Prostate Cancer Screening with PSA and MRI Followed by Targeted Biopsy Only.

BACKGROUND: Screening for prostate cancer is burdened by a high rate of overdiagnosis. The most appropriate algorithm for population-based screening is unknown. METHODS: We invited 37,887 men who were 50 to 60 years of age to undergo regular prostate-specific antigen (PSA) screening. Participants with a PSA level of 3 ng per milliliter or higher underwent magnetic resonance imaging (MRI) of the prostate; one third of the participants were randomly assigned to a reference group that underwent systematic biopsy as well as targeted biopsy of suspicious lesions shown on MRI. The remaining participants were assigned to the experimental group and underwent MRI-targeted biopsy only. The primary outcome was clinically insignificant prostate cancer, defined as a Gleason score of 3+3. The secondary outcome was clinically significant prostate cancer, defined as a Gleason score of at least 3+4. Safety was also assessed. RESULTS: Of the men who were invited to undergo screening, 17,980 (47%) participated in the trial. A total of 66 of the 11,986 participants in the experimental group (0.6%) received a diagnosis of clinically insignificant prostate cancer, as compared with 72 of 5994 participants (1.2%) in the reference group, a difference of -0.7 percentage points (95% confidence interval [CI], -1.0 to -0.4; relative risk, 0.46; 95% CI, 0.33 to 0.64; P<0.001). The relative risk of clinically significant prostate cancer in the experimental group as compared with the reference group was 0.81 (95% CI, 0.60 to 1.1). Clinically significant cancer that was detected only by systematic biopsy was diagnosed in 10 participants in the reference group; all cases were of intermediate risk and involved mainly low-volume disease that was managed with active surveillance. Serious adverse events were rare (<0.1%) in the two groups. CONCLUSIONS: The avoidance of systematic biopsy in favor of MRI-directed targeted biopsy for screening and early detection in persons with elevated PSA levels reduced the risk of overdiagnosis by half at the cost of delaying detection of intermediate-risk tumors in a small proportion of patients. (Funded by Karin and Christer Johansson's Foundation and others; GÖTEBORG-2 ISRCTN Registry number, ISRCTN94604465.).

Manual prostate MRI segmentation by readers with different experience: a study of the learning progress.

OBJECTIVE: To evaluate the learning progress of less experienced readers in prostate MRI segmentation. MATERIALS AND METHODS: One hundred bi-parametric prostate MRI scans were retrospectively selected from the Göteborg Prostate Cancer Screening 2 Trial (single center). Nine readers with varying degrees of segmentation experience were involved: one expert radiologist, two experienced radiology residents, two inexperienced radiology residents, and four novices. The task was to segment the whole prostate gland. The expert's segmentations were used as reference. For all other readers except three novices, the 100 MRI scans were divided into five rounds (cases 1-10, 11-25, 26-50, 51-76, 76-100). Three novices segmented only 50 cases (three rounds). After each round, a one-on-one feedback session between the expert and the reader was held, with feedback on systematic errors and potential improvements for the next round. Dice similarity coefficient (DSC) > 0.8 was considered accurate. RESULTS: Using DSC > 0.8 as the threshold, the novices had a total of 194 accurate segmentations out of 250 (77.6%). The residents had a total of 397/400 (99.2%) accurate segmentations. In round 1, the novices had 19/40 (47.5%) accurate segmentations, in round 2 41/60 (68.3%), and in round 3 84/100 (84.0%) indicating learning progress. CONCLUSIONS: Radiology residents, regardless of prior experience, showed high segmentation accuracy. Novices showed larger interindividual variation and lower segmentation accuracy than radiology residents. To prepare datasets for artificial intelligence (AI) development, employing radiology residents seems safe and provides a good balance between cost-effectiveness and segmentation accuracy. Employing novices should only be considered on an individual basis. CLINICAL RELEVANCE STATEMENT: Employing radiology residents for prostate MRI segmentation seems safe and can potentially reduce the workload of expert radiologists. Employing novices should only be considered on an individual basis. KEY POINTS: • Using less experienced readers for prostate MRI segmentation is cost-effective but may reduce quality. • Radiology residents provided high accuracy segmentations while novices showed large inter-reader variability. • To prepare datasets for AI development, employing radiology residents seems safe and might provide a good balance between cost-effectiveness and segmentation accuracy while novices should only be employed on an individual basis.

