Background
There is growing interest to implement multiparametric magnetic resonance imaging (mpMRI) and MR-guided biopsy (MRGB) for biopsy-naïve men with suspected prostate cancer.
Objective
Primary objective was to compare and evaluate an MRI pathway and a transrectal ultrasound-guided biopsy (TRUSGB) pathway in biopsy-naïve men with prostate-specific antigen levels of ≥3 ng/ml.
Design, setting, and population
A prospective, multicenter, powered, comparative effectiveness study included 626 biopsy-naïve patients (from February 2015 to February 2018).
Intervention
All patients underwent prebiopsy mpMRI followed by systematic TRUSGB. Men with suspicious lesions on mpMRI also underwent MRGB prior to TRUSGB. MRGB was performed using the in-bore approach.
Outcome measurements and statistical analysis
Clinically significant prostate cancer (csPCa) was defined as grade group ≥2 (Gleason score ≥3 + 4) in any core. The main secondary objectives were the number of men who could avoid biopsy after nonsuspicious mpMRI, the number of biopsy cores taken, and oncologic follow-up. Differences in proportions were tested using McNemar’s test with adjusted Wald confidence intervals for differences of proportions with matched pairs.
Results and limitations
The MRI pathway detected csPCa in 159/626 (25%) patients and insignificant prostate cancer (insignPCa) in 88/626 patients (14%). TRUSGB detected csPCa in 146/626 patients (23%) and insignPCa in 155/626 patients (25%). Relative sensitivity of the MRI pathway versus the TRUSGB pathway was 1.09 for csPCa (p = 0.17) and 0.57 for insignPCa (p < 0.0001). The total number of biopsy cores reduced from 7512 to 849 (–89%). The MRI pathway enabled biopsy avoidance in 309/626 (49%) patients due to nonsuspicious mpMRI. Immediate TRUSGB detected csPCa in only 3% (10/309) of these patients, increasing to 4% (13/309) with 1-yr follow-up. At the same time, TRUSGB would overdetect insignPCa in 20% (63/309). “Focal saturation” by four additional perilesional cores to MRGB improved the detection of csPCa in 21/317 (7%) patients. Compared with the literature, our proportion of nonsuspicious mpMRI cases is significantly higher (27–36% vs 49%) and that of equivocal cases is lower (15–28% vs 6%). This is probably due to the high-quality standard in this study. Therefore, a limitation is the duplication of these results in less experienced centers.
Conclusions
In biopsy-naïve men, the MRI pathway compared with the TRUSGB pathway results in an identical detection rate of csPCa, with significantly fewer insignPCa cases. In this high-quality standard study, almost half of men have nonsuspicious MRI, which is higher compared with other studies. Not performing TRUS biopsy is at the cost of missing csPCa only in 4%.
Patient summary
We compared magnetic resonance imaging (MRI) with MRI-guided biopsy against standard transrectal ultrasound biopsy for the diagnosis of prostate cancer in biopsy-naïve men. Our results show that patients can benefit from MRI because biopsy may be omitted in half of men, and fewer indolent cancers are detected, without compromising the detection of harmful disease. Men also need fewer needles to make a diagnosis.
In this multicentre Dutch trial, all consecutive patients with an elevated PSA (> 3 ng/ml) were included into a prospective, powered comparative effectiveness study, and underwent a pre-biopsy 3T MRI followed by systematic biopsy and targeted cores in case of abnormal MRI (PIRADS 3-5). All targeted biopsies were performed using the in-bore approach.
The overall detection rate by combining both pathways was 53%, with 30% of significant prostate cancers. When analysing separately the clinically significant PCa rates according to the biopsy scheme, differences between both pathways were minimal in case of PIRADS 5. For PIRADS 3-4 lesions, it reached 12% favouring the MRI pathway. The clinically significant PCa detection rate was 23% after MRI-targeted biopsy compared with 25% after TRUS systematic biopsy. So, no clear superiority of in-bore biopsies compared with TRUS biopsy has been reported in MRI positive patients. Avoiding biopsies in case of normal MRI would decrease by 49% the number of men needed to biopsy and would miss only 3% of significant PCa. If PSA density was used as criterion for biopsy in negative MRI patients, no significant PCa would have been missed when using a cut-off of PSA density at 0.15 ng/ml/gr. During follow-up, 13% of patients with negative MRI underwent repeat biopsies with the diagnosis of 3 significant PCa only. Interestingly, the proportion of men avoiding biopsy was almost twice that reported in PROMIS and PRECISION trials. This may be explained by the low prevalence of significant PCa in a contemporary screening cohort and by the high-quality of MRI standards, in both university and non-university settings.