Beep. Beep. Beep. Shhhh. Whoosh. Beep. These noises fill the sterile cold hospice room. Benevolent Uncle Ted lies unconscious with a steady drip of pain relieving medicines entering his once muscular arms via an IV. Uncle Ted has prostate cancer that spread throughout his body. As the curtain slowly closes on young Uncle Ted’s life, one wonders, “If the cancer had been found sooner, would Uncle Ted be playing with his kids, sailing, hiking or enjoying a fine wine with friends and family right now?”
This sentiment is a commonly held belief. But what if screening yields many false positives and could cause more harm than good? Recently, the U.S. Preventive Services Task Force has recommended that people who are not at high risk forgo screening for thyroid cancer. It was found that in places where over diagnosis occurs, patients have undergone surgeries to remove growths found on the thyroid, but the overall number of thyroid cancer-related deaths remains unchanged. Also, the patients getting the growths removed were undergoing unnecessary treatment that carried the potential of causing more harm than good (Jin, 2017).
With prostate cancer, the same holds true. Out of 1000 men, 100 to 120 men may get a false-positive result, which leads to further testing and biopsies (National Cancer Institute, 2017a). The biopsy procedures are not without risk and the description of the procedures would cause most men to cringe (National Cancer Institute, 2017b). With all this prostate screening, only about 0.1% may have benefitted from the early screening (National Cancer Institute, 2017a). Maybe a more definitive test that does not require biopsies could be developed and save more lives?
International efforts are underway to probe easily acquired samples, such as blood and urine, to identify better biomarkers that could identify individuals with deadly prostate cancer. In these samples, researchers are targeting exosomes (small packages that originated from cells, such as prostate cancer cells, that are full of proteins that may be useful biomarkers). After optimizing a protocol for harvesting exosomes, one group identified several biomarker candidates from individuals with metastatic prostate cancer using the SOMAscan assay (Welton et al., 2016). Another group also used the SOMAscan assay to examine exosomes (originated from prostate cancer cell lines) and found biomarker candidates for prostate cancer (Webber et al., 2014). The biomarkers identified by both groups could one day be used to screen men to determine if they have the deadly prostate cancer. While the work is very encouraging, further evaluation is still needed.
With the SOMAscan assay yielding valuable insights into one’s health, the number of unnecessary risky (and cringe-worthy) medical procedures could go down. Also, people may learn of detrimental diseases earlier through the non-invasive testing. If Uncle Ted had the opportunity, he may have found himself in a different scenario at the closing of his life story.
Jin, J. (2017). Screening for thyroid cancer. JAMA, 317(18), 1920. doi:10.1001/jama.2017.5254
National Cancer Institute (2017a). Benefits and Harms of PSA Screening for Prostate Cancer. Retrieved from https://www.cancer.gov/types/prostate/psa-infographic.
National Cancer Institute (2017b). Prostate-Specific Antigen (PSA) Test. Retrieved from https://www.cancer.gov/types/prostate/psa-fact-sheet.
U.S. Preventive Services Task Force (2017). Final Evidence Review: Thyroid Cancer: Screening. Retrieved from https://www.uspreventiveservicestaskforce.org/Page/Document/final-evidence-review159/thyroid-cancer-screening1
Webber, J., Stone, T. C., Katilius, E., Smith, B. C., Gordon, B., Mason, M. D., . . . Clayton, A. (2014). Proteomics analysis of cancer exosomes using a novel modified aptamer-based array (SOMAscan) platform. Mol Cell Proteomics, 13(4), 1050-1064. doi:10.1074/mcp.M113.032136
Welton, J. L., Brennan, P., Gurney, M., Webber, J. P., Spary, L. K., Carton, D. G., . . . Clayton, A. (2016). Proteomics analysis of vesicles isolated from plasma and urine of prostate cancer patients using a multiplex, aptamer-based protein array. J Extracell Vesicles, 5, 31209. doi:10.3402/jev.v5.31209