Prostate imaging, biopsy often miss contralateral tumors

Chicago-Recent research shows contemporary imaging and biopsy techniques often fail to identify contralateral tumors in men presumed to have unilateral prostate cancer-and the results have significant implications for identifying candidates for hemiablation.

A study by researchers at UCLA Health David Geffen School of Medicine found a substantial percentage of patients diagnosed with unilateral prostate cancer based on contemporary imaging and biopsy techniques harbor undetected, clinically significant contralateral disease.

Among 665 patients studied, 92 met primary criteria for hemiablation based on a review of imaging and biopsy results. However, 44 patients (47.8%) were later discovered to have contralateral prostate cancer tumors of Grade Group 2 and above on final pathology. The rate of undetected contralateral disease in candidates for hemiablation ranged from 40.8% to 47.8% depending on the inclusion criteria used.

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“We were surprised by the rate of missed tumors based on the mpMRI [multiparametric magnetic resonance imaging] results,” David Johnson, MD, MPH, who was with UCLA Health at the time of the study, told Urology Times. “We were also surprised by how robust the results were regardless of the inclusion criteria.”

Men with anterior index tumors were 2.4 times more likely to harbor undetected significant contralateral prostate cancer than men with posterior lesions, the authors found.

“It’s something we need to counsel patients on-not just that hemiablation may not treat [their cancer] completely, but also that it may not contain the cancer to begin with,” said Dr. Johnson, currently with Blue Cross NC and the University of North Carolina, Chapel Hill.

The study, presented at the 2019 AUA annual meeting in Chicago, was conducted under the direction of Robert E. Reiter, MD, of UCLA's Jonsson Cancer Center. The authors conducted a retrospective analysis of patients undergoing mpMRI with MRI-fusion prostate biopsy prior to radical prostatectomy at a single tertiary institution from June 2010 to November 2017. They identified theoretical hemiablation candidates and a range of inclusion criteria in sensitivity analyses. They also evaluated preoperative predictors of undetected contralateral disease using multivariable analysis.

“We considered a wide variety of inclusion criteria in six trials,” Dr. Johnson said.

The authors then worked to identify hemiablation candidates who were discovered to have contralateral, clinically significant prostate cancer, based on whole-mount prostatectomy pathology, and/or ipsilateral high-risk disease.

The results point to the limitations of MRI in spotting prostate tumors, Dr. Johnson said, given that nearly half the candidates for hemiablation had contralateral tumors that weren’t spotted during imaging.

“There is still sampling error from repeat biopsy and MRI that exists,” he said.

It’s important to note that one constraint of the study is the unknown clinical significance of missed contralateral disease.

Given the findings, those considering hemiablation must weigh the risk of inadequate treatment due to undetected contralateral disease against the functional benefits of hemiablation, which include less exposure of healthy tissue to treatment. Further investigation to improve patient selection for focal therapy is necessary.