"I was off chemo," he says. "I was running up to seven miles" in preparation for November's New York City Marathon. "I was happy, I was going out. I went up to Boston to see the family and was feeling great."
Then, on Aug. 26, his doctor called with post-chemo test results – and they were not good. "My cancer is back," Zohn, 35, tells PEOPLE. "I have never been so scared in my life, for my life."
"It was a complete punch in the face," says the Survivor: Africa winner, who had been making regular video diaries for PEOPLE.com. (Stay tuned for the latest chapter.) When the bad news hit, Zohn decided to wait until doctors started him on a new course of treatment before sharing the news with family, friends and now the rest of the world.
Family Reaction"My mom was obviously upset," Zohn says. "My brothers – everyone's upset. They can't believe it's what's happening. But on the flip side, everyone's positive and supportive."
He adds, "You have to think positive. And you have to find the strength, which I will. And you have to rely on other people, which I will."
The chemotherapy Zohn had endured since May left him hairless and plagued by nausea. But it did have some positive effect: The mango-sized tumor in his chest shrunk significantly. "The original mass is pretty well contained," Zohn says.
That's the good news. The bad news showed up on PET and CAT scans: "There was re-growth," Zohn explains. "Two little nodules in a different location … It's quite rare that not only is there re-growth, but that there's re-growth so quickly. I was obviously resistant to the first form of chemotherapy."
Now, doctors have ordered a stem cell transplant aimed, as he puts it, at "hitting the reset button" on his body.
New TreatmentThe new treatment – officially called risk-adapted high dose chemoradiotherapy and autologous stem cell transplantation for patients with relapsed and primary Hodgkin's lymphoma – will take place in three stages.
The once-shaggy-haired soccer player just emerged from the first part of stage one: He spent three days in a hospital last week, where he received a combination of chemotherapy drugs referred to as ICE. Since Zohn's immune system was in such a fragile state, his girlfriend, Survivor: The Amazon winner Jenna Morasca, slept in a chair at his bedside each night dressed in a hospital gown, protective mask and rubber gloves.
After three weeks of rest, he'll return to the hospital for a second in-patient ICE treatment that will last four days. Doctors will then harvest healthy stem cells from Zohn's body and freeze them for later use.
"In stage two I will get blasted twice a day for 14 days with a high dose of radiation," Zohn told friends via e-mail last week. "In the final and most difficult stage, I will be admitted to the hospital for 30 days (yes a whole f'ing month), to get my final chemotherapy session to start my stem cell transplant."
Remaining PositiveZohn says that both his red and white blood cell count will be brought down to zero during the month-long hospital stay – most likely in December – at which time his frozen, healthy stem cells will be reintroduced with the aim of replenishing his body entirely with non-cancerous cells.
"Then I'm cured," he said in his e-mail to friends, showing his usual air of hope and humor. "Easy as 1, 2, 3 … 4, 5, 6, 7, 8, 9 … 1000 … 1,000,000."
As he has since beginning his battle, Zohn is vowing to remain positive. "Whatever things are thrown at you, you've got to battle through with a smile on your face," he says, "and the important people in your life around you."