Prostate Cancer Diffusion-Weighted Magnetic Resonance Imaging: Does the Choice of Diffusion-Weighting Level Matter?

BACKGROUND: Diffusion-weighted magnetic resonance imaging plays an important role in multiparametric assessment of prostate lesions. The derived apparent diffusion coefficient (ADC) could be a useful quantitative biomarker for malignant growth, but lacks acceptance because of low reproducibility. PURPOSE: To investigate the impact of the choice of diffusion-weighting levels (b-values) on contrast-to-noise ratio and quantitative measures in prostate diffusion-weighted MRI. STUDY TYPE: Retrospective and simulation based on published data. SUBJECTS: Patient cohort (21 men with Prostate Imaging-Reporting and Data System (PI-RADS) version 2 score ≥3) from a single-center study. FIELD STRENGTH/SEQUENCE: 3 T/diffusion-weighted imaging with single-shot echo-planar imaging. ASSESSMENT: Both clinical data and simulations based on previously acquired data were used to quantify the influence of b-value choice in normal peripheral zone (PZ) and PZ tumor lesions. For clinical data, ADC was determined for different combinations of b-values. Contrast-to-noise ratio and quantitative diffusion measures were simulated for a wide range of b-values. STATISTICAL TESTS: Tissue ADC and the lesion-to-normal tissue ADC ratios of different b-value combinations were compared with paired two-tailed Student's t-tests. A P-value <0.05 was considered statistically significant. RESULTS: Findings about b-value dependence derived from clinical data and from simulations agreed with each other. Provided measurement was limited to two b-values, simulation-derived optimal b-value choices coincided with PI-RADSv2 recommendations. For two-point measurements, ADC decreased by 15% when the maximum b-value increased from 1000 to 1500 seconds/mm2 , but corresponding lesion-to-normal tissue ADC ratio showed no significant change (P = 0.86 for acquired data). Simulations with three or more measurement points produced ADCs that declined by only 8% over this range of maximum b-value. Corresponding ADC ratios declined between 2.6% (three points) and 3.8% (21 points). Simulations also revealed an ADC reduction of about 19% with the shorter echo and diffusion time evaluated. DATA CONCLUSION: The comprehensive assessment of b-value dependence permits better formulation of protocol and analysis recommendations for obtaining reproducible results in prostate cancer diffusion-weighted MRI. LEVEL OF EVIDENCE: 4 TECHNICAL EFFICACY: Stage 2.

Bi- or multiparametric MRI in a sequential screening program for prostate cancer with PSA followed by MRI? Results from the Göteborg prostate cancer screening 2 trial.

