Biopsies Often Not Useful 2 Years After Radiotherapy for Prostate Cancer

01/11/18

By Will Boggs MD

NEW YORK (Reuters Health) - Two-year post-radiotherapy biopsies do not predict survival for most men with prostate cancer, according to results from the RT01 trial.

"Two-year biopsy is not a standard procedure and should not be recommended unless there is evidence of recurrence on MR (or perhaps PSMA-PET),” Dr. David Dearnaley from Institute of Cancer Research and Royal Marsden Hospitals, Sutton and London, UK, told Reuters Health by email.

Difficulties in interpreting post-radiation prostate biopsies and disagreement about their optimal timing have contributed to the controversy over their value in predicting prostate cancer survival and recurrence.

Dr. Dearnaley and colleagues used data from RT01, a randomized trial of radiotherapy dose escalation with 10 years of follow-up, to assess the value of 2-year post-radiotherapy treatment biopsies in men with localized prostate cancer.

Of 843 trial participants, 312 had biopsies at 2 years. Death rates were higher among non-biopsied men (172/531, 32%) than among biopsied men (64/312, 20.5%), according to the January 4 European Urology online report.

Among 177 men without a prior biochemical failure whose biopsies were reviewed centrally, independent predictors of biochemical progression-free survival (bPFS) events included 2-year biopsy outcomes, 2-year PSA, and stage T-3 or higher.

Patients with positive versus those with suspicious or negative biopsies did not differ significantly in the risk of death from any cause.

Only four prostate cancer-related deaths occurred: 1/145 patients with negative biopsies, 0/18 patients with suspicious biopsies, and 3/14 patients with positive biopsies (P=0.02).

The findings persisted in analyses of men without a prior biochemical failure whose biopsies were reviewed locally.

Prostate cancer mortality was similar and low, regardless of biopsy, among men with PSA/clinical control at 2 years (2% with and 4% without biopsy), but it was considerably higher in patients who had PSA/clinical failure, with biopsy (24%) or without biopsy (59%).

PSA values between 1.01 and 2 ng/mL at 2 years were associated with much higher positive biopsy rates (35%) than were PSA levels below 1 ng/mL (7%). In multivariate analyses, higher PSA values were associated with significantly higher risks of PSA failure, bPFS events, and prostate cancer-specific mortality.

“Men with a (low) PSA level had a very low rate of recurrence/positive biopsies and can be strongly reassured,” Dr. Dearnaley said. “Men with PSA 1.0-2.0 may be the group to target for early salvage therapy.”

Dr. Michael J. Zelefsky from Memorial Sloan Kettering Cancer Center, New York, who has also examined prognostic factors after radiotherapy for prostate cancer, told Reuters Health by email, "The authors demonstrate that even among patients with relatively low PSA values (such as between 1-2 ng/mL) at the time of such biopsies, there was a correlation with a positive biopsy and prostate-cancer specific survival outcomes. Their data suggest that among patients with very low PSA values at the time of biopsy such as <1.0 ng/mL, the biopsy was more frequently negative.”

“Given the well-known fluctuations of PSA in the post-radiotherapy setting, the post-radiotherapy biopsy, I believe, still remains a valuable tool providing important prognostic information to patients and their oncologists managing their care,” he said. “With the availability of salvage re-irradiation approaches, such as brachytherapy, with increased precision, earlier knowledge about the relapse status of a patient and earlier administration of salvage therapies may prove to be associated in the future with improved outcomes.”

SOURCE: http://bit.ly/2FfQrqr

Eur Urol 2018.

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