To understand the risk of cancer, scientists for years have focused narrowly on changes in the concentration of a single protein in biological fluids such as blood or urine or, alternatively, on genetic mutations. However, relatively poor sensitivity, specificity and predictive value generally limit the diagnostic accuracy and clinical utility of these tests.
Screening and early detection strategies for prostate cancer in particular remain controversial because of the lack of diagnostic accuracy of serum PSA, which may lead to either missed diagnosis of clinically significant cancers or over-diagnosis of nonlethal cancers – potentially resulting in unnecessary treatment and morbidity. PSA screening is also controversial because of mixed data on its effect on mortality in screened vs. unscreened populations. Several new PSA-based tests have exhibited modest improvements in diagnostic accuracy over PSA alone. However, the statistical power of these tests for the purposes of screening and early detection remains less than optimal.
In 2016, a new biomarker platform is hitting the market that focuses on changes in the structure of certain proteins circulating in blood or other biological fluids to indicate the presence or absence of cancer. Unlike looking at genetic mutations, which can tell you the risk of cancer, the new tests can give you real-time information on the presence of cancer by evaluating the structural isoforms of protein biomarkers to differentiate those produced by cancer as compared to those produced by benign cells.
When compared with standard PSA testing for prostate cancer, preliminary results of the new structural isoform test showed 100 percent sensitivity with no false negatives and approximately 80 percent specificity. Other preliminary results in breast and ovarian cancer tests demonstrated that this new platform potentially could be used to diagnose a broad spectrum of cancers. A multicenter prospective validation trial of the prostate cancer IsoPSA test is expected to be complete in the 4th quarter of 2015 in time for market introduction in early 2016. Experts believe the platform’s inexpensive price tag-in addition to its accuracy- will lead to wide adoption in labs across the United States.
Where Are They Now
A recent trial published in April 2016 examined the ability of ctDNA analysis to detect key mutations related to non-small cell lung cancer. The trial reported detection of the majority of mutations with no false-positive readings. A separate ongoing trial focuses on a breast cancer-associated protein. In addition to these two, there are a number of protein biomarkers being explored for roles in various cancers. Early cancer screening is farther out, though researchers are actively working toward the ability to identify rare ctDNA mutations with plans to launch a “pan-cancer” screening test by 2019.