OBJECTIVES: The PIRADS Steering Committee has called for "higher quality data before making evidence-based recommendations on MRI without contrast enhancement as an initial diagnostic work up," however, recognizing biparametric (bp) MRI as a reasonable option in a low-risk setting such as screening. With bpMRI, more men can undergo MRI at a lower cost and they can be spared the invasiveness of intravenous access. The aim of this study was to assess cancer detection in bpMRI vs mpMRI in sequential screening for prostate cancer (PCa). METHODS: Within the ongoing Göteborg PCa screening 2 trial, we assessed cancer detection in 551 consecutive participants undergoing prostate MRI. In the same session, readers first assessed bpMRI and then mpMRI. Four targeted biopsies were performed for lesions scored PIRADS 3-5 with bpMRI and/or mpMRI. RESULTS: Cancer was detected in 84/551 cases (15.2%; 95% CI: 12.4-18.4) with mpMRI and in 83/551 cases (15.1%; 95% CI: 12.3-18.2%) with bpMRI. The relative risk (RR) for cancer detection with bpMRI compared to mpMRI was 0.99 (95% one-sided CI: > 94.8); bpMRI was non-inferior to mpMRI (10% non-inferiority margin). bpMRI resulted in fewer false positives, 45/128 (35.2%), compared to mpMRI, 52/136 (38.2%), RR = 0.92; 95% CI: 0.84-0.98. Of 8 lesions scored positive only with mpMRI, 7 were false positives. The PPV for MRI and targeted biopsy was 83/128 (64.8%) for bpMRI and 84/136 (61.8%) for mpMRI, RR = 1.05, 95% CI: 1.01-1.10. CONCLUSIONS: In a PSA-screened population, bpMRI was non-inferior to mpMRI for cancer detection and resulted in fewer false positives. KEY POINTS: • In screening for prostate cancer with PSA followed by MRI, biparametric MRI allows radiologists to detect an almost similar number of prostate cancers and score fewer false positive lesions compared to multiparametric MRI. • In a screening program, high sensitivity should be weighed against cost and risks for healthy men; a large number of men can be saved the exposure of gadolinium contrast medium by adopting biparametric MRI and at the same time allowing for a higher turnover in the MRI room.

[Prostate cancer - diagnostics and screening]. / Prostatacancer ­ utredning, klinisk diagnostik och screening.

Prostate-specific antigen (PSA) based screening is controversial, even though randomised trials show that screening can reduce prostate cancer mortality. The main reason is that screening leads to overdiagnosis of indolent cancers that would never have surfaced clinically in the absence of screening. Recently, several large studies have shown that magnetic resonance imaging (MRI) improves prostate cancer diagnostics. With MRI, up to half of all men with elevated PSA values can be spared a biopsy. When a biopsy is needed, the needles can be directed towards the suspicious area in the prostate, which increases the detection of clinically significant tumors. In Sweden, regional programmes with organised prostate cancer testing were introduced in 2020. These programmes aim to make prostate cancer testing more standardized, efficient, and equitable. In the future, biomarkers and AI-based systems will likely be important to further improve prostate cancer diagnostics.

Prostate Cancers in the Prostate-specific Antigen Interval of 1.8-3 ng/ml: Results from the Göteborg-2 Prostate Cancer Screening Trial.

BACKGROUND: Magnetic resonance imaging (MRI) and targeted biopsies reduce overdiagnosis of prostate cancer (PC). It is uncertain how this strategy performs for low prostate-specific antigen (PSA) levels. OBJECTIVE: To investigate the Prostate Imaging Reporting and Data System (PI-RADS) distribution, frequency, and characteristics of screen-detected PC with PSA of 1.8-<3 ng/ml and 3-<10 ng/ml. DESIGN, SETTING, AND PARTICIPANTS: In the population-based Göteborg-2 screening study, 17974 men choose to participate by having a PSA test (2015-2020). One-third of the participants (n = 6006) were randomized to arm 3, men with a PSA value of ≥1.8 ng/ml were recommended for MRI. Men with positive MRI (PI-RADS 3-5) had four targeted biopsies from each MRI-visible lesion. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Clinically significant PC was defined as Gleason score ≥3 + 4. RESULTS AND LIMITATIONS: A total of 6006 men were included. The median age was 55.9 yr (interquartile range [IQR] 52.6-59.6). Of them, 4929 (82%) had PSA of <1.8 ng/ml, 670 (11%) had PSA of 1.8-<3 ng/ml (low-PSA group, median PSA 2.1 ng/ml [IQR 1.9-2.5]), and 377 (6.3%) had PSA of 3-<10 ng/ml (high-PSA group, median PSA 3.9 ng/ml [IQR 3.3-5.0]). PI-RADS scores of 3, 4, and 5 were observed in 7.8%, 15%, and 1.0% of men in the low-PSA group, and in 6.9%, 17%, and 5.3% of men in the high-PSA group, respectively. PC was found in 64 men (41%, 95% confidence interval [CI] 0.33-0.49) with positive MRI findings in the low-PSA group, of whom 33 (21%) had Gleason 6 (insignificant PC) and 31 (20%) had Gleason ≥7 (significant PC). In the high-PSA group, PC was detected in 61 men (56%, 95% CI 0.46-0.66), of whom 26 (24%) had Gleason 6 (insignificant PC) and 35 (32%) had Gleason ≥7 (significant PC). Limitations include results from only a single screening round. CONCLUSIONS: A non-negligible number of men with PSA 1.8-3 ng/ml have clinically significant PC. Whether a delay in the diagnosis of these tumors until they reached PSA ≥3 ng/ml would impair their chance of cure remains to be evaluated. PATIENT SUMMARY: We studied screening using prostate-specific antigen (PSA) and magnetic resonance imaging in men with PSA 1.8-3 ng/ml. We found a non-negligible number of potentially harmful prostate cancers in these men.

