Gilbert was diagnosed when he was 14 years old, and after he went into remission the first time around, he was told he would have to do routine MRIs to help screen for any recurrence.
“In October, it was clean as a bell, and we come in February, and there’s a tumor about the size of a dime,” he said.
Gilbert says he had no signs or symptoms.
“I think it was more of a shock to me than the first time because the first time I didn’t really know how to take it, and I was just like, 'OK, let's beat it just like any other disease,” he said.
Now he’s back in and out of hospitals battling stage 4 brain cancer.
“They’ve been giving me more aggressive drugs than the first time,” he said.
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Gilbert told ActionNewsJax that he had two goals after being diagnosed: to go to prom and to graduate. On Saturday, he celebrated the latter milestone with his family.
“This represents a lot of accomplishment,” said his mother, Kimberly Herbert, as she held up his diploma.
She said when her son walked across the stage, she cried.
“I did, I cried. It was just a proud moment. Very proud,” Herbert said.
Gilbert also got to go to prom, too.
Herbert and Gilbert even created a Facebook page, "#TeamTrevor," with more than 1,600 followers and support pouring in from around the world.
They post updates and talk about Trevor’s journey.
Two weeks ago, he pushed himself to go to his senior band banquet.
After graduating, Gilbert said he would like to either go to University of North Florida or University of Florida to become a nurse and study oncology after going through what he’s experienced.
The teen told ActionNewsJax that he hopes his story will inspire others going through the same thing to push themselves a little more each day.
“You don’t want to do too much but you need to put forth a little effort because you’ll thank yourself for it later down the line,” Gilbert said.
Gilbert was put in a clinical trial back in March and will now finish two more cycles of chemotherapy in June.
In July, he will undergo a stem cell transplant.