After coming back from cancer and surgery several years ago, Serena Burla was on a roll in 2017. Then she found out she had cancer again...

Serena Burla will run the Boston Marathon in 2018 after coming back from a second bout with a rare form of cancer. But, says her coach, she's as tough and resilient as any person he knows. My story for ESPN.com's Endurance Sports section: http://www.espn.com/olympics/story/_/id/23028557/2018-boston-marathon-resiliency-us-marathoner-serena-burla