In preliminary research that's been dubbed "remarkable," "dramatic" and "sensational," doctors made the most common type of leukemia disappear in two patients, and reduced cancer cells by 70 percent in a third.
Researchers at the University of Pennsylvania transformed patients' own white blood cells into "serial killers" capable of annihilating cancer cells within the body. The two patients who experienced full recovery are still in remission more than a year later.
Right now, the only way to cure leukemia is through a bone marrow transplant, which carries several risks.
"[The serial killers] can kill one tumor cell and then go and kill another, and we found in all three of our patients that the T-cells killed at least a thousand tumor cells, and that's the first time that has ever been shown anywhere near that kind of efficiency," said Dr. Carl June, the lead author of the study, in a video released with the research.
"Previous attempts to engage the immune system in destroying cancer cells have often relied on 'vaccination' with tumor cells or tumor proteins," Dr. Douglas Faller, director of Boston University School of Medicine Cancer Center, wrote in an email to ABCNews.com.
But in this case, researchers genetically altered and reprogrammed the killer cells of the immune system to recognize the leukemia tumor cells, Faller noted.
And for the million dollar question: What does this mean for the future of cancer treatment?
"This is an evolving area of treatment that is pretty sophisticated," said Dr. Steven Rosenberg, chief of the surgery branch at the National Cancer Institute. "Someone needs a fair amount of expertise in immunology and molecular biology, and there are very few groups that can do this around the world."
In 2006, Rosenberg published the first study in which T-cell receptors were used for gene therapy, combined with chemotherapy, in 17 people who had advanced melanoma. Two patients from the trial remained disease-free several years after the study.
Since then, a tumor-specific approach to treatment has been used in clinical trials of patients who had breast, prostate, sarcoma and colon cancer.
"This study is probably the most clear-cut, well-studied and best-described of cases," said Dr. Renier J Brentjens, a medical oncologist at Memorial Sloan-Kettering Cancer Center, who specializes in treating acute and chronic leukemia through immunology. "It's very clear here that T-cells are responsible for this effect, and the effect is sustained."
While the excitement among oncologists and the general public is apparent, experts cautioned that it was too early to tell whether this will become a mainstream cancer treatment. The final verdict is likely years away, experts said.
"[This] probably indicates that this kind of treatment is possible but hugely resource-intensive, and the longer term toxicities and efficacy are not at all clear," said Dr. Bruce Chabner, clinical director at Massachusetts General Hospital Cancer Center. "It could be historic, but it will take several more years and many more cases before we know."
"These are expensive trials, and it's hard to get funding," said Brentjens. "It might be a little easier now that these papers are published, but you still need a highly expert staff of well-trained specialists. It's a pretty large operation."
Even with the proper monetary resources, only a handful of facilities across the country are capable of making these cells.
Despite the financial and staffing hurdles, Brentjens remains optimistic.
It gets me up every morning knowing that this is the future," said Brentjens. "This is very exciting, and I hope and pray that immunotherapy will one day replace the more toxic chemotherapy for treatment in cancer patients."