Can cancer blood tests live up to promise of saving lives?


              Vials of blood from a participant in a clinical study of the effectiveness of a new liquid biopsy technology are packaged for shipment at Oregon Health & Science University in Portland, Ore., on March 14, 2022. The clinical trial will follow hundreds of participants for three years to see if signals of any cancers that participants later develop were present in their blood. (AP Photo/Gillian Flaccus)
            
              Jacob Marquez, a clinical research coordinator at Oregon Health & Science University's Knight Cancer Institute in Portland, Ore., draws blood from clinical study participant David Parker on March 14, 2022. Parker is one of hundreds of people participating in a trial for a new liquid biopsy technology that could detect early signs of cancer in a person's blood. (AP Photo/Gillian Flaccus)
            
              Jacob Marquez, a clinical research coordinator at Oregon Health & Science University's Knight Cancer Institute in Portland, Ore., draws blood from a clinical study participant on March 14, 2022. Parker is one of hundreds of people participating in a trial for a new liquid biopsy technology that could detect early signs of cancer in a person's blood. (AP Photo/Gillian Flaccus)
            
              Joyce Ares checks on daffodils in her back garden on Friday, March 18, 2022, in Canby, Ore. She had volunteered to take a blood test that is being billed as a new frontier in cancer screening for healthy people. It looks for cancer by checking for DNA fragments shed by tumor cells. (AP Photo/Nathan Howard)
            
              Joyce Ares stands for a portrait in front of her home on Friday, March 18, 2022, in Canby, Ore. She had volunteered to take a blood test that is being billed as a new frontier in cancer screening for healthy people. It looks for cancer by checking for DNA fragments shed by tumor cells. (AP Photo/Nathan Howard)
            
              Joyce Ares plants a peony bud in her garden on Friday, March 18, 2022, in Canby, Ore. She had volunteered to take a blood test that is being billed as a new frontier in cancer screening for healthy people. It looks for cancer by checking for DNA fragments shed by tumor cells. (AP Photo/Nathan Howard)
            
              Joyce Ares plays with her poodles Gracie, left, and Oliver in the dinning room of her home on Friday, March 18, 2022, in Canby, Ore. She had volunteered to take a blood test that is being billed as a new frontier in cancer screening for healthy people. It looks for cancer by checking for DNA fragments shed by tumor cells. (AP Photo/Nathan Howard)
            
              Joyce Ares sits for a portrait in the dinning room of her home on Friday, March 18, 2022, in Canby, Ore. Although Ares feels lucky, it’s impossible to know whether her cancer blood test added healthy years to her life or made no real difference, said Dr. Barry 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. 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 so effective that delaying therapy until she felt symptoms might have achieved the same happy outcome. (AP Photo/Nathan Howard)
            
              Joyce Ares grooms her poodle Gracie in the garage on Friday, March 18, 2022, in Canby, Ore. She had volunteered to take a blood test that is being billed as a new frontier in cancer screening for healthy people. It looks for cancer by checking for DNA fragments shed by tumor cells. (AP Photo/Nathan Howard)
            
              Joyce Ares and her poodle Oliver water a recently-planted peony in her back garden on Friday, March 18, 2022, in Canby, Ore. She had volunteered to take a blood test that is being billed as a new frontier in cancer screening for healthy people. It looks for cancer by checking for DNA fragments shed by tumor cells. (AP Photo/Nathan Howard)
            
              Joyce Ares sits for a portrait in the dinning room of her home on Friday, March 18, 2022, in Canby, Ore. When she turned 74, Ares was feeling fine when she agreed to give a blood sample for research. So she was surprised when the screening test came back positive for signs of cancer. After a repeat blood test, a PET scan and a needle biopsy, she was diagnosed with Hodgkin lymphoma. (AP Photo/Nathan Howard)
Can cancer blood tests live up to promise of saving lives?