los-angeles-marathon