Sgt. Alan Castillo has never been to Iraq or Afghanistan, but is a veteran of another war, one he faces every day. Just days before deploying for his first combat tour, Castillo learned he would be fighting for his life here at home. "When I was down at the [Fort Benning, Ga.] combat readiness center preparing for my deployment, that's when I found out my cancer had come back," said Castillo, intelligence analyst, Fort Sam Houston, Texas Warrior Transition Unit."Not only had it come back, but it had come back pretty aggressively." In January of 2009, after his first diagnosis of colon cancer, Castillo underwent surgery to have the tumor removed. 30 days after his surgery, Castillo recalled being back to his old self, taking a physical fitness test and participating in unit combatives training. Three years later and battling a rare form of cancer which had spread to his lungs, liver and throughout his lymph nodes, Castillo fears he may have to hang up his combat boots for good. "I absolutely love the Army and everything it stands for. I was more upset with possibly being taken out the Army than I was with the fact that I had cancer," said Castillo. Castillo, who joined the Army in February of 2008, said it meant everything for him to honor his nation, but more so, to continue his brother's legacy. " My older brother served a few tours in Iraq and a few tours in Afghanistan and got hurt pretty badly and now he is a disabled vet," said Castillo. "I wanted to follow in his footsteps because I felt like it was a duty to my country. There are so many who can't [serve], but I was in that percentile that could." Castillo arrived to 3d U.S. Infantry Regiment (The Old Guard) shortly after completing his initial Army training and immediately felt privileged to serve in such a unique unit. "Between my colleagues in my field, I felt like I had a very different career than them," explained Castillo. "I had the honor to serve in a unit who lays our fallen comrades to rest." After being re-diagnosed with cancer, Castillo returned to The Old Guard until he was reassigned to the Fort Sam Houston, Texas Warrior Transition Unit while seeking treatment at the University of Texas MD Anderson Cancer Center. Although Castillo knew getting better was his number one priority, transitioning out of The Old Guard left him feeling devastated. "I loved my job," said Castillo. "I went from everything Army to not having the energy to go run five miles or put on my uniform. [I've gone] from a person who was use to always running around doing something to a person who just couldn't do anything." He added the chemotherapy he receives hasn't made the move any easier. "If you've talked to anyone who has done chemotherapy before, they will tell you it's like a roller coaster ride. You feel ok the day of but the next day you start to get run down and the next day after that you get more run down until you just hit the bottom where you have no energy," said Castillo. After learning that his initial line of chemo stopped working, Castillo remained optimistic about his treatment and continued to push forward for a cure. "The studies they do are based on people who are 50 to 70 years old. I'm half the age of anyone else who happens to have colon cancer so that makes me different," said Castillo, who is 27 years old. "I'm on to experimental drug trials now." Every three weeks, Castillo is readmitted to the hospital where he receives treatment through chemo medicine that is pumped directly into his liver. Although the success of the procedure is uncertain, Castillo's fighting spirit is greatly influenced by the overwhelming support of his wife. "My wife is a saint," Castillo exclaimed. "It's hard being the person receiving the treatment but it's even harder sometimes being the caregiver. She's the one who has to see me going through everything. She's the one that sees me suffer. She's wonderful and the best thing that has ever happened to me." However, Castillo's wife is only half of the driving force behind his will to live. "If they hadn't caught it, they gave me six to eight months to live. With treatment it's hard to gauge." said Castillo. "I was feeling really bad and I thought my time was coming, but I have a daughter who is three and I want to see her go to kindergarten. I'm going to continue to fight this. In my mind I'm not letting this beat me."