VOA健康报道2022--血液检测能拯救癌症患者的生命吗?（在线收听）

Can Cancer Blood Tests Help Save Lives?

Joyce Ares was feeling fine when she agreed to get a blood test for research. So, she was surprised when the test came back with signs of cancer.

After a repeat blood test and two more tests for cancer, she was found to have Hodgkin lymphoma.

"I cried," the 74-year-old retiree said. "Just a couple of tears and thought, ‘OK, now what do we do?'"

Ares had volunteered to take a blood test that is being viewed as a new way to check for cancer among healthy people. It looks for cancer by checking for DNA parts broken from shed cancerous cells.

Such blood tests, called liquid biopsies, are already used in patients with cancer to establish treatment and check to see if cancerous growths come back.

Several drug companies are pushing for the blood test as part of regular health screening to find cancerous growths, or tumors, in certain parts of the body.

Grail, a California-based company, is far ahead of others with 2,000 doctors willing to prescribe the $949 test. Most insurance plans do not cover the cost.

The Food and Drug Administration demands an extensive study of a drug or vaccine before approval. A review by the agency is not required for this kind of blood test. But Grail plans to seek approval from the FDA while it is marketing the tests.

Experts are not sure whether the tests could improve Americans' health or help cut the cancer death rate. U.S. government researchers, meanwhile, are planning a large trial with 200,000 volunteers over seven years to study the blood tests.

"They sound wonderful, but we don't have enough information," said Dr. Lori Minasian of the National Cancer Institute. She is involved in planning the research. "We don't have definitive data that shows that they will reduce the risk of dying from cancer."

Cancer screening

The history of cancer screening has served as a warning.

In 2004, Japan halted mass screening of infants for childhood cancer after studies found it did not save lives. Last year, a 16-year study of 200,000 women in Britain found regular screening for ovarian cancer did not make any difference in deaths.

Cases like these have uncovered some surprises: Screening finds some cancers that do not need treatment. On the other side, many tumors spread so fast that they prove to be deadly anyway.

Cancer screening, at times, can do more harm than good. It leads to worry over false positives, unnecessary costs, and serious side effects from cancer care.

Dr. Joshua Ofman is an official with Grail. He said current screening tests only look for one kind of cancer at a time, including breast, cervix, colon or lung. The new blood tests look for many cancers at once.

"We screen for four or five cancers in this country, but (many) cancer deaths are coming from cancers that we're not looking for at all," Ofman said.

Dr. Tomasz Beer of Oregon Health & Science University in Portland led the Grail study that Joyce Ares joined in 2020. After chemotherapy and radiation, doctors told her the treatment was a success.

Beer said Ares' case is a "hoped-for ideal outcome." He added, "not everyone is going to have that." For some, Beer said the blood tests could bring false positives. For others, the tests found cancer that turned out to be advanced and aggressive.

Grail continues to update its test as it learns from these studies. The company is also working with Britain's National Health Service on a study of 140,000 people. They want to see if the blood test can reduce the number of advanced cancers.

Although Ares feels lucky, it is impossible to know whether her test added healthy years to her life or made no real difference, said Kramer, former director of the National Cancer Institute's Division of Cancer Prevention.

"I sincerely hope that Joyce benefited from having this test," Kramer said when told of her experience. "But unfortunately, we can't know, at the individual Joyce level, whether that's the case."

Cancer treatments can have long-term side effects, he said, "and we don't know how fast the tumor would have grown." Treatment for Hodgkin lymphoma is very effective. It is possible that Joyce would have had the same good results if she had sought treatment only after she showed symptoms.

For now, health experts say the Grail blood test is not a cancer diagnosis. "This is a path in diagnostic testing that has never been tried before," Kramer said. "Our ultimate destination is a test that has a clear net benefit. If we don't do it carefully, we'll go way off the path."

Words in this Story

shed – v. to lose naturally

ovarian - adj. of or related to ovary (an organ in woman's body that produce eggs and female hormones)

sincerely – adv. genuinely or truly

benefit – v. to be helped

diagnosis – n. the act of identifying a disease or illness

ultimate – adj. happening at the end