Doctors have treated only three leukemia patients, but the sensational results from a single shot could be one of the most significant advances in cancer research in decades. And it almost never happened.

Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

In the research published Wednesday, doctors at the University of Pennsylvania say the treatment made the most common type of leukemia completely disappear in two of the patients and reduced it by 70 percent in the third. In each of the patients as much as five pounds of cancerous tissue completely melted away in a few weeks, and a year later it is still gone.

The results of the preliminary test “exceeded our wildest expectations,” says immunologist Dr. Carl June a member of the Abramson Cancer Center's research team.

Dr. Edgar Engleman, a cancer immunologist at Stanford University School of Medicine who was not involved in the research calls the results “remarkable ... great stuff.”

The Penn scientists targeted chroniclymphocytic leukemia (CLL), the most common type of the blood disease. It strikes some 15,000 people in the United States, mostly adults, and kills 4,300 every year. Chemotherapy and radiation can hold this form of leukemia at bay for years, but until now the only cure has been a bone marrow transplant. A bone marrow transplant requires a suitable match, works only about half the time, and often brings on severe, life-threatening side effects such as pain and infection.

In the Penn experiment, the researchers removed certain types of white blood cells that the body uses to fight disease from the patients. Using a modified, harmless version of HIV, the virus that causes AIDS, they inserted a series of genes into the white blood cells. These were designed to make to cells target and kill the cancer cells. After growing a large batch of the genetically engineered white blood cells, the doctors injected them back into the patients.

In similar past experimental treatments for several types of cancer the re-injected white cells killed a few cancer cells and then died out. But the Penn researchers inserted a gene that made the white blood cells multiply by a thousand fold inside the body. The result, as researcher June put it, is that the white blood cells became “serial killers” relentlessly tracking down and killing the cancer cells in the blood, bone marrow and lymph tissue.

As the white cells killed the cancer cells, the patients experienced the fevers and aches and pains that one would expect when the body is fighting off an infection, but beyond that the side effects have been minimal.

Doctors had told Bill Ludwig, one of the research volunteers, that he would die from his leukemia within weeks. Then he got the experimental treatment a year ago.

With tears welling up, he told NBC, "I'm more closer to the people I love and I appreciate them more... I'm getting emotional... the grass is greener and flowers smell wonderful."

The other two patients have chosen to remain anonymous but one who happens to be a scientist himself wrote, “I am still trying to grasp the enormity of what I am a part of -- and of what the results will mean to countless others with CLL or other forms of cancer. When I was a young scientist, like many I’m sure, I dreamed that I might make a discovery that would make a difference to mankind – I never imagined I would be part of the experiment.”

So why has this remarkable treatment been tried so far on only three patients?

Both the National Cancer Institute and several pharmaceutical companies declined to pay for the research. Neither applicants nor funders discuss the reasons an application is turned down. But good guesses are the general shortage of funds and the concept tried in this experiment was too novel and, thus, too risky for consideration.

The researchers did manage to get a grant from the Alliance for Cancer Gene Therapy, a charity founded by Barbara and Edward Netter after their daughter-in-law died of cancer. The money was enough to finance the trials on the first three patients.

With results for the three patients published Wednesday simultaneously in the New England Journal of Medicine and Science Translational Medicine, money for further studies -- not just in this one type of leukemia, but in other cancers -- will likely pour in from both the government and drug companies.

It is important to emphasize that there still have been only three patients. Over the past century, many attempts to harness the body’s immune system to fight cancer have shown initial success and subsequent failure. So much research remains to be done to prove just how good this treatment is. But it should begin soon, with great vigor.

Video: New leukemia treatment shows promise

Closed captioning of: New leukemia treatment shows promise

>>>as we have been telling you here tonight, there is some good news to report in the fight against cancer, an experimental treatment for leukemia is having extraordinary results beyond any expectations. it's small so far but the results are big enough to get out to the world and tonight as our chief science correspondent
robert bazell
reports, if it hadn't been for one woman who suffered a loss, this very promising research might not have happened.

>> reporter: bill ludwig
says doctors tell him without the experiment treatment he would have had only weeks to live.

>>i'm in full health, no cancer in my system.

>> reporter: he has gotten the experiment treatment. the results are so spectacular that many believe it could mark the beginning of a major advance in cancer treatment.

>>each of those patients, a one or two of tumor was eradicated.

>> reporter: it removes the
blood cells
and -- attach to and kill
cancer cells
and return them to the patients in one infusion.

>>how good were those results compared to your expectations?

>>the results exceeded our expectations quite a bit. our entire team is really excited. and as well, the patients are excited.

>> reporter: why only three patients? the research concept was so new that neither the
national cancer institute
would fund it. she and her husband started a charity to fund new ideas after their daughter-in-law kim died of
breast cancer
.

>>we wanted to do something more, hoped to do something more.

>>so here it's just full of leukemia and now it's gone. money from the
drug companies
is pouring in, not just for further tests on leukemia patients but to try on patients with other cancers. for now, three lives have been saved.
robert bazell
, nbc news, philadelphia.