"I was feeling like I needed an explanation."(ELISSA THORNER)It's a question many woman with breast cancer ask themselves: Why me? Why did I get this disease? The evidence remains inconclusive about what in your lifestyle contributes to breast cancer. And what if you're about 25 years younger than the average breast cancer patient?

Elissa Thorner, of Baltimore, was training for a triathlon when she got her diagnosis—at the age of 23. She had been eating organic food for years, never smoked, hardly drank, and was on her way to finishing an advanced degree in public health. When her mammogram came back with the dreaded news, at first she was simply incredulous.

"There was an immediate feeling of disbelief, that there must have been a mistake, and a level of shock that I shouldn't get breast cancer, especially when I had done everything right," Thorner recalls.

Fast on the heels of the disbelief was rage: "I went through unbelievable anger, feeling my body had failed me. I remember being out at a bar with a girlfriend—she was having a cosmo and a cigarette—and feeling how unfair it was. She sleeps with random men and lives a single bachelor life, and I've never done anything like that."

[ pagebreak ]Thorner couldn't help but wonder if the stress on her body from training for races or the hormones from the hamburgers and milk in her past had contributed to her tumor. "I'm a scientist by training, and I started reading a lot," she says. "I wanted genetic testing, I demanded brain scans, bone scans, an MRI. I was really feeling like I needed an explanation." But even after trips to four leading cancer centers around the country, she found no satisfying answers, nothing that could really explain why she was among the unlucky few.

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Then Thorner was diagnosed with a breast cancer recurrence on her 25th birthday. "The recurrence was more infuriating than the first diagnosis," she says. "I did everything [my doctors] told me to do and I got sick again." She suffered through a bilateral mastectomy and the discomfort of tissue expanders when she had reconstructive surgery in the summer of 2007.

But this time, she knew there wasn't going to be a good explanation for her cancer, so she took a new approach: reshuffling her own priorities and helping other young women with breast cancer through her work with Susan G. Komen for the Cure, among other organizations.

"I'm a very different person than I was before cancer," says Thorner. "When I was sick in treatment the first time, I had to slow down; I got radiation pneumonia and I wasn't responding well to treatment. Now I only work part-time, and I definitely learned that I can go to the gym and not do 20 miles—I can just walk. I was running to get to the end of the marathon, but now it's about the journey."