Father Dennis Billy, C.Ss.R., was patient number 3 in the new treatment at Memorial Sloan Kettering Cancer Center.
Researchers at Sloan Kettering detailed their success in the phase one trial in the journal Science Translational Medicine.
Father Billy says his first sign of being sick was in May 2010.
"Slight headaches, fever. I remember in the middle of May I was supposed to go to an event in New York, and I couldn't even bear the thought of driving," he recalls.
Ever since those first symptoms, Father Billy has kept a journal of his battle with leukemia.
It tells how he was close to remission twice, only to see the cancer come back - fast and hard.
"They did a bone marrow biopsy there, and they told me it had gone from 8 per cent to 70 per cent in 10 days. So I was pretty much up a creek," he says.
"Being a priest, a man of faith, I was preparing myself for the end," he says.
Only 30% of adults who relapse with A-L-L respond to last-ditch chemotherapy.
But his doctor at Sloane Kettering said there was one more specialist he wanted him to see.
It turned out to be Dr. Renier Brentjens, who was working on an experimental treatment using the body's own disease-fighting cells.
Normally, these T-cells won't attack leukemia
However, they were genetically modifed to attack, then re-introduced into Fr. Billy's body using a harmless virus.
It worked, wiping out Fr. Billy's cancer.
And it worked for 16 other patients like him -
He's been in remission more than 2 years - back teaching moral theology at St. Charles Borromeo Seminary.
For extra protection, he also got a bone marrow transplant from his younger brother Richard , a retired New York City firefighter who barely survived the World Trade Center disaster.
"He was in the North Tower, and barely got out alive," he notes.
Richard Billy was one of just 6 members of his engine company to get out.
Father Billy says he is back exercising, especially jogging, a lifelong interest.
Last summer, the brothers completed a 5K race together.
"We call ourselves the Bone Marrow Brothers," he says with a smile.
"I feel very fortunate, very blessed."
Locally, the University of Pennsylvania and Children's Hospital are having success with a similar technique.
But this is the largest clinical trial for adults with A-L-L, and so far, has the longest survival rates.