CancerSEEK: A new blood test that detects eight common cancers
The identification of eight common cancers ― ovary, liver, esophagus, pancreas, stomach, colorectal, lung, and breast cancer ― by a revolutionary new blood test is making headlines in the field of oncology.
Pioneering research by the Johns Hopkins Kimmel Cancer Center in Baltimore, Maryland measured circulating tumor DNA (ctDNA) from 16 genes as well as eight protein biomarkers, and then used machine-based learning to analyze the data generated. This means that the use of a combination of selected biomarkers has the potential to change screening and the early detection for the eight common cancers. This test could hold the key by which treatment for these cancers could be by surgery alone, considerably improving outcomes by avoiding systemic effects of other therapies.
Although still early days to be employed in the general population, the blood test uses a novel approach by identifying both mutations and proteins responsible for these cancers.
Segments of 16 genes determine mutations in ctDNA obtained from the blood sample along with an analysis of the levels of eight protein biomarkers namely cancer antigen 125, carcinoembryonic antigen (CEA), cancer antigen 19-9, prolactin, hepatocyte growth factor, osteopontin, myeloperoxidase, and tissue inhibitor of metalloproteinases 1. The mutational panel was deliberately kept small to minimize false positive results as well as to keep such tests affordable
The seminal study included 1005 patients with stage I to III cancers of the ovary, liver, esophagus, pancreas, stomach, colorectum, lung, or breast who had not yet undergone surgery. The most common stage at presentation was stage II (49%); 20% of patients had stage I disease; and 31% of patients had stage III disease. Controls included 812 healthy individuals who had no history of cancer.
The results indicated a median sensitivity of CancerSEEK, it was 73% for stage II cancers, 78% for stage III cancers, and a low 43% for stage I cancers. For stage I cancers, the highest sensitivity was for liver cancer (100%), and the lowest was for esophageal cancer (20%).
The median overall sensitivity — the ability to find cancer — was 70% for the eight common cancers ─ sensitivities ranged from 98% for ovarian cancer to a low of 33% for breast cancer. The sensitivities ranged from 69% to 98% for ovary, liver, stomach, pancreas, and esophagus cancers. The specificity of CancerSEEK was >99%.
The researchers also used an algorithm to determine the tissue of origin in patients with a positive CancerSEEK test. The accuracy was highest for colorectal cancer (84%) and lowest for lung cancer (39%). False-negative rates ranged from 2% in ovarian cancer to 67% in breast cancer. Mutations detected in blood samples almost always were identical to mutations in the primary tumor. The test accurately identified the cancerous organ in 63% of cases. Of note, 812 healthy controls underwent testing: the false-positive rate was 0.9%.
The study did have some limitations in that 80% of the cancers evaluated were stage 2 or stage 3 cancers (fairly advanced).
Demonstrating that a test can detect advanced cancers does not mean that the test will be useful in detecting early stage symptomatic cancers, much less pre-symptomatic cancers.
The sensitivity for the stage 1 cancers in the study was only 40%. Larger studies are needed to validate and reproduce these results, but this early liquid biopsy method seems an early encouraging step.
An early stage or a pre cancerous stage at diagnosis may throw some light on how to prevent cancers or modify the outcomes in patients by an early intervention.