In her decade of living and running with cancer, last year was Carol Chaoui’s toughest yet. But in 2019, she’s mounted a remarkable comeback. She has stage 4 breast cancer and stage 4 thyroid cancer, but Chaoui, now 56, finished the New York City Marathon on November 3 in 5:39:34—faster than 13-minute pace—even though she has tumors all over her body, including in her brain. And she mostly walked for the last 19 miles after stumbling several times in the early going. “I’m a pretty fast walker,” she quipped after the race. Chaoui was first diagnosed with breast cancer in...