mpMRI Bx protocol may reduce repeat biopsies, but at what cost?

July 12, 2018

"Despite the potential benefits (fewer biopsies, less cost), the proposed approach to cancer detection and biopsy-that can miss 16%-40% of existing csPCa-may be difficult to justify for all patients," writes Badar M. Mian, MD.

“Journal Article of the Month” is a new Urology Times section in which Badar M. Mian, MD (left), offers perspective on noteworthy research in the peer-reviewed literature.  Dr. Mian is associate professor of surgery in the division of urology at Albany Medical College, Albany, NY.

Multiparametric magnetic resonance imaging of the prostate has been shown to enhance the diagnostic yield of prostate biopsy, especially in the setting of repeat biopsy. A clinically important question often comes up after the MRI whether the biopsy should include the MRI target only (T-PBx) or the random systematic perineal (SP-PBx) samples as well. According to a recent report by Pepe et al, the decision to perform T-PBx only when MRI showed a suspicious lesion (PIRADS ≥3) could potentially reduce the number of biopsies by 50% (J Urol April 18, 2018 [Epub ahead of print]). But it appears that over 16% of the clinically significant prostate cancer (csPCa), defined as Gleason score 7 or Gleason group ≥2, would be missed using this approach.

Also by Dr. Mian: PRECISION data lend validation to utility of multiparametric MRI

The authors identified 1,032 men who underwent repeat prostate biopsy between January 2011 and February 2018 using the perineal template saturation technique (SP-PBx). The median age was 63 years and the indication for repeat biopsy was clinical suspicion of cancer, with increasing or persistently elevated PSA (median PSA of 8.6 ng/mL). PIRADS 3, 4, and 5 were noted in 24%, 21%, and 5%, respectively, while the other 49% of men had normal MRI (or PIRADS <3).

The authors performed SP-PBx under sedation to obtain a median of 30 biopsy cores, with a range of 28-34 cores. An additional four cores were added in nearly half the patients who had an MRI lesion and underwent T-PBx. They used “visual estimation” fusion to biopsy the lesions transperineally in 229 men, transrectal fusion in 169 cases, and transperineal fusion biopsy in 126 cases. Interestingly, the report only mentions that there were no complications requiring hospital admission but the usual complications associated with prostate biopsy (hematuria, infection, hematoma, pain) are not mentioned.

Next:Rates of detection comparedRates of detection compared

Overall, prostate cancer was diagnosed in 372/1,032 (36%) men and 272/372 (73.1%) of those were classified as csPCa. Of the 272 csPCa, Gleason scores of 3+4, 4+3, 4+4, and 4+5 were identified in 112 (41.1%), 60 (22.1%), 50 (18.4%), and 50 (18.4%) cases respectively. The use of mpMRI as the reason to biopsy (ie,“a triage test”) would have spared 508/1,032 (49.3%) and 760/1,032 (73.6%) using as a cut-off a PI-RADS ≥3 or PI-RADS ≥4, respectively.

In reviewing the detection of csPCa, the SP-PBx missed 12 cases (4.5%) while the “T-PBx only approach” for all PIRADS ≥3 would have missed 44 cases (16.2%) and PIRADS ≥4 would have missed 108 clinically significant prostate cancers (39.7%).

Read: Negative Bx during AS linked with lower risk of reclassification

 

The large number of csPCa missed (false negatives) by the MRI target-only approach is concerning. It is possible that the missed csPCa may be at the lower end of the clinical significance spectrum (eg, microfocal Gleason pattern 4) but those data are not provided. Despite the potential benefits (fewer biopsies, less cost), the proposed approach to cancer detection and biopsy-that can miss 16%-40% of existing csPCa-may be difficult to justify for all patients. On an individual level, there are clearly some men who could benefit from a target-only approach; ie, those who are borderline candidates for early detection or those at above-average risk of bleeding or infection from the biopsy procedure.