Joyce Ares just turned 74, and she felt fine when she agreed to provide a blood sample for the study. So she was surprised when a screening test came back positive for signs of cancer.

After repeated blood tests, PET scans and needle biopsies, she was diagnosed with Hodgkin lymphoma.

“I cried,” said the retired real estate agent. “Just shed a few tears and thought, ‘Okay, what do we do now?'”

The Camby, Ore., resident volunteered for a blood test billed as a new frontier in cancer screening for healthy people. It looks for cancer by examining the DNA fragments shed by tumor cells.

This blood test, known as a liquid biopsy, is already used in cancer patients to adjust their treatment plans and to check if tumors will come back.

Now, a company is promoting its blood test to people with no signs of cancer as a way to detect tumors in the pancreas, ovaries and other sites for which no screening is recommended.

Whether this cancer blood test, if added to routine care, could improve Americans’ health or help meet the White House’s goal of halving cancer mortality over the next 25 years is an open question.

As advances in DNA sequencing and data science make blood tests possible, California-based Grail and other companies are racing to commercialize them.

U.S. government researchers are planning a large experiment — potentially lasting seven years and involving 200,000 participants — to see if the blood test can deliver on the promise of detecting more cancers earlier and saving lives.

“They sound great, but we don’t have enough information,” said Dr. Lori Minasian of the National Cancer Institute, who was involved in planning the study. “We don’t have clear data that they reduce the risk of dying from cancer.”

Grail is far ahead of other companies, with 2,000 doctors willing to prescribe the $949 test. Most insurance plans do not cover fees. These tests are marketed without endorsement by a medical group or recommendation by U.S. health authorities. Such tests do not require review by the Food and Drug Administration.

“For a drug, the FDA requires that there is a high probability that the benefits not only outweigh the harms. This is not the case for devices such as blood tests,” said Dr. Barry Kramer of the Lisa Schwartz Foundation for Medical Truth.

Grail plans to seek FDA approval, but is pitching its test when it submits data to the FDA.

The history of cancer screening tells us to be cautious. In 2004, Japan stopped 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 the UK found that regular ovarian cancer screening had no effect on mortality.

Cases like this uncovered some surprises: Screening found some cancers that didn’t need a cure. reverse? Many dangerous cancers grow so fast that they evade screening and prove fatal.

Screening does more harm than good. Anxiety about false positives. unnecessary costs. Serious side effects of cancer treatment: PSA testing in men can lead to treatment complications, such as incontinence or impotence, even though some slow-growing prostate cancers never cause trouble.

The evidence is strongest for screening tests for breast, cervical and colon cancers. For some smokers, lung cancer screening is recommended.

Recommended tests—mammograms, PAP tests, colonoscopy—look for one cancer at a time. New blood test can look for multiple cancers at once. That’s an advantage, according to Grail executive Dr. Joshua Ofman.

“We screen for four or five cancers in this country, but (many) cancer deaths are from cancers that we simply don’t look for,” Ofman said.

Dr. Tomasz Beer of Oregon Health & Science University in Portland led the company-sponsored research, with Joyce Ares joining in 2020. After a painful winter of chemotherapy and radiation, doctors told her the treatment was a success.

Her case isn’t an outlier, “but it’s a hoped-for outcome that not everyone will have,” Beale said.

While other early-stage cancers were found in study participants, some had less clear-cut experiences. For some, scans resulting from a blood test never find cancer, which could mean a false positive result, or it could mean a mysterious cancer will develop later. For others, the cancer detected by the blood test turned out to be advanced and aggressive, Beer said. A seriously ill elderly participant refused treatment.

Grail has continued to update its test after learning from these studies, and is sponsoring a trial of 140,000 people with the UK’s National Health Service to see if the blood test can reduce the number of advanced cancers.

Kramer, the former director of the National Cancer Institute’s Division of Cancer Prevention, said that while Ares was lucky, there was no way to know if her test had added healthy years to her life or if it had not really changed.

“I sincerely hope Joyce will benefit from this test,” Cramer said of her experience. “But unfortunately, on Joyce’s personal level, we don’t know if that’s the case.”

Cancer treatment can have long-term side effects, he said, “and we don’t know how fast the tumor will grow.” Treatment for Hodgkin’s lymphoma is so effective that delaying treatment until she feels symptoms might achieve the same happy outcome.

Currently, health experts stress that the Holy Grail blood test is not a cancer diagnosis; a positive result triggers further scans and biopsies.

“This is an avenue of diagnostic testing that has never been tried before,” Cramer said. “Our ultimate goal is a test with a clear net benefit. If we’re not careful, we’ll stray from that path. “