While having generated a lot of buzz recently, early screening for multiple types of cancer at once may not be that ideal in practice- the path to clinical adoption could be taking on one cancer type at a time.
In a perfect world, a simple blood test would catch all cancers in early, curable stages—this is appealing specifically for cancers where there is no existing screening solution, such as pancreatic, ovarian and liver. Screening for specific cancers such as colon via colonoscopy, and skin cancer through annual physical exams save thousands of lives each year. These are existing reliable tests for specific populations, but not applicable to population screening outside their specific parameters.
The idea of developing a multi-cancer liquid biopsy assay (MCLBA) method remains controversial at best, even if highly hyped. The working theory is that the reduction of cancer incidence is farther out of reach than the reduction of cancer mortality, provided patients are caught early enough in the disease to benefit from treatment. Following this logic, early screening for cancer of any type will save millions of lives. To date, however, there are several holes in that theory.
The concept of MCLBA has some support, both from practitioners and patients. A sub set of physicians, likewise, find the idea of population-wide, multiple cancer early detection intriguing and worth investigating as a future tool in their arsenal.
But research into the value of this approach to cancer screening has yet to prove out, and most physicians don’t see its relevance to their practices. Reimbursement for such general population screenings is out of the question at the moment, and sometimes, these tests can do more harm than good.
The trouble with MCLBA
Companies providing MCLBA testing claim that by detecting signals for multiple types of cancer in blood, they can identify a higher rate of cancers in early stage. This is not always what is observed in their published data.
While perhaps not as sexy an idea, traditional preventative screening remains a reliable method. Colonoscopy, for instance, even allows doctors to remove pre-cancerous lesions, heading the disease off at the pass.
Early detection screening going after as many as 20 different types of cancer, however, has yet to pan out with such success. One of the biggest issues is that, after years of research, population-based screening for some types of cancer can result in overdiagnosis of cancers either due to a high false positive rate or for some cancer types it can miss the cancer in the earlier stage of the disease. These cancers are either non-growing, or slow growing, and would likely never cause medical problems before death from another cause. Take a cancer like prostate cancer, for instance. To date, no MCLBA has been able to prove out a case identifying this type in early stage—no benefit to mortality improvement exists.
Another problem with MCLBA is the definition of ‘early stage.’ Some company’s data combines stages one through three—most doctors will be skeptical of the value of a test that considers “early” screening as stages II or III. Current screening methods likely match or even surpass these performances in stage I or II.
There’s also the question of what types of cancer will turn up and whether or not knowing about them in an asymptomatic state is worthwhile. Indeed, if we take the example of thyroid cancer, most people would not benefit from an early detection as most of the time this is a slow progressing cancer and likely an intervention such as surgery triggered by early detection would have more side effects than waiting for the patients to be symptomatic, which may never happen during their life span.
Developing some forms of cancer can be a decades-long process, and working off the assumption that they will progress rapidly from early detection to late stage is not always accurate, and thus wide-scale testing remains unjustified. This is especially true when you consider together the stress to patients, and the path to unnecessary treatments. The end result is not more lives saved, but more resources wasted, more side effects from unneeded treatment, and the subsequent stress and fall out from a cancer diagnosis. Instead of saving lives, MCLBA can be harmful on all these levels.
Additionally, clinicians who suspect cancer in a symptomatic patient will order testing for that cancer, not a MCLBA. For instance, if a patient presents with a cough, the doctor will order a low-dose CT scan—he or she will not be suspicious of colorectal cancer or other cancers. Here, the targeted organ (lung) is quite well defined by the symptoms. Instead, the doctor will want to distinguish between lung cancer and another lung condition.
More relevant solution for patient and clinicians
For now, then, rather than putting entire populations through stressful and costly screening with no proven success rates, a better, more efficacious approach is taking on cancer one type at a time. This allows clinicians to effectively treat a specific cancer type, which remains the gold standard for now.
This is the strategy that Micronoma’s Oncobiota™ platform is employing. A blood assay that can detect deadly lung cancer at an early stage (Stage I) is much more successful and applicable to an identified, high-risk population, like heavy smokers.
With a target population for lung cancer—defined in 2021 by the U.S. Preventive Services Task Force (USPSTF) as those 50- to 80-years old with a 20-pack-a-year smoking history—the value proposition is much higher than throwing darts at any type of cancer in any population. A, readily accessible blood draw is much easier on the patient and better for the overall healthcare system.
Micronoma’s microbiome-driven blood test looks for circulating microbial nucleic acid signatures from tumors and the body’s reaction to those tumors. The blood assay is validating not just against healthy tissue, but other diseases as well. In the case of lung cancer, for instance, the Micronoma test will distinguish it from another condition, such as granuloma or fibrosis. When used with identified high-risk patients, this allows for much earlier identification of specific cancers like lung cancer, providing life-saving treatment in the beginning stage of the disease. The result is a much more survivable illness.
For now, going after cancer with this specific, targeted approach is the more cost-effective and beneficial method for helping patients survive the disease. This is Micronoma’s modular approach. In the future that may change, and the individual assay tests may assemble with one another, leading to a realistic widespread early diagnostic approach.
For now, however, patients and their doctors are much better served going after specific cancers, one at a time.