ORLANDO, Fla.—Patients on active surveillance for prostate cancer (PCa) are more likely to have pathologic upgrading on repeat biopsy if they have intermediate-risk rather than low-risk disease at baseline, researchers reported at the annual Genitourinary Cancers Symposium.

The finding is based on what the investigators said is the largest re-biopsy cohort with long-term follow-up described to date, enabling the first estimates of PCa dedifferentiation in patients on AS.

The cohort included 593 men who had at least one repeat biopsy. The median follow-up was 6.4 years (maximum 20.2 years). The total number of biopsies ranged from two to six. Of the total cohort, 79.7%, 20%, and 0.3% had low-, intermediate-, and high-risk disease at baseline, respectively.

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Investigators Suneil Jain, MD, of Sunnybrook Health Sciences Centre in Toronto, and colleagues found that 31.3% of patients experienced pathologic upgrading during AS. The proportion of patients upgraded increased with time, suggesting PCa dedifferentiation occurred at a rate of 1% per year, Dr. Jain and colleagues reported. The estimated rate of increase was 1.9% per year in patients with intermediate-risk disease compared with 0.75% per year in those with low-risk disease at diagnosis.

In addition, the study showed that 62% of upgraded patients went on to have active treatment. Patients who were upgraded and treated had significantly greater PSA velocities (median 1.2 ng/mL per year) than those who remained on AS (0.42% per year). They also had a significantly higher proportion of patients with Gleason 8-10 tumors (21.8% vs. 2.8%).