The finding, published in the journal Cancer Research, could significantly help predict prostate cancer progression.
One of the authors of the study, John Cheville, M.D., Mayo Clinic pathologist, said:
"This is the first study to examine DNA alterations using next generation sequencing in adjacent Gleason patterns in the same tumor allowing us to correlate genomics with changes in pathology."
A numerical scoring system, called the "Gleason grading system", is the conventional way of evaluating the prognosis of men with prostate cancer. When pathologists examine prostate tumor samples under a microscope, they use the Gleason score based upon the tumor's microscopic appearance and pattern of its cells.
Considering that prostate cancers usually have more than one pattern, the Gleason score is measured using the two most common patterns added together. A higher Gleason score means the cancers are more aggressive and have a worse prognosis.
Prostate cancer: The Gleason Grading System Explained
According to a 2007 Cancer publication, an increasing PSA velocity was associated with Gleason score 7-10 disease versus Gleason score 2 to 6 or no cancer.
This study focused on a Gleason score of 7 (patterns of three and four) which indicates a high risk of progression.
Dr. Cheville said: "While each pattern had its own breakpoints, they shared identical ones, which implies a common origin."
Changes in DNA which are linked to aggressive prostate cancer were already present in the lower Gleason pattern, this means that genomic changes occur before a pathologist can recognize it. Cheville said that doctors will be able to predict cancer progression by understanding these lineage relationships within a tumor.
This will help improve patient management and surveillance.
The team used laser capture micro dissection, whole genome amplification and next generation sequencing to find the relationships among the Gleason patterns of each tumor. A total of 14 tumors were studied, where they found over 3,000 unique chromosomal alterations; 300 of the alterations were shared in at least two of the tumors.
In addition, they found that there were more alterations in Gleason pattern 3 among patients with a Gleason score of 7 compared to to other patients.
A previous study published in the Proceedings of the National Academy of Sciences (PNAS), identified two inherited-genetic deletions in the human genome associated to the development of prostate cancer.
Written by Joseph Nordqvist