It’s not often I find myself excitedly discussing cancer screening with anyone, let alone with my father-in-law during a family dinner. And yet, a Wall Street Journal article was thrust my way discussing a multi-cancer detection test that was, perhaps, more pleasant to conduct than something like a colonoscopy (1). This Wall Street Journal article specifically discusses the Galleri Test (2), a test that requires only a blood sample to detect molecular indicators of 50 different types of cancer.
We are all familiar with the single-cancer screenings available; colonoscopies to detect colon cancers, mammograms to detect breast cancer, pap tests to detect cervical cancers, etc. These single-cancer screenings occur at regular intervals over the course of a patient’s life, and may change in frequency depending on what is found, the patient’s genetic predisposition, or the change in clinical status. Ultimately, single-cancer screenings are based on algorithms from clinical trials and decades of patient data regarding disease detection and progression.
What is not yet available is an algorithm for multi-cancer detection tests, as multi-center clinical trials and broad-based longitudinal studies have not yet been conducted, and thus the lack of support from national organizations like the United States Preventative Task Force or the American Academy of Family Physicians (3). Essentially, the argument is that there has not been enough patient data to determine the true accuracy of the test in detecting a cancer or what should be conducted for subsequent testing.
The Galleri test has an excellent negative predictive value; 98.5%, meaning it is excellent at predicting that someone does not have cancer. This is comparable to a screening test that is now a standard option in colon cancer screening; the Cologaurd Test (4). But, what happens when a cancer is detected via the Galleri test? This is where we are lacking data and guidelines to help determine the course of action. There is a risk of false positive exams with every screening exam, and Galleri test needs to undergo more clinical trials to improve the positive predictive value. If a positive result is determined via the Galleri test with patterns consistent with ovarian cancer in an asymptomatic patient, how do we proceed? Ordering a diagnostic pelvic CT typically requires a symptom (therefore insurance may not pay for it), and if that diagnostic pelvic CT shows no abnormalities, what should be done then? We may find that the Galleri test is identifying these issues far earlier than traditional methods can; a thus, a positive test that is difficult to corroborate still provides valuable information to both the patient and care team, pinpointing a potential concern at an early stage.
Ultimately, we are all excited about serology tests like the Galleri to detect cancer at earlier stages than single-cancer screening exams (colonoscopies, mammograms, Paps, etc), but we have more to learn. The Galleri test does give us the ability to detect cancers earlier than other screening exams; and thus, receive treatment or cure sooner than other screening exams.
I believe it is worth the discussion with each patient on their individual cancer risks; what is the family history, personal risk factors, and current disease state of the patient? And if we choose to pursue a test like the Galleri; would you want to pursue diagnostic testing although you are asymptomatic? As always, having a discussion on what can be ordered and for what purpose is important and now seems to be even more important with multi-cancer early detection testing.
If you would like to have a discussion regarding Galleri testing at Coeur Vitality, then we are more than happy to discuss the knowns and unknowns, and ultimately make a decision together.
Citations:
1. Jannin, A. (2023, October 25). This $1,000 test finds signs of cancer in your blood. This $1,000 Test Finds Signs of Cancer in Your Blood. https://www.wsj.com/health/healthcare/this-1-000-test-finds-signs-of-cancer-in-your-blood-a7f8ee6a
2. Galleri cancer screening test performance: Galleri®. Galleri® Test. (2024, January 1). https://www.galleri.com/what-is-galleri/test-performance
3. Doubeni CA, Castle PE. Multicancer Early Detection: A Promise Yet to Be Proven. Am Fam Physician. 2023 Mar;107(3):224-225A. PMID: 36920808.
4. Imperiale T. et al: Multitarget stool DNA testing for colorectal-cancer screeningI. N Engl J Med 2014;370(14):1286-1297