An Evaluation of Screening Pathways Using a Combination of Magnetic Resonance Imaging and Prostate-specific Antigen: Results from the IP1-PROSTAGRAM Study

Abstract

Background: The use of prostate-specific antigen (PSA) testing to screen for prostate cancer has been fraught with under- and overdiagnosis. Short, noncontrast magnetic resonance imaging (MRI) might detect more grade group ≥2 cancers with similar rates of biopsy.

Objective: To evaluate strategies that combined PSA and MRI to select men based in the community for a prostate biopsy.

Design, setting, and participants: IP1-PROSTAGRAM was a prospective, population-based, paired cohort study of 408 men aged 50-69 yr conducted at seven UK primary care practice and two imaging centres (from October 10, 2018 to May 15, 2019).

Intervention: All participants underwent screening with a PSA test, MRI (T2-weighted and diffusion), and transrectal ultrasound (b-mode and elastography). If any test was screen positive, a systematic 12-core biopsy was performed. Additional image-fusion targeted biopsies were taken if the MRI or ultrasound was positive.

Outcome measurements and statistical analysis: We conducted an analysis, set out in the statistical plan a priori, comparing 13 different pathways including PSA-alone, MRI-alone, and a range of PSA thresholds and MRI scores. The performance of each pathway was evaluated focusing on the trade-offs between biopsy referral rates and detection of grade group ≥2 cancers. A targeted biopsy was performed only where the PROSTAGRAM MRI showed a lesion score of 3, 4, or 5.

Results and limitations: The standard PSA pathway (PSA ≥3 ng/ml + systematic biopsy) would lead to 10% of men being referred for a biopsy and a 1.0% detection rate of grade group ≥2 cancers. Pathways that relied on MRI alone set at a threshold score of 3 for a biopsy led to higher biopsy rates, but with benefit of high cancer detection rates. The pathway that combined an initial low PSA threshold (≥1.0 ng/ml) and MRI score ≥4 accurately identified a high rate of grade group ≥2 cancers (2.5%, 95% confidence interval 1.3-4.6) while recommending fewer patients for a biopsy (7.1%, 95% confidence interval 4.9-10.2). The results are pertinent to only one screening round, the impact of repeat screening rounds is not evaluated, and the required MRI capacity is currently lacking.

Conclusions: Our results highlight the trade-off that exists between reducing excessive numbers of biopsies and maintaining grade group ≥2 cancer detection rates. A pathway that combines PSA ≥1 ng/ml and MRI score ≥4 maintains the detection of grade group ≥2 cancers while recommending fewer men for biopsies and would be the preferred strategy to evaluate in future studies at the first screening round.

Patient summary: The IP1-PROSTAGRAM study shows that PROSTAGRAM magnetic resonance imaging in men with a prostate-specific antigen level of ≥1.0 ng/ml could be a promising pathway to evaluate in future screening trials.

Keywords: Fast magnetic resonance imaging; PROSTAGRAM; Prostate biopsy; Prostate cancer; Screening.