Here’s a bit of good news! We now have a blood test for the early detection of 50 types of cancer. Here’s a bit of bad news; it costs $949 and isn’t covered by insurance! Oh my gosh! $949 and not covered by insurance, especially Medicare?
This test is called the Galleri Multi-cancer Early Detection (MCED) test. It was profiled in the most recent issue of American Family Physician, the scientific journal of the American Academy of Family Physicians. Until I read the article, I had not heard of this test, but it sounds very promising for the early detection of multiple cancers. When cancer is diagnosed early, there is a much greater chance of success in treatment.
The Galleri test is done from a routine sample of blood, but the mechanics of the test are rather complex and involve science beyond my knowledge. A simple explanation is when normal or cancer cells die, they release a form of DNA into the blood stream. This DNA is called circulating cell-free DNA (cfDNA), and it undergoes a chemical reaction the Galleri test detects. This reaction then identifies in the blood, indicators of as many as 50 types of cancer. The type and location of the cancer is not determined by the test, but “When a cancer signal is detected, the likelihood that the individual has cancer remains elevated and may warrant further evaluation……” So if you have a positive Galleri test, your physician will need to evaluate you to find the location and type of the cancer present.
The Galleri test is not to be used as a screening test, although it sounds like it is; and it is not intended to replace definitive screening procedures like colonoscopy, mammography, PSA testing, etc. The accuracy and reliability of the test increases as the stage of cancer increases. Cancers are staged I-IV depending on the advancement and growth of the disease. The Galleri test detects Stage I cancers 16.8% of the time, stage II 40.4% of the time, stage III 77%, and stage IV 90.1% of the time. If the test is positive, 99.5% of the time there is cancer in the individual.
The test is particularly sensitive for finding cancers of the rectum (81.3% likelihood), colon (82%), esophagus (85%), head and neck (85.7%), liver/bile duct (93.5%), ovary (83.1%), and pancreas (83.7%), but very poorly sensitive for cancers of the bladder (34.8%) and lymphomas (56.3%). A positive test means a cancer is present, but the physician still must begin a diagnostic work up to determine the site of the primary lesion.
It should be remembered the Galleri test is not a biopsy nor is it confirmation of cancer. It merely indicates that one of possibly 50 types of cancer is present in this patient. Once the site of origin is known, a biopsy is still necessary to confirm the diagnosis. In some ways, it is similar to a PET (Positron Emission Technology) scan which is done after cancer is diagnosed. It confirms the presence of cancer and determines its extent. Both PET and Galleri tests determine there is cancer, but neither can specify the cell type.
According to the author of the reference in Am Fam Phys, the widespread use of this test will require “additional long-term…population-based studies to further determine accuracy, clinical utility, and improved patient-oriented outcomes.” Until then, we can be optimistic that the Galleri test, and improvements of it, bode well for the future. Detecting cancer early is the best chance patients have of beating it, and the Galleri test sounds like it’s a step in that direction.
References: Neal RD, et al. Cell-free DNA-Based Multi-Cancer Early Detection Test in an Asymptomatic Screening Population: Design of a Pragmatic, Retrospective Randomized Controlled Trial. Cancers 2022;14:4818.
Diagnostic Tests: Galleri Test for the Detection of Cancer. Pyzocha NJ. Am Fam Phys. October 2022;106(4):459-460.
https.://www.am coming.com/view/novel-blood-based-early-cancer-detection-diagnostics-in-development.
Hackshaw A, et al. Estimating the population health impact of a multi-cancer early detection genomic blood test to complement existing screening in the US and UK. Br J Canc 2021 Feb;125:1432-1442.