Performance of 4Kscore as a Reflex Test to Prostate-specific Antigen in the GÖTEBORG-2 Prostate Cancer Screening Trial.

BACKGROUND AND OBJECTIVE: We investigated whether adding 4Kscore as a reflex test to prostate-specific antigen (PSA) could improve the screening algorithm for prostate cancer (PC). METHODS: In the GÖTEBORG-2 PC screening trial, 38 000men (50-60 yr) were invited to PSA testing and, if elevated, followed by magnetic resonance imaging (MRI). For 571 men with PSA ≥3.0 ng/ml and evaluable outcomes, 4Kscore was calculated. The performance using a prespecified 4Kscore cutoff of 7.5% was evaluated. KEY FINDINGS AND LIMITATIONS: The area under the curve for 4Kscore to identify intermediate- and high-risk PC was 0.84 (95% confidence interval 0.79-0.89), and the positive predictive value, and negative predictive value were 15% (0.12-0.20) and 99% (97-100%), respectively. Of the 54 men diagnosed with intermediate- or high-grade PC, two had a 4Kscore cutoff below 7.5%, both with organ-confined intermediate-risk PC. Per 1000 men with elevated PSA, adding 4Kscore would have resulted in avoidance of MRI for 408 (41%) men, biopsies for 95 (28% reduction) men, and diagnosis of 23 low-grade cancers (23% reduction) while delaying the diagnosis of four men with intermediate-grade cancers (4%). CONCLUSIONS AND CLINICAL IMPLICATIONS: Including 4Kscore as a reflex test for men with elevated PSA reduces the need for MRI and biopsy markedly, and results in less overdiagnosis of low-grade PC at the cost of delaying the diagnosis of intermediate-grade PC in a few men. These results add further evidence for including new blood-based biomarkers in addition to PSA to improve the harm and benefit ratio of PC screening and reduce the need for resource-demanding MRI and biopsies. PATIENT SUMMARY: In this study, 4Kscore, a blood-based biomarker, as a reflex test for men with elevated prostate-specific antigen (PSA), reduces the need for magnetic resonance imaging and biopsy. These results support the inclusion of new blood-based biomarkers in addition to PSA.

Population-based Organised Prostate Cancer Testing: Results from the First Invitation of 50-year-old Men.

