We often see recommendations that MRI-guided biopsies may be more accurate that transrectal ultrasound (TRUS)-guided biopsies in the diagnosis of prostate cancer. A new systematic review has attempted to assess the current status of data supporting or refuting this recommendation.
Moore et al. have conducted a systematic review of published data through December 31, 2011. Their goal was to use the available evidence to offer responses to two questions:
- When MRI was applied to biopsy-naive men, what percentage showed abnormalities suggesting the need for biopsy?
- When an MRI-targeted biopsy was utilized, what percentage of patients had prostate cancer detected?
The authors report that, based on their review of the available data:
- The total number of cases available for review was 4,222.
- Only 50 cases specifically compared MRI-targeted and standard transrectal biopsy results in the same patients.
- Among all biopsy-naive men, 374/599 (62 percent) had abnormalities visible on MRI that suggested biopsy.
- Among men who underwent an MRI-targeted biopsy, 248/374 (66 percent) had prostate cancer detected.
- MRI-targeted and standard biopsies both detected the same number of cases of clinically significant prostate cancer.
- MRI-targeted biopsy detected 236/555 cases (43 percent).
- Standard biopsy detected 237/555 cases (43 percent).
- MRI-targeted and standard biopsies also bothe missed the same number of cases of clinically signifciant prostate cancer.
- MRI-targeted biopsy missed 13/555 cases (2 percent).
- Standard biopsy missed 12/555 cases (2 percent).
- MRI-targeted biopsy required fewer biopsy cores than standard biopsy
- The average (mean) number of cores taken under MRI-targeted biopsy was 3.8.
- The average (mean) number of cores taken under standard biopsy was 12.
- MRI-targeted biopsy avoided diagnosis of clinically insignificant cancer in 53/555 patients (10 percent) among the presenting population.
Moore et al. conclude that:
- MRI-guided biopsy is capable of detectecting clinically significant prostate cancer in about the same number of men as a 12-core standard biopsy.
- MRI-guided biopsy achieves this level of accuracy with fewer biopsies in fewer patients, and with a reduction in the number of diagnoses of clinically insignificant cancer.
However, they make the clear point that there is considerable variability in the methodologies used in the studies carried out and reported to date, and that what is really needed — to know whether MRI-targeting of prostate biopsies is now a sound and viable clinical strategy — is a robust, multi-center clinical trial based on a standardized protocol for the application of MRI-targeted biopsy compared to standard 12-core biopsy.
The other unanswered question (which is not addressed at all in this study) is whether transrectal color Doppler ultrasound-guided biopsy is either “better” than “gray-scale” TRUS-guided biopsy and/or comparable to MRI-targeted biopsy.