血液检测是癌症治疗的重大突破

One of the most exciting developments in cancer research in the past decade involves trials going on right now at four cancer treatment centers in the United States. The centers are using a highly sensitive, new blood test developed at Massachusetts General Hospital in Boston. The test may revolutionize the way cancer is treated.

As tumors grow, they release cancer cells into the blood stream. This new test promises to detect the smallest traces of cancer cells circulating in the blood.

Dr. Dennis Haber, one of the researchers, said, "For every one tumor cell in the blood, there are over a billion blood cells in circulation. So that's the big challenge in a test that can pull out one in a billion cells."

In the new test, a blood sample is run across a microchip that is treated with a special glue. Then, Dr. Mehmet Toner said, "All these cells go through the chip, but only cancer cells are recognized by the chip and they stick to the chip."

The healthy cells pass on. The hope is that by measuring the number and types of cancer cells in the blood, doctors can tell whether a patient's treatment is working.

Dr. Elmer Huerta is a past president of the American Cancer Society. "What I try to do if I give a treatment is to see if the tumor is shrinking and is disappearing in an X-ray, a CT scan, or an MRI," he said.

But it is sometimes months later before a biopsy or X-ray shows if the treatment is working.  And critical time is lost if the cancer continues to grow. With the new test, doctors will know immediately if the patient still has cancer. "That is the avenue that is opening before our eyes is that the follow-up of cancer patients will be much more guided and much more precise," said Dr. Pearson. "If we use this technology well, we will find the recurring cases earlier and we will treat them accordingly with new medications."

Greg Verttos, in the clinical trial in Boston, has advanced cancer. "This would really allow prompt response. And for me, that would really make all the difference in the world," he said.

Right now, the trials are limited to cancer patients. But the technology raises a question: could a blood test be developed for seemingly healthy patients?

Breast cancer specialist Dr. Susan Love says not now. "We all have cancer cells in our bodies that are not really causing any problem.  What we have to be careful of with this new technique, is over-treating the dormant cells which were never going to give us any problem in our attempt to get every cell we can see," she said.

The trials are expected to run for about five years.  In the meantime, Dr. Huerta says people have to be vigilant. "While we wait for this technology to flourish and to mature, we have to remember that cancer is silent and, although imperfect, the best things we have nowadays to detect early cancer are pap smears, mammograms, fecal occult blood, colonoscopies and prostate examinations. And of course, a clinical examination by a doctor," he said.

If the trials are successful, researchers hope to make the test widely available.