Prostate cancer aggressiveness may not change over time

Prostate cancer aggressiveness may be established when the tumor is formed and does not alter with time, according to a recent study.

Researchers found that after the introduction of widespread PSA screening, the proportion of patients diagnosed with advanced-stage cancers dropped by more than sixfold in 22 years, but the proportion diagnosed with high Gleason grade cancers did not change substantially. This suggests that low-grade prostate cancers do not progress to higher grade over time.

The study adds more evidence to the argument that low-grade prostate cancer patients can safely opt for active surveillance, according to the authors.

 “We were able to look at finely stratified time periods to capture pre-PSA, early-PSA, and late-PSA eras within one study. 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,” said first author Kathryn Penney, ScD, of Brigham and Women’s Hospital in Boston. “We were surprised by just how constant the incidence of high-grade disease has been over time.”

Dr. Penney and her co-authors 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 authors reanalyzed prostate tissue collected from these patients to assess Gleason grade.

Researchers divided the data into four time periods based on when the participants received a diagnosis and treatment: 1982-1993, 1993-1996, 1996-2000, and 2000-2004, to represent the pre-PSA and PSA eras. They found that the number of participants who had undergone PSA screening increased from 42% in 1994 to 81% in 2000.

They also found that the number of late-stage cancers decreased from 19.9% in the 1982-1993 group to just 3% in the 2000-2004 group, reflecting an 85% drop in stage at diagnosis. However, there was only a moderate decrease in high Gleason grade cancers, from 25.3% in the 1982-1993 group to 17.6% in the 2000-2004 group, reflecting a 30% drop.

With further analyses, the authors found that the moderate drop in high Gleason grade cancers was not because progression to more aggressive disease was prevented through screening, but because of an increased diagnosis of low-grade disease that would not have been detected without PSA screening.

“Radical prostatectomy 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,” said Dr. Penney. “Men with low-grade disease at diagnosis should seriously consider talking with their doctors about active surveillance.”

Results from the study were published in Cancer Research (2013; 73:5163-8).

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