New $100 Genetic Test Identifies Men Who Have Vastly Increased Chance Of Developing Prostate Cancer
A new DNA “spit test” for prostate cancer can identify men who have an increased risk of developing the disease.
The research published today in Nature Genetics, funded by an international team including the world’s two biggest cancer research agencies, the National Cancer Institute (NCI) and Cancer Research UK, studied the DNA of 140,000 men to look for genetic variants that predicted for the development of the disease.
In the general population, men have around a 1-in-10 chance of developing prostate cancer and over 3 million men are currently living with prostate cancer in the U.S. Deaths from most cancer types have been steadily decreasing, but a recent report by the NCI found that the incidence of late-stage prostate cancer was increasing and that after decades of decline, mortality rates had plateaued.
The study found 1-in-100 men were almost 6 times more likely than the general population to develop prostate cancer, giving them a 50% chance of developing the disease. One-in-ten men had a 25% chance of developing the disease,
“We have shown that information from more than 150 genetic variants can now be combined to provide a readout of a man’s inherited risk of prostate cancer,” said Rosalind Eeles, Professor of Oncogenetics at the Institute of Cancer Research in London.
These DNA variants known as SNPs (single nucleotide polymorphisms) are a single letter change of DNA inherited from parents and naturally vary among individuals. Recent advances in DNA sequencing have allowed scientists to look closely at these variants and correlate them with the chances of developing several different diseases. In this study, the researchers used Illumina’s “Oncoarray” technology to look at half a million SNPs in the DNA of 80,000 prostate cancer patients and to compare these to 61,000 men without the disease.
Having each SNP only increases the chance of developing prostate cancer slightly, but having several may have a fairly strong effect on the risk of developing the disease. More than 100 of these SNPs predicting for prostate cancer occurrence were already known, but the new study adds another 63, making the predictions scientists can make with any test much stronger and more reliable.
“If we can tell from testing DNA how likely it is that a man will develop prostate cancer, the next step is to see if we can use that information to help prevent the disease,” said Eeles.
Eeles explains that they now plan to start a study with primary care physicians in the UK to see whether their genetic test, using only a saliva sample, can predict which men can benefit from interventions to diagnose the disease earlier, or even reduce the risk of the disease occurring.
“We are interested in doing similar trials to the UK and are aiming for within the next year or so,” said Fredrick Schumacher, lead author of the study and Associate Professor in the Department of Population & Quantitative Health Sciences at Case Western Reserve University in Cleveland.
Schumacher explains how the research was largely done on historical data from people of European descent, so before it can be effectively used in the U.S. the researchers need to check that the findings are relevant.
“We have more of a multi-ethnic population here in the U.S. We need to validate the test in African-American populations, particularly, as we know they are twice as likely to develop prostate cancer as people of European descent,” said Schumacher.
Schumacher and collaborators from the University of Southern California are currently in the process of analyzing data from 20,000 African American men to figure out whether the test is also useful for them and he stresses the importance of also looking at data from men from Latino and Asian American descent to ensure any test would be useful.
Importantly, Schumacher confirms the DNA analysis is likely to cost under $100, approximately similar to the cost of the widely-used, blood-based Prostate-Specific Antigen (PSA) test to monitor for prostate cancer development, which has proven controversial.
Last week, new research presented at the American Society of Clinical Oncology showed that only a minority of men with prostate cancer respond to immunotherapy, likely those men whose cancers have defects in genes involved in repairing DNA.
Many of the new genetic variants found in this study were in genes that regulate communication between cells of the immune system and other cells in the body or DNA repair, which could have future implications for treatment with immunotherapies for these patients.
“This study gives us important information about the causes of prostate cancer and the potential role of the immune system, which could ultimately be employed in the design of new treatments. We are on the cusp of moving from theory to practice – from explaining how genetics affects prostate cancer risk to testing for genetic risk and attempting to prevent the disease,” said Professor Paul Workman, Chief Executive of the Institute for Cancer Research.