Improving Prostate Cancer Detection
There is controversy regarding the use of the prostate-specific antigen (PSA) test, a simple blood test, for the diagnosis of prostate cancer.
Some medical groups such as the American Cancer Society support offering PSA testing, but others including the U.S. Preventive Services Task Force (USPSTF) have issued recommendations discouraging the use of PSA testing.
Prostate cancer is the second most common cause of cancer deaths in American men, killing 38,000 men in 2012. Prior to the introduction and adoption of PSA, the majority of prostate cancer was detected because of symptoms of advanced cancer or a nodule found on a digital rectal examination. These symptomatic tumors were usually high grade, advanced and often lethal.
Part of the USPSTF decision was based on the widespread application of the PSA test to the population resulting in a high proportion of men needing to be screened and treated in order to save one life. In order to be effective and to minimize the risks of overdiagnosis and overtreatment, prostate cancer testing must be individualized based on a man’s risk factors. This is especially important for at-risk populations such as African-American men and those with a family history of the disease.
The benefits of PSA testing are decreased in older patients and those with other significant health problems that limit their lifespan. Another issue with the PSA test is that it can be altered by infection and prostate enlargement making it less specific for cancer diagnosis. With the recent controversy regarding PSA testing, the field of urology is in need of new techniques for identifying prostate cancer.
Recent work in Dr. David Jarrard’s laboratory takes advantage of one underutilized aspect of prostate cancer. Many cancers, including head and neck and bladder, are associated with molecular changes not only in the tumor but in the associated "normal appearing" tissues. This field defect may lead to cancer recurrence, but also helps to explain the frequent development of multifocal cancer seen in the prostate.
A recent study examining DNA methylation, an alteration that occurs on DNA, was performed in men with cancer and on prostate tissue from men without cancer. Screening 385,000 regions, we found 674 were altered in tumor-associated prostate tissues when compared to men without cancer.
Of interest, the distance away from the tumor did not change the extent of the methylation change. These changes were then validated in normal appearing biopsy tissue from a separate group of patients and it was found to identify those patients with cancer elsewhere in the prostate.
This new test has the potential to improve our ability to find cancer and reduce the number of biopsies required to detect it. It will decrease the need for repeated prostate biopsies, a procedure associated with cost and some risk. Furthermore, these changes may also appear in the prostate cells that are shed in the urine. Ongoing studies suggest this may lead to the development of a new method for cancer detection.
Finally, further research into this finding will likely yield additional understanding regarding how prostate cancer develops and better ways to prevent it.