美国批准新的癌症治疗方法

Doctors are calling it a milestone. The U.S. Food and Drug Administration has approved a first-of-a-kind prostate cancer treatment. It is not a cure, but it can extend the lives of those fighting the disease.

The idea is simple: use the body's immune system to fight cancer. Doctors have been developing these immunotherapies for decades. Now they're saying there's a vaccine for prostate cancer.

Its name is Provenge.

In clinical trials, Provenge has been used on men like Tom Keil, men who look healthy, generally feel good, but have advanced prostate cancer, meaning it has spread to the bone or lymph nodes.

"Right now I'm in good shape. There's no difficult problem with the cancer that I know of," he said.

The clinical trials show Provenge increases a patient's life span by an average of four months. But some patients have lived much longer.

Dr. Charles Drake works on treatments for prostate cancer at Johns Hopkins University. He tells VOA this is an important breakthrough. "Although four months doesn't sound like a lot, especially from the patient's point of view, I totally understand what you're saying, but in the world of cancer, a four-month survival with good quality of life, that's pretty significant, actually,' he said.

Provenge is not a traditional vaccine; it does not prevent disease.

It takes some of the patient's white blood cells which are then treated so they will attack the cancer.

Then the cells are re-injected into the patient. "It's been relatively easy. The hardest part is sitting down for two and a half to three hours while the white blood cells are taken out and separated. I'm a restless person," he said.

Keil's doctor, Nancy Dawson, told VOA she likes it for other reasons. "It's a very well tolerated therapy. Very few side effects," she said.

And unlike chemotherapy or radiation, the treatment is quick. "It's given as three infusions, each one two weeks apart. Basically, at the end of four weeks, you've finished the therapy," she said.

But there are things Provenge does not do. "It doesn't make the marker of (prostate) cancer, which is the PSA, it doesn't usually make the PSA decrease. It doesn't make their cancer regress," she said.

Some doctors would like to see Provenge used earlier in the disease, after initial surgery or radiation, to destroy any remaining cancer cells and extend life even more. "I think we'll start to have the kind of clinical benefits that you alluded to, you know, more than four months. We want long-term survival, frankly. Maybe a cure," said Dr. Drake.

Dr. Drake says this type of treatment will also be used for other types of cancer.

It will take a while for Provenge to become widely available. But prostate cancer grows relatively slowly so many men may be able to benefit from this treatment.