A supplemental blood test for the detection of prostate cancer
There are several benefits to both patient and payer for a PSA supplemental laboratory developed test. Dr.Howard Urnovitz from Chronix Biomedical says that it makes the entire approach of screening for prostate cancer more accurate
Prostate-specific antigen (PSA) screening for prostate cancer remains contentious, regardless of indication that PSA testing substantially reduce mortality. This is in part because the risk: benefit ratio has not been fully established. Even though PSA screening has facilitated earlier detection of prostate cancer, the precise mortality benefit of early detection is unclear. In the commentary below, Dr.Howard Urnovitz explores the possibility of a supplemental blood test for detection of prostate cancer.
A significant advancement in the early detection of prostate cancer occurred in the 1970’s. Many proteins were discovered to be associated with prostate cancer. Dr. T. Ming Chu, at RPMI, NY, USA, characterized the prostate-specific antigen (PSA) and developed a blood test for its detection. It is estimated that tens of millions of men world-wide take the PSA test.
In the last 5 years, several expert panels and medical associations have recommended that healthy men should no longer receive a PSA test to screen for prostate cancer, because its high false positive rate often leads to more tests and treatments that needlessly may cause pain, impotence and incontinence in many.
The downside of recommending lesser number of PSA tests is that fewer men will detect prostate cancer at its earliest stages. Clearly new technology is necessary to meet the challenges in early detection.
First reported in 1948, a great amount of effort has taken place on establishing the clinical utility of cell-free DNA (cfDNA) in serum and plasma. The last 60 years has seen an amazing amount of information about DNA from its very double-helix structure to amplifying a single copy of DNA and to sequencing of whole genomes.
The last decade has brought us next-generation sequencing (NGS) where we have seen the process of sequencing genomes go from years and cost of billions to hours and costs of less than thousands.
Chronix Biomedical first reported in 2009 the ability to sequence entire human genomes from the cfDNA of apparently healthy individuals using NGS. These analyses require less than 10 ml of blood. We followed up in 2010 reporting how NGS could differentiate cfDNA from prostate and breast cancer patients from each other and their respective healthy controls. The time to generate the NGS sequencing results took weeks to months at a cost of tens of thousands of euros.
This year we reported on a retrospective validation study of over 400 samples from prostate cancer patients and matched controls. The study looked at serum samples from 204 patients with prostate cancer (Gleason scores 2 to 10), 207 male controls and 20 patients with benign hyperplasia or prostatitis. cfDNA was extracted from the serum and whole genome NGS was performed. Measuring the copy number imbalances of a limited number of chromosomal regions was sufficient to distinguish between prostate cancer, other prostate medical conditions and controls.
Currently, the procedure takes only days and less than a thousand euros with the cost expected to decrease with time.
Benefits of a PSA Supplemental Test
There are several benefits to both patient and payer for a PSA supplemental laboratory developed test (LDT) that makes the entire approach of screening for prostate cancer more accurate. First, utilizing the low cost PSA test to remain as the first method for screening allows for the detection of prostate cancer at its earliest stages, even at a cost of many false positive results.
Second, the addition of supplemental tests that have high accuracy in distinguishing true positives from false positives can save tens of thousands of men each year from the anxiety of unnecessary biopsies, operations, treatments with their associated adverse events, and costs. Third, the supplemental tests should be able to monitor prostate cancer patients with indolent disease as a way of surveillance of slow growing cancers, determine efficacy of treatments, and detect emergence of metastases or recurrence of cancer.
Chronix Biomedical is planning a prospective healthcare economic study to demonstrate the cost benefits of using a PSA/supplemental test approach. The objective of the study is to test as many men with an elevated PSA so as to reach statistical significance. The study should include other supplement tests and technology such as urine RNA, cellular and genetic analysis of first biopsies and imaging approaches.
Imaging approaches that may be considered are MRI or ultrasound directed biopsies under the local “standard of care.” Clearly, the challenge of this study will be to calculate positive and negative predictive values against a backdrop of high false positive PSA results and high false negative tissue biopsies.
The study needs to include a large proportion of individuals from high risk populations such as men of African-Caribbean family origin. Lastly, the study needs to include a protocol for long term surveillance especially of men with slow growing, indolent disease.
The knowledge base of breakthroughs in technology and subsequent applications to prostate cancer screening and monitoring will need to be disseminated to the very doctors, who are on the front line making decisions about screening, diagnosis, and measuring therapeutic efficacy and follow up monitoring. Government review and recommendations of the new benefits to patients and the healthcare system would have an important leadership role on the process of early detection.