BACKGROUND: The European Union recently recommended evaluation of the feasibility of organised prostate cancer screening. In Sweden, regional population-based organised prostate cancer testing (OPT) programmes were introduced in 2020. OBJECTIVE: To describe initial participation rates and diagnostic outcomes. DESIGN, SETTING, AND PARTICIPANTS: The three most populated Swedish regions invited all men aged 50 yr to OPT by a letter in 2020-2022. Men with prostate-specific antigen (PSA) ≥3 ng/ml were referred for prostate magnetic resonance imaging (MRI). PSA assays differed across regions. Men with Prostate Imaging Reporting and Data System (PI-RADS) 1-3 and PSA density ≥0.15 ng/ml/cm3 or PI-RADS 4-5 were referred for a biopsy. Data were obtained from the Swedish Register for Organised Prostate Cancer Testing. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Overall and regional participation rates, PSA distributions, PI-RADS score distributions, cancer detection, and treatment were evaluated. RESULTS AND LIMITATIONS: A total of 23 855 (35%) of 68 060 invited men participated; 696 (2.9%) had PSA ≥3 ng/ml, and of them, 306 (44%) had a biopsy indication and 221 (32%) had a biopsy. On biopsy, 93 (42%) had Gleason grade group ≥2 (0.39% of PSA-tested men) and 44 (20%) Gleason grade group 1 cancer. Most men with cancer had treatment with curative intent (70%) or were under active surveillance (28%). Across regions, proportions of men with PSA ≥3 ng/ml ranged from 2.3% to 4.0%, and those with PI-RADS score 4-5 ranged from 12% to 21%. A limitation is that results are applicable only to first testing of men in their early 50s. CONCLUSIONS: The OPT programmes are feasible with good compliance to the diagnostic pathway. The use of MRI and PSA density avoided a biopsy for over half of the men with PSA ≥3 ng/ml. Inter-regional differences in diagnostic outcomes show a need for standardisation of the diagnostic pathway's components. PATIENT SUMMARY: We report the diagnostic outcomes of inviting 68 000 50-yr-old men to organised prostate cancer testing.

Men's Acceptance of Screening for Prostate Cancer with Prostate-specific Antigen, Magnetic Resonance Imaging, and Prostate Biopsy.

BACKGROUND: A prerequisite before introducing a screening program is that the screening examinations are acceptable to participants. OBJECTIVE: To evaluate the acceptance and bother of prostate cancer screening examinations. DESIGN, SETTING, AND PARTICIPANTS: The randomized population-based GÖTEBORG-2 prostate cancer screening trial invited >37 000 men for prostate-specific antigen (PSA) testing followed by magnetic resonance imaging (MRI) in case of elevated PSA and prostate biopsy (targeted and/or systematic) if indicated. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Participants were asked to fill out a questionnaire and rate the level of bother associated with each examination (PSA, MRI, and prostate biopsy) on a categorical scale ranging from 1 to 5 (1 = "not at all bothersome" and 5 = "very bothersome"), and to rate their willingness to repeat the examinations, by marking an X on a continuous scale ranging from 0 to 10 (0 = "yes, without any hesitation" and 10 = "no, absolutely not"). Wilcoxon signed rank test was used. RESULTS AND LIMITATIONS: Compliance with MRI was 96% (1790/1872), compliance with biopsy was 89% (810/907), and the response rate to the questionnaire was 75% (608/810). Men who underwent all examinations (n = 577) responded that biopsy was more bothersome than PSA test (p < 0.001) and MRI (p < 0.001). High levels of bother (≥4 out of 5) were reported by 2% (12/577) for PSA test, 8% (46/577) for MRI, and 43% (247/577) for biopsy. Men were more willing to repeat MRI than biopsy (p < 0.001), but the difference was small (median 0.2 [interquartile range 0.1-0.6] vs 0.5 [0.1-2.0]). CONCLUSIONS: Biopsies are more bothersome than MRI, but a large majority of men accept to repeat both examinations if necessary. Omitting biopsy for MRI-negative men and shifting to targeted biopsies only will reduce bother for men participating in prostate cancer screening. PATIENT SUMMARY: We asked men how bothersome they found the prostate-specific antigen (PSA) test, magnetic resonance imaging (MRI), and prostate biopsies. Biopsies were more bothersome than PSA and MRI, but most men were willing to repeat all procedures if necessary.

