By Stephanie Emma Pfeffer
Updated December 07, 2015 09:55 AM
Credit: Courtesy Jenny Shapiro

Today Alexis Shapiro begins treatment for the benign brain tumor that was recently discovered to have grown back.

The 13-year-old girl from Cibolo, Texas, who has struggled with hypothalamic obesity learned in October that her craniopharyngioma had redeveloped.

“Alexis was so scared,” her mom Jenny Shapiro tells PEOPLE exclusively. “She did not want another surgery.”

First diagnosed with the benign tumor in 2011, Alexis underwent an operation to remove it and emerged with a damaged hypothalamus, the part of the brain that controls when a person feels hungry or full. Within months she developed hypothalamic obesity, a rare, irreversible condition that caused her to gain weight uncontrollably. She put on 150 lbs. in two-and-a-half years, weighing 203 lbs. by the time she was 12.

Meet Alexis Shapiro, a 12-year-old Suffering from Uncontrollable Weight Gain

Despite extreme attempts to lower her weight through diet and exercise, nothing worked – and her parents were afraid for her life. A sleeve gastrectomy in March 2014 improved Alexis’s health dramatically and she lost 60 lbs. She had a gastric bypass in August 2015 to continue her progress.

Alexis Shapiro Is Nearly 60 lbs. Lighter Following Gastric Sleeve Surgery

The family thought they were out of the woods until a routine MRI earlier this year showed that the tumor was back. After consulting with doctors and reviewing their options – including surgical removal and chemotherapy – the Shapiros applied to be part of a proton radiation study at St. Jude Children’s Research Hospital.

Compared to traditional chemotherapy, proton therapy “is more precise and may be used to deliver a potentially higher dose of radiation to the tumor with fewer side effects,” according to St. Jude’s website.

Alexis spent two weeks in Memphis at St. Jude’s main campus undergoing tests, MRIs and PET scans before heading to an affiliated hospital in Jacksonville, Florida, where the proton therapy machine is located.

“She made a mask that keeps her head in the exact same place every day,” says Jenny. “We need to stay for 30 treatments. She should be done in the middle of January.”

Unfortunately for Alexis, that means being separated from her family in Texas – dad Ian and siblings Kaylee, 11, and Ethan, 9 – for her Dec. 11 birthday, and possibly Christmas as well.

But maybe not: “A couple of wonderful people in our community put together a fundraiser so we can all be together for the holiday,” says Jenny. “An organization called Compassion Partners will give our family 3-day passes to Disney World. We just need to get them out here!”

Three months after Alexis completes treatment, she will return to St. Jude for evaluation – although Jenny says it could take up to two years before its full effects are realized.

But that is hope enough for the Shapiros. “If it works, there is an 80 percent chance of it not coming back,” says Jenny, who keeps supporters updated through a “Hope and love for Alexis” Facebook page.

“And Alexis has been such a trooper,” she says. “So brave!”