Ethan and Jenna just before the race
Zohn, 37, began training for this year's race immediately after he and girlfriend of eight years, Jenna Morasca, were eliminated on The Amazing Race. "There was literally nothing to do where we were hanging out," he tells PEOPLE. "So I went jogging every day."
And when his doctors told him in September that his Hodgkin's lymphoma had returned, he had "no hesitation whatsoever that I would still run in the marathon," he says. "But a lot of other people did."
Zohn's new "smart chemotherapy" SGN-35, which only targets the cancerous cells, allowed him to continue his training. "If I was on the other type of chemo, I wouldn't be able to run," he says. "This drug came out while I was in remission. Everyone who is running has a cause and I'm living proof that it works."
In addition to his training, Zohn focused more on his diet, eliminating white flour and sugar, and eating more complex carbohydrates, fish and whole grains. "I'm a skinny guy so it's tough because I'm losing a lot of weight from running," says Zohn, who also supplements with Muscle Milk and Soy Joy bars. "I'm trying to eat as much as possible to keep on the weight."
Morasca will be cheering for Zohn throughout the course, alongside pal and former Bachelorette Trista Sutter, whose husband Ryan is also running in the race.
Zohn's fans also can track him online by his number, 45-910, as he makes his way through the city. His organization, Grassroot Soccer, will have a cheering section at 104 Street and Fifth Ave.
"I have a competitive spirit and I like to challenge and push myself," says Zohn, who finished the race in four hours and 16 minutes last year. "This time, I'm proud and I'm excited. Finishing for me is going to be a big deal. I'm going to walk, shake hands, give high-fives and kiss babies. I'm going to have the time of my life."
