Data analyzed from a large cohort study of men diagnosed with prostate cancer found that prostate cancer aggressiveness may be established when the tumor is formed and not changed over time. The researchers of the study, Kathryn L. Penney, ScD, Instructor in the Department of Medicine at Harvard Medical School and Associate Epidemiologist at Brigham and Women’s Hospital, and colleagues compared data from 420 participants recruited to the Physicians’ Health Study and 787 participants recruited to the ongoing Health Professionals Follow-up Study. All of the men were diagnosed with prostate cancer between 1982 and 2004 and treated with prostatectomy.
The researchers determined that after the first introduction of widespread prostate-specific antigen (PSA) screening, the proportion of patients diagnosed with advanced-stage cancers was reduced by more than sixfold in 22 years, but that the proportion diagnosed with high Gleason-grade cancers did not change substantially. The findings suggest that low-grade prostate cancers do not progress to higher grade over time. The study is published in Cancer Research.1
Pre-PSA vs PSA Eras
To compare the distribution of grade and clinical stage across the pre-PSA and PSA screening eras, the 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.
They found that the number of men who had undergone PSA screening increased from 42% in 1994 to 81% in 2000, and that the number of late-stage cancers decreased from 19.9% in the 1982-1993 group to only 3% in the 2000–2004 group, reflecting an 85% decrease in stage at diagnosis. However, there was just 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% decrease.
Further analysis of the data found that the moderate decrease 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. ■
Disclosure: The study authors reported no potential conflicts of interest.
1. Penney KL, et al: Cancer Res. August 15, 2013 (early release online).