Meanwhile, three months in to chemotherapy and radiation, Srsich got a visit in the hospital from the Colorado Make-A-Wish Foundation, which helps about 250 children a year realize a dream come true.
"At first I was a little concerned -- I thought [of it] as for terminally sick children who had no chance and were getting one last wish," he said. "I thought there was something the doctors were not telling me."
But after chatting, he told them his top wish was to go to Rome to see the Pope, not just to go to Disneyworld or meet Justin Bieber.
"I would have been perfectly fine if I just got a tour of the Vatican," he said.
Srsich met the criteria: "a child with a life-threatening medical condition, progressive and malignant at the time of the referral [by a physician]," according to the national Make a Wish Foundation.
"There have been wishes more complicated, wishes that cost more money," said Jennifer Mace-Walton, director of wish giving. "His was one of the most unique."
The $14,000 trip, which included airfare, hotel, food and spending, was arranged with the help of the Italian chapter of the organization.
"After meeting Peter, there was no doubt in my mind it was his true wish and it was going to play an important role in what he wants to do career-wise," said his gift coordinator LuAnn Griffin.
The immediate family was thrilled to be able to hear the pope speak in five languages before a large audience. Afterward, they were called to stand before him in a line of dignitaries, including five-star generals from the Italian army.
"At that point, I realized I would get to have a conversation with him," Srsich said. "Everyone was bringing gifts and I started freaking out.
"I am standing like the little drummer boy with nothing to offer," he said. "There were golden crowns and a 4-foot tall magnificent painting of Mary and I am sitting there with a 70-cent rubber wristband."
His father handed the teen his wristband, the one that said, "Pray for Peter."
At 6-foot-6, Srsich towered over the short Pope and after a two-minute introduction, told him about his cancer, asking for a blessing.
"He looked at me and said, 'Oh, you speak English?' and put his hand on my chest right where the tumor had been, even though I had not mentioned it to him," he said. "The blessing is usually on the head."
Srsich said he was "in awe of how humble he was."
Today, Srisich feels "wonderful" and is back playing college lacrosse and is soon testing for his master in Taekwondo. And, despite the medical set-back, he is still on track to be an ordained priest in about eight years time.
"Every time people see cancer and the pope, they assume it's a miraculous healing," he said. "Chemo helped me fight the cancer. Make-A-Wish helped me fight the chemo. Knowing the pope was in my future helped me get through that, and in a small, non-miraculous way, helped cure my cancer."