Designing and Implementing a Population-based Organised Prostate Cancer Testing Programme.

BACKGROUND: European guidelines recommend that well-informed men at elevated risk of having prostate cancer (PCa) should be offered prostate-specific antigen (PSA) testing with risk-stratified follow-up. The Swedish National Board of Health and Welfare recommends against screening for PCa but supports regional implementation of organised prostate cancer testing (OPT). OBJECTIVE: To report the process for designing and implementing OPT programmes. DESIGN, SETTING, AND PARTICIPANTS: Population-based OPT programmes in two Swedish regions, designed to include men aged between 50 and 74 yr, launched in September 2020 for 50-yr-old men. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: The number of men invited, the participation rate, and the numbers of magnetic resonance imaging (MRI) scans, urological visits, and biopsies from September 2020 to June 2021 were recorded. RESULTS AND LIMITATIONS: Two Swedish regions co-designed an OPT programme with a risk-stratified diagnostic algorithm based on prostate-specific antigen (PSA), PSA density, MRI findings, and age. An automated administrative system was developed on a nationwide web-based platform. Invitation letters and test results are automatically generated and sent out by post. Men with PSA ≥3ng/ml, a suspicious MRI lesion, and/or PSA density ≥0.15 ng/ml/cm3 are referred for a prostate biopsy. Test results are registered for quality control and research. By June 2021, a total of 16 515 men were invited, of whom 6309 (38%) participated; 147 had an MRI scan and 39 underwent prostate biopsy. The OPT framework, algorithm, and diagnostic pathways have been working well. CONCLUSIONS: We designed and implemented a framework for OPT with a high grade of automation. The framework and organisational experiences may be of value for others who plan a programme for early detection of PCa. PATIENT SUMMARY: We describe the implementation of an organised testing programme for early detection of prostate cancer in two Swedish regions. This model is the first of its kind and may serve as a template for similar programmes.

Prostate Cancer Screening with Magnetic Resonance Imaging: Results from the Second Round of the Göteborg Prostate Cancer Screening 2 Trial.

BACKGROUND: The Göteborg 2 prostate cancer (PC) screening (G2) trial evaluates screening with prostate-specific antigen (PSA) followed by magnetic resonance imaging (MRI) in case of elevated PSA levels. OBJECTIVE: To assess the safety of using a 2-yr interval in men who were previously screened positive with PSA but had negative MRI or positive MRI with a negative biopsy. DESIGN, SETTING, AND PARTICIPANTS: A total of 61 201 men aged 50-60 yr were randomized and 38 366 were invited for screening (years 2015-2020). Men with positive MRI (Prostate Imaging Reporting and Data System [PI-RADS] score ≥3) were scheduled for targeted biopsies. Men with negative MRI or negative biopsies were reinvited after 2 yr. Round 1 and 2 MRI scans (PI-RADS ≥3) of men not diagnosed with PC in round 1 were re-read and classified according to Prostate Cancer Radiological Estimation of Change in Sequential Evaluation (PRECISE) by two radiologists. Interval PCs (detected outside the program before invitation to round 2) were identified by linking to the Regional PC Registry. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Tabulation of overall detection of PC was done. RESULTS AND LIMITATIONS: Between October 2017 and June 2020, 474 men with round 1 elevated PSA and MRI underwent a second screening. Of those, 19% had nonelevated PSA in round 2 and were not examined further. Of the remaining 376 men, 89% had negative MRI. Targeted biopsies yielded 14 PCs: nine grade group (GG) 1 and five GG 2-3. In men with PI-RADS ≥3 and PC diagnosed in round 2, only two (GG 1) progressed according to the PRECISE criteria and the remainder were stable. Ten interval PCs were diagnosed: seven GG 1, one GG 2, and two GG 5. The two GG 5 PCs were PI-RADS 4 and 5 with negative round 1 biopsy. CONCLUSIONS: A 2-yr interval seems to be safe in men with negative MRI, while men with PI-RADS 4 and 5 lesions with negative biopsies should have a closer follow-up. PATIENT SUMMARY: In prostate cancer screening, a 2-yr follow-up seems to be safe if magnetic resonance imaging did not show highly suspicious findings.

