She Had One Goal Before She Died: Finish That Last Marathon

“She talked about doing all these marathons around the world,” he said. “She thought, ‘Maybe I could do this.’ She became so focused. It was truly amazing.”

More than a year later, in November 2015, Ms. Seman ran her first marathon, in New York.

“It was something I wished I could do,” she told Runners World. “I just thought, if this was ever something I want to do, I have to do it now. I signed up for it, and I was like ‘What did I just do?!’ I was freaking out.”

Chicago followed in 2016, Boston in 2017 and Berlin in 2018.

In 2019, Ms. Seman ran her last two marathons, in Tokyo and London, eight weeks apart. This required her to train as much as she could while undergoing chemotherapy.

Ms. Seman did not pause or panic. Instead, after Berlin, she began working with Daphne Matalene, 46, a running coach.

“Even when you are super healthy and super trained it still takes a lot out of you,” said Ms. Matalene, who has run five of the six marathons. “Renee was totally undeterred by that. Her goal was not to win; it was not even to run her fastest.”

Ms. Matalene came up with a training regimen that worked around Ms. Seman’s treatment schedule. Ms. Seman would run easy miles in the morning and then have chemotherapy treatment in the afternoon. Days later, once she had recovered, she would do a long run of 12 to 16 miles.

Many runners who try to complete the six races are dealing with health issues or recently had a health scare, said Lorna Campbell, a spokeswoman for the Abbott World Marathon Majors.