Multicancer screening tests: Not ready for prime time
Click Here to Manage Email Alerts
Scientists have made amazing advances in recent years in understanding the molecular biology of cancer.
Despite these advances, a simple blood test to screen patients for early detection of cancer is not yet an approved option.
Articles in the media might lead people to think otherwise. “This new test for cancer could save your life” and “Multicancer early detection must be available for all” are among headlines that appeared this summer in opinion articles in USA Today.
As cancer physicians, we look forward to the day when a single blood test can screen for a wide variety of cancers. Unfortunately, that day has not yet arrived.
Finding any cancer at an early stage leads to better survival and reduced suffering. The best diagnostics we have are screening mammography for breast cancer and colonoscopy for colorectal cancer. The use of low-dose CT scanning for the early detection of lung cancer is benefiting high-risk patients.
Critical issues
Many cancers have a low prevalence in our population and, unfortunately, no screening methods for them are available. This has spurred scientists to look for new, cost-effective detection methods, including blood tests.
One possibility involves technology that gleans information from circulating DNA in the blood. As cancer cells die, they shed their abnormal DNA into the bloodstream. These DNA fragments create a signature of cancer and may even indicate the type of malignancy present.
Preliminary results of these tests are encouraging, but several hurdles must be overcome before they can be widely used. They include resolving diagnostic sensitivity issues related to DNA analysis so we can know when a positive test truly indicates cancer and when a negative test can be trusted to reassure good health. Another critical issue is that none of the multicancer diagnostic tests touted in the news have demonstrated whether they can reduce mortality rates.
Discovering a blood test that could detect multiple cancers would truly transform medicine. This minimally invasive approach could be immensely beneficial to patients and deliver enormous cost savings. Tests could be performed in a community setting and integrated into routine care by primary care physicians.
For these reasons, we must continue research efforts to find a multicancer blood test for early detection of cancer.
Essential criteria
We eagerly await the results of large-scale clinical trials that will evaluate the safety and efficacy of these tests. Once a screening test indicates a potential cancer, more invasive diagnostic tests such as tissue biopsies will be necessary to confirm the diagnosis.
In summary, any multicancer screening blood test must:
- be specific and sensitive enough to detect clinically relevant malignancies at the earliest stage possible;
- detect early-stage cancers across all major cancer types;
- identify cancers that will extend survival;and
- avoid detection of premalignant and benign tumors that may never cause harm.
Before any multicancer screening blood test is ready for prime time, it must meet these four criteria. Until that happens, more research is needed.
References:
- Greenwood J. This new test for cancer could save your life. Here's why you can't get it. USA Today. July 28, 2021. Available at: https://www.usatoday.com/story/opinion/2021/07/28/why-new-breakthrough-test-cancer-still-isnt-u-s-market/5383725001/. Accessed Aug. 17, 2021.
- Teixeira J. Multi-cancer early detection must be available for all. USA Today. July 9, 2021. Available at: https://www.delawareonline.com/story/opinion/2021/07/09/new-advances-early-cancer-screening-must-made-available-all/7896319002/. Accessed Aug. 17, 2021.
For more information:
Nicholas J. Petrelli, MD, FACS, can be reached at npetrelli@christianacare.org.
Gregory A. Masters, MD, can be reached at gregory.masters@usoncology.org.
Collapse
Click Here to Manage Email Alerts