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SEEKing Signs of Cancer

Written by Alexander Egipto and Edited by Myra Ali

Although a myriad of diseases and illnesses can each produce a different set of symptoms, each one leaves those afflicted with the same hope: I want to be healed. While medicine is a profession of healing, it is a profession of prevention as well, where a patient’s health is prioritized and where learning how to anticipate and detect diseases can be just as critical to saving lives as curing them. Recent research from the John Hopkins University School of Medicine has produced a new cancer-detection test dubbed CancerSEEK with some attractive qualities. As a blood test, CancerSEEK is relatively noninvasive compared to currently approved methods such as colonoscopies; it is also accurate, detecting eight of the most common cancers in western populations with a percentage sensitivity ranging from 69% to 98% depending on the cancer [1].

The most widely used blood test for cancer detection involves looking for a molecule specific to the prostate to detect prostate cancer—while the test has its benefits, the downsides are much more immediate and potentially outweigh these benefits. A particularly significant downside is the increased diagnosis and subsequent treatment of cancers that are non-lethal; such treatments cause harmful side effects and additional stress on the patient [2]. Some blood tests use free-floating DNA from tumors to identify common cancer-inducing DNA mutations in patients; studies show that these tests run the risk of increased false positive results, given that those mutations can also occur in healthy patients [3].

In contrast to these methods, CancerSEEK’s effectiveness is thanks to a combination of genetic and protein-based methods of detecting signs of cancer. The former is centered around using amplicons—these are pieces of DNA or RNA that are products of repeated gene duplication or amplification, a common process in human cancers [1]. Examining 61 amplicons, the researchers sought to detect at least one “driver gene” mutation in each cancer, which “drives” or starts the increased cell proliferation so often indicative of cancer [4]. The results were far more promising than expected, with the researchers detecting mutated driver gene DNA from a larger fraction of tumors than anticipated. The latter method focuses on detecting proteins made by the eight cancer types; this is particularly useful because while many early-stage tumors do not release free-floating DNA, they will eventually make proteins that can help identify them [1]. The researchers found eight specific proteins that helped differentiate cancer patients from healthy patients. Finally, using an algorithm that takes into account these proteins, the detected tumor DNA, and the patient’s gender, the researchers narrowed down the cancer’s original location in the body to two anatomic locations in 83% of patients, and to one anatomic location in 63% of patients [1]. This is immensely useful for when the physician needs to follow up with a patient, as knowing the anatomical origin of the cancer reveals what kind of cancer it is, and subsequently what steps need to be taken to treat it.

With cancer as the second leading cause of death around the globe in 2018, early detection tests such as CancerSEEK become all the more important in saving patients’ lives [5]. The proverb “an ounce of prevention is worth a pound of cure” comes to mind—while surgeries and therapy plans are capable of saving those afflicted, winning the fight against cancer before it even starts saves time, money, and lives that would otherwise be lost to this disease. 

References:

  1. Cohen J, Li L, Wang Y, Thoburn C, et al. 2018. Detection and localization of surgically resectable cancers with a multi-analyte blood test. Science 359: 926-930.
  2. Pinsky P, Prorok P, Kramer B. 2017. Prostate Cancer Screening – A Perspective on the Current State of the Evidence. New England Journal of Medicine 376: 1285-9.
  3. Cree I, Uttley L, Woods H, Kikuchi H, et al. 2017. The evidence base for circulating tumour DNA blood-based biomarkers for the early detection of cancer: a systematic mapping review. Bmc Cancer 17: 697-714.
  4. Tokheim C, Papadopoulos N, Kinzler K, Vogelstein B, et al. 2016. Evaluating the evaluation of cancer driver genes. Proceedings of the National Academy of Sciences of the United States of America 113: 14330-5.
  5. “Cancer.” World Health Organization, World Health Organization, 12 Sept. 2018, www.who.int/news-room/fact-sheets/detail/cancer.

Published in Medicine

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