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Low-grade prostate cancer did not develop aggressively over time
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The aggressiveness of prostate cancer can be determined at tumor formation, as low-grade disease likely will not progress to higher grade over time, according to study findings published in Cancer Research.
Prior studies have been unable to establish whether prostate tumors arise well differentiated and then develop into less differentiated forms, or whether Gleason grade is an early and largely static feature.
Kathryn L. Penney
“If Gleason grade progresses, one would expect a similar reduction in high-grade tumors considering that tumors are now detected so much earlier in their natural history than before screening,” Kathryn L. Penney, ScD, associate epidemiologist at the Channing Division of Network Medicine at Brigham and Women’s Hospital, and colleagues wrote. “One difficulty in such a comparison is that Gleason grading standards have shifted over time, so that scores below 6 are now rarely assigned, and assigning a higher grade has become more common.”
Penney and colleagues evaluated the alteration in distribution of re-reviewed Gleason scores in patients from two prospective cohorts (n=1,207). All patients were diagnosed with prostate cancer between 1982 and 2004, and they all underwent surgery.
Although the percentage of men who received PSA screening nearly doubled between 1994 and 2000, the number of diagnosed advanced-stage tumors dropped 85% over the study period, from 19.9% in 1982-1993 to 3% in 2000-2004.
However, Gleason scores decreased only 30% during the same period, from 25.3% in 1982-1993 to 17.6% in 2000-2004.
The findings suggest low-grade prostate cancers do not progress to higher grade over time, providing additional evidence that patients who are diagnosed with low-grade disease can choose a “watch and wait” approach rather than undergoing immediate treatment.
“The moderate decrease in the proportion of high-grade cases may be due to the increased diagnosis of low-volume, nonprogressing disease — cases that would otherwise never have been detected if not for PSA screening,” Penney and colleagues wrote. “These additional cases are more likely to be indolent and therefore low-grade disease. Thus, the analysis of absolute incidence of Gleason 8 to 10 over time provides a better assessment of change, and showed little evidence for a decrease.”
Disclosure: The researchers report no relevant financial disclosures.
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