Role of Magnetic Resonance Imaging in Prostate Cancer Screening: A Pilot Study Within the Göteborg Randomised Screening Trial

Abstract

Background: Magnetic resonance imaging (MRI) and targeted biopsies (TB) have shown potential to more accurately detect significant prostate cancer compared with prostate-specific antigen (PSA) and systematic biopsies (SB).

Objective: To compare sequential screening (PSA+MRI) with conventional PSA screening.

Design, setting, and participants: Of 384 attendees in the 10th screening round of the Göteborg randomised screening trial, 124 men, median age 69.5 yr, had a PSA of ≥ 1.8 ng/ml and underwent a prebiopsy MRI. Men with suspicious lesions on MRI and/or PSA ≥ 3.0ng/ml were referred for biopsy. SB was performed blinded to MRI results and TB was performed in men with tumour-suspicious findings on MRI. Three screening strategies were compared (PSA ≥ 3.0+SB; PSA ≥ 3.0+MRI+TB and PSA ≥ 1.8+MRI+TB).

Outcome measurements and statistical analysis: Cancer detection rates, sensitivity, and specificity were calculated per screening strategy and compared using McNemar's test.

Results and limitations: In total, 28 cases of prostate cancer were detected, of which 20 were diagnosed in biopsy-naïve men. Both PSA ≥ 3.0+MRI and PSA ≥ 1.8+MRI significantly increased specificity compared with PSA ≥ 3.0+SB (0.92 and 0.79 vs 0.52; p<0.002 for both), while sensitivity was significantly higher for PSA ≥ 1.8+MRI compared with PSA ≥ 3.0+MRI (0.73 vs 0.46, p=0.008). The detection rate of significant cancer was higher with PSA ≥ 1.8+MRI compared with PSA ≥ 3.0+SB (5.9% vs 4.0%), while the detection rate of insignificant cancer was lowered by PSA ≥ 3.0+MRI (0.3% vs 1.2%). The primary limitation of this study is the small sample of men.

Conclusion: A screening strategy with a lowered PSA cut-off followed by TB in MRI-positive men seems to increase the detection of significant cancers while improving specificity. If replicated, these results may contribute to a paradigm shift in future screening.

Patient summary: Major concerns in prostate-specific antigen screening are overdiagnosis and underdiagnosis. We evaluated whether prostate magnetic resonance imaging could improve the balance of benefits to harm in prostate cancer screening screening, and we found a promising potential of using magnetic resonance imaging in addition to prostate-specific antigen.

Keywords: Imaging; MRI; PSA screening; Prostate cancer.

Figure 1

Diagram of the pilot study conducted within the 10^th screening round of the Göteborg randomised screening trial. * PSA = prostate specific antigen, PC = prostate cancer, Pos = positive, Neg = negative, SB = systematic biopsy, TB = targeted biopsy,

Figure 2

Estimated sensitivity and specificity of prostate cancer detection depending on screening strategy (prostate-specific antigen (PSA ≥3 ng/ml followed by systematic biopsy, PSA ≥3.0 ng/ml followed by targeted biopsy, and PSA ≥1.8 ng/ml followed by targeted biopsy). Bars indicate 95% confidence intervals for sensitivity (y-axis) and 1-specificity (x-axis). * PSA = prostate specific antigen, Susp MRI = suspicious magnetic resonance imaging (see ‘Methods’ for details), SB = systematic biopsy, TB = targeted biopsy