The GÖTEBORG prostate cancer screening 2 trial: a prospective, randomised, population-based prostate cancer screening trial with prostate-specific antigen testing followed by magnetic resonance imaging of the prostate.

OBJECTIVE: To describe the study design of the GÖTEBORG prostate cancer screening (PC) 2 (Göteborg-2), a prospective, randomised, population-based trial of PC screening. This trial evaluates whether prostate-specific antigen (PSA) testing followed by 3 Tesla prostate magnetic resonance imaging (MRI) and targeted biopsy can reduce overdiagnosis, while maintaining the detection of clinically significant cancer, compared to PSA-screening and systematic biopsy. MATERIALS AND METHODS: A random sample of men 50-60 years in the Göteborg area, Sweden, identified from the Total Population Register, were randomised to either a screening or control group (CG). Participants in the screening group (SG) were further randomised into one of three arms: (1) PSA-test; if PSA ≥ 3 ng/mL, then MRI and systematic biopsy, plus targeted biopsy to suspicious lesions as per Prostate Imaging - Reporting and Data System, version 2 (PI-RADSv2) 3-5; (2) PSA-test; if PSA ≥ 3 ng/mL, then MRI, and targeted biopsy only if PI-RADSv2 3-5; (3) identical to Arm 2, except lower PSA-cut-off ≥1.8 ng/mL. The primary outcome is the detection rate of clinically insignificant PC (defined as Gleason Score 3 + 3 [Grade Group 1]) comparing all men with PSA ≥ 3 ng/mL in Arm 1 vs. Arm 2 + 3. RESULTS: Randomisation and enrolment started in September 2015. Accrual has hitherto resulted in 38,770 men randomised to the SG. The participation rate is 50%. Invitation to the first screening round was completed in June 2020. CONCLUSIONS: The Göteborg-2 trial will provide new knowledge about the performance of prostate MRI in a screening setting.

Performance and inter-observer variability of prostate MRI (PI-RADS version 2) outside high-volume centres.

Objective: Despite the growing trend to embrace pre-biopsy MRI in the diagnostic pathway for prostate cancer (PC), its performance and inter-observer variability outside high-volume centres remains unknown. This study aims to evaluate sensitivity of and variability between readers of prostate MRI outside specialized units with radical prostatectomy (RP) specimen as the reference standard.Materials and methods: Retrospective study comprising a consecutive cohort of all 97 men who underwent MRI and subsequent RP between January 2012 and December 2014 at a private hospital in Sweden. Three readers, blinded to clinical data, reviewed all images (including 11 extra prostate MRI to reduce bias). A tumour was considered detected if the overall PI-RADS v2 score was 3-5 and there was an approximate match (same or neighbouring sector) of tumour sector according to a 24 sector system used for both MRI and whole mount sections.Results: Detection rate for the index tumour ranged from 67 to 76%, if PI-RADS 3-5 lesions were considered positive and 54-66% if only PI-RADS score 4-5 tumours were included. Detection rate for aggressive tumours (GS ≥ 4 + 3) was higher; 83.1% for PI-RADS 3-5 and 79.2% for PI-RADS 4-5. The agreement between readers showed average [Formula: see text] values of 0.41 for PI-RADS score 3-5 and 0.51 for PI-RADS score 4-5.Conclusions: Prostate MRI evidenced a moderate detection rate for clinically significant PC with a rather large variability between readers. Clinics outside specialized units must have knowledge of their performance of prostate MRI before considering omitting biopsies in men with negative MRI.