Higher reclassification rate seen with saturation biopsy

Boston-Transrectal saturation biopsy resulted in higher rates of disease reclassification compared with magnetic resonance (MR) fusion biopsy plus extended sextant prostate biopsy in patients with low-risk prostate cancer on active surveillance.

In a review of 228 unique biopsy encounters from 177 men initially managed by active surveillance at Cleveland Clinic, the reclassification rate was about double with saturation biopsy than with MR target only or MR target plus extended template biopsy, reported Yaw Nyame, MD, MBA, at the AUA annual meeting in Boston, in a project that is mentored by Ahmed Elshafei, MD, PhD, and J. Stephen Jones, MD, from Cleveland Clinic.

Active surveillance as a management strategy has increased considerably over the past decade. In the ProtecT study, about 50% of the men who chose active surveillance as a strategy for management of localized prostate cancer received an intervention during the 10-year follow-up, driven in part by disease reclassification.

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In a large prospective study, Siddiqui et al found that among men undergoing biopsy for suspected prostate cancer, targeted MR/ultrasound fusion biopsy was associated with increased detection of clinically significant prostate cancer compared with standard extended-sextant ultrasound-guided biopsy (JAMA 2015; 313:390-7). Dr. Elshafei and colleagues found that up to 18% more cases of clinically significant cancer could be detected using multiparametric MR compared with standard transrectal ultrasound biopsy.

Dr. Nyame“However, there are mixed results from recent studies looking at MR in active surveillance cohorts, with most recently the UCSF group demonstrating that there is more reclassification detected on the extended biopsy portion of their combined MR fusion and ultrasound biopsies,” said Dr. Nyame, urology resident at Cleveland Clinic’s Glickman Urological and Kidney Institute. “Additionally, any time you have a new technology, you have to factor in the cost and expertise as significant barriers in times to entry for certain practitioners.”

The authors hypothesized that transrectal saturation biopsy could provide similar rates of disease reclassification compared with multiparametric MR-guided biopsy in patients receiving confirmatory or surveillance biopsy while on active surveillance.

Next: 228 biopsies reviewed

From their institutional prostate biopsy database, they reviewed 228 unique biopsies (53 MR fusion biopsies and 175 transrectal saturation biopsies) from 177 men diagnosed with low-risk prostate cancer who chose active surveillance. Inclusion criteria were low-volume, low-risk disease as defined by the National Comprehensive Cancer Network and receipt of at least one confirmatory or surveillance biopsy performed at Cleveland Clinic and transrectal saturation biopsy or multiparametric fusion biopsy plus a systematic biopsy.

Reclassification rates were compared using simple descriptive statistics. Reclassification was defined as progression to Grade Group 2 prostate cancer or more than 33% cores positive.

The mean age at diagnosis was 67 years and the median PSA level at diagnosis was 5.4 ng/mL. Some 8.7% of the men self-identified as African-American.

Within the group receiving confirmatory biopsy, “We found that 44% of patients that had transrectal saturation biopsy had disease reclassification compared to 12% on target only and 20% on combined target plus extended template biopsy, and this difference was statistically significant,” Dr. Nyame said.

Reclassification rates compared

Within the group receiving surveillance biopsies, the rate of reclassification was significantly greater with saturation biopsy compared with MR target biopsy only (44.0% vs. 11.3%, p<.001) and also compared with MR target plus extended template biopsy (44.0% vs. 24.5%, p<.01).

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Dr. Nyame emphasized that the cohort of patients was small, especially among the group receiving MR fusion biopsy.

“If we had one more reclassification on one more MR fusion biopsy, we would have a significant increase in the percentages that we’re comparing,” he said. “So we must be careful to not overstate the difference that we see between the two groups.”

In addition, MR fusion and multiparametric MR are highly dependent on expertise, and therefore early cases may under-represent the diagnostic accuracy of multiparametric MR.

“I think that our findings should make clinicians consider transrectal saturation as being a cost-effective alternative for confirmatory and surveillance biopsies, and more research is needed to better understand the utility of MR in patients managed by active surveillance. Maybe saturation biopsy can serve as a tool to be utilized by practitioners that may not currently have access to MR technology,” said Dr. Nyame.

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