Optimized use of MRI in a PSA based prostate cancer screening program

Abstract: The overall aim of this thesis was to optimize different aspects of the use of MRI in screening for prostate cancer. Paper 1 was based on preoperative MRI in a prostatectomy cohort. Papers 2-4 were based on data from the ongoing Göteborg Prostate Cancer Screening 2 Trial, a randomized, population-based, long-term trial assessing screening with PSA followed by MRI in men aged 50-61 years in Gothenburg and surrounding municipalities. Biopsies were used as the reference standard. In Paper 1 three non-expert readers retrospectively assigned PI-RADSv2 scores in MRI performed at multiple sites. A fair to moderate reader agreement (k-score 0.41) and slightly lower tumor detection (overall 70%) compared to previous reports highlights the importance of a quality assurance program. In Paper 2 cancer detection with bpMRI was compared with mpMRI in a prospective, paired diagnostic study. Bi-parametric MRI was non-inferior to mpMRI and should be considered the method of choice as it also reduces room turn over time and saves healthy men exposure of gadolinium contrast agents. In Paper 3 a retrospective analysis of men with peripheral zone PI-RADS 3 lesions was performed. Multivariable regression models were built to assess contrast enhancement, lesion size and, PSA density (PSAD) as predictors of cancer. Only PSAD was strongly correlated to cancer. Selecting men for biopsy based on PSAD could potentially help significantly reduce the number of biopsies but data was not sufficient to establish a clinically reliable threshold. In Paper 4 PRECISE scores were retrospectively assigned in a 2- year MRI follow-up of men with first-round negative MRI or positive MRI with negative biopsies. Few men were diagnosed with cancer in the second round and most MRI lesions were of stable appearance. This provides important safety data in support of a follow-up interval of at least 2 years.

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