After three months of chemotherapy to treat a rare form of Hodgkin's disease, 'Survivor: Africa' winner Ethan Zohn was feeling pretty good. He was active, preparing for a marathon and "feeling great." But then came a call from his doctor on Aug 26, throwing cold water on his success.

"My cancer is back," he tells PEOPLE, in discussing post-chemo tests that showed re-growth of tumors in his chest. "I have never been so scared in my life, for my life." (Pictured, Zohn, left, poses with 'Pitchman' star Anthony Sullivan in August.)