BOSTON, Aug. 15 (UPI) -- A U.S. study adds more evidence that men diagnosed with low-grade prostate cancer can opt for an active surveillance and may never be treated, researchers say.
Kathryn Penney, an instructor in medicine at the Harvard Medical School and associate epidemiologist at the Channing Division of Network Medicine at Brigham and Women's Hospital in Boston, said after the introduction of widespread prostate-specific antigen screening, the proportion of patients diagnosed with advanced-stage cancers dropped by more than six-fold in 22 years.
However, the proportion diagnosed with high Gleason grade cancers did not change substantially. Cancer stage refers to the extent or spread of the disease, and cancer grade, called Gleason grade for prostate cancer, refers to the aggressiveness of the disease.
"We were able to look at finely stratified time periods to capture pre-PSA, early-PSA, and late-PSA eras within one study," Penney said in a statement.
"Over time, because of PSA screening, men have been more likely to be diagnosed with prostate cancer at an earlier stage, before the disease has had an opportunity to grow and spread. If Gleason grade also progressed over time, we would expect a similar decrease in high Gleason grade disease over time. But, we were surprised by just how constant the incidence of high-grade disease has been over time."
Penney and colleagues used data from 420 participants recruited to the Physicians' Health Study and 787 participants recruited to the ongoing Health Professionals Follow-up Study. All participants were diagnosed with prostate cancer between 1982 and 2004, and treated with surgery. The researchers reanalyzed prostate tissue collected from these patients to assess Gleason grade.
The researchers found the number of participants who had undergone PSA screening increased from 42 percent in 1994 to 81 percent in 2000.
The study, published in the Cancer Research, found a moderate drop in high Gleason grade cancers was not because progression to more aggressive disease was prevented via screening, but because of an increased diagnosis of low-grade disease. Prostate cancer aggressiveness established at diagnosis did not alter change over time, the study said.
"Radical prostatectomy (prostate removal) or radiation therapy, the usual treatments for prostate cancer, can have negative side effects such as impotence and incontinence; choosing active surveillance could prevent this decline in quality of life," Penney said. "Men with low-grade disease at diagnosis should seriously consider talking with their doctors about active surveillance."
