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  • Writer's picturePre-Collegiate Global Health Review

Blood Tests: An Accessible, Non-Invasive Technique to Diagnose Localized Cancers

Namrata Venkatesan, Jesuit High School, Beaverton, Oregon, USA

There are over 100 types of cancer, and approximately 1 in 2 people will be diagnosed with it in their lifetime (Tanday, 2015). 608,000 lives will be taken just this year (American Cancer Society, 2021). In 2021, it is predicted that about 1.9 million new cancer cases will be diagnosed (American Cancer Society, 2021).

Too many cancer deaths occur because diagnoses are made when cancer has metastasized, or started growing at a site other than its original location. A 2019 study published in Cancer Medicine found that 60.1% of cancer deaths were due to metastatic cancers (Dillekås, Rogers, et al., 2019). Metastasis occurs when the primary tumor escapes its location, usually through the bloodstream or lymphatic system, through a process known as intravasation. Infiltration of the bloodstream grants cancer cells access to essential organs and lymph nodes, as shown in Figure 1, making it more difficult to treat and eliminate these cancers.

Figure 1. Metastasis: when cancer spreads.

So how can we detect cancers when they are still localized in its early-stages?

Johns Hopkins researchers Bert Vogelstein, Kenneth Kinzler, and Nikolas Papadopulos may have developed a potential solution: CancerSEEK. While not yet available for hospital use, CancerSEEK is a liquid biopsy that is intended to diagnose cancer patients before they display any symptoms. In short, it is a blood test. CancerSEEK scans the DNA in a blood sample for genetic mutations and proteins that can be indicative of cancer. Currently, the biopsy can diagnose eight of the world’s most prevalent cancers, even if patients are asymptomatic (Johns Hopkins Medicine Newsroom, 2018).

CancerSEEK is unique not only because of its ability to accurately diagnose asymptomatic cancers, but also because of its non-invasive nature. Taking colorectal cancer as an example, one of the most common and accurate screening methods for colorectal cancer are colonoscopies (American Cancer Society, 2021). Though the procedure has an accuracy rate of 94%, colonoscopies are invasive procedures that require sedatives just like any other surgery, often resulting in complications or allergic reactions to the anesthesia (Mayo Foundation for Medical Education and Research, 2020; North Shore Gastroenterology, 2021).

CancerSEEK is still in its working stages, but ThriveDetect, a company dedicated to diagnosing cancer early (especially those that have no screening procedures), asserted that the test “identified 65% of cancers at earlier stages and identified cancers across 10 organs, seven of which have no recommended standard-of-care tests” (Thrive, 2020). While the test has resulted in false positives, those who receive a positive test can undergo further diagnostic testing to determine whether they have cancer or not.

It is also possible to test for circulating tumor cells (CTCs) in the bloodstream. These are cells that have detached from a tumor and are simply flowing in the bloodstream. While some CTCs evolve to form tumors in different parts of the body, they often remain present in the blood. Currently, the CellSearch Circulating Tumor Cell Test, an FDA-approved procedure, assists in the diagnosis of colorectal, breast, and prostate cancers (Mayo Clinic, 2013). Though the test can only be used in metastatic cancers, a study published in 2009 determined that the CTC test was reliable in diagnosing metastatic breast, colorectal, and prostate cancers (Miller, Doyle, et. al., 2009).

These novel cancer-screening blood tests could significantly reduce the number of deaths from late-stage diagnosis in developing countries, as opposed to traditional screening methods, because they are more cost-effective and do not require specialized medical or surgical equipment. Routine screening procedures, such as MRIs and X-rays, can cost anywhere from $500 to $1,000; in many countries, this amount is unrealistic for a single medical test (ABIM Foundation, 2015). Because these tests and scans are so expensive, those who are at risk are less likely to seek diagnostic exams and medical treatment because they do not have the funds to pay for it. Any blood test, even if it screens for cancer, would be much more affordable and attainable.

These blood tests would also benefit countries with universal health coverage. Usually, only those who are at a high risk for cancer would qualify for expensive diagnostic tests because they are covered by the government. Making tests more affordable would expand accessibility for those who are at a lower risk. On another front, those without sophisticated healthcare systems in their home country must travel to a different country in order to seek the level of care they need. With a blood test, these patients would not have to leave their home country to get diagnosed due to its increased accessibility.

With any medical procedure that requires anesthesia or any amount of recovery time, there is also an inherent fear about having to take a day off work for people who get paid on a day-to-day basis. A blood test would take minutes, while routine procedures like colonoscopies, could potentially take hours with a recovery time of a few days. Blood samples are also convenient because they can be done at a rural hospital and be sent to a different location for analysis, making them accessible anywhere and everywhere.

In the last 50 years, the world has made significant progress in developing innovative treatments for cancer, such as targeted therapies and personalized medicine. But no matter how sophisticated a treatment is, chemotherapy and immunotherapy are often not curative for metastasized cancers. Diagnosing cancers early significantly improves the patients’ survival odds, and cancer-detecting blood tests may just be the key towards revolutionizing the future of cancer diagnosis.



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Johns Hopkins Medicine. (2018, January 18). Single blood test screens for eight cancer types. Johns Hopkins Medicine Newsroom. Retrieved October 17, 2021, from

Johns Hopkins Technology Ventures. (2020, November 6). Thrive releases results of first study on Multicancer Blood Test. Johns Hopkins Technology Ventures. Retrieved October 17, 2021, from

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Mayo Foundation for Medical Education and Research. (2020, April 18). Colonoscopy. Mayo Clinic. Retrieved October 17, 2021, from

Miller, M. C., Doyle, G. V., & Terstappen, L. W. M. M. (2010). Significance of circulating tumor cells detected by the CellSearch system in patients with metastatic breast colorectal and prostate cancer. Journal of Oncology. Retrieved October 17, 2021, from

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Team, M. C. (2021, February 5). Colon cancer and rectal cancer screening: What are my options? American Cancer Society. Retrieved October 17, 2021, from

Thrive - An Exact Sciences Company. (2020, October 9). Detect cancer as early as possible: CancerSEEK - Thrive Detect. Thrive. Retrieved October 17, 2021, from


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