Radical prostatectomy (RP) is the primary treatment modality for localized prostate cancer. According to the guidelines of the American Urological Association/American Society for Radiation Oncology, biochemical recurrence (BCR) after radical prostatectomy is defined as a serum prostate-specific antigen (PSA) ≥ 0.2 ng/mL followed by a second confirmatory level. BCR indicates a high risk of progression of PSA2 and implies the presence of either locally recurrent or distant disease. In general, guidelines recommend that physicians offer salvage radiotherapy (SRT) to patients with BCR without evidence of distant metastatic disease.

Over the past 20 years, several studies have investigated the ability of multiparametric magnetic resonance imaging (mpMRI) to detect locally recurrent tumors after RP. 16 Its reported sensitivity and specificity vary, but most range...

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1. Patient Selection
This retrospective observational study was approved by the institutional review board, which waived the requirement for informed consent owing to its retrospective nature. A total of 4632 patients who underwent radical prostatectomy for prostate adenocarcinoma between January 2005 and June 2020 were retrospectively enrolled. Among them, 748 patients with initial baseline PSA levels < 0.2 ng/mL which increased after that over that threshold and followed by a second confirmatory PSA level were identified. Of these, 473 patients underwent mpMRI within one month of the second confirmatory PSA test. The remaining 275 patients who did not undergo MRI were excluded from the study. Of 473 patients with mpMRI, five were excluded due to a lack of contrast-enhanced imaging results (n = 3) and poor image quality (n = 2). A flowchart of the patient...

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1. Clinical and pathological characteristics in the MRI and non-MRI groups
The mean age in the MRI group (n = 468) was 66.2 ± 6.9 years, which was not significantly different from that in the non-MRI group (n = 275, 66.2 ± 6.6, p = 0.993). There was no significant difference in mean preoperative PSA levels (ng/mL) (26.3 ± 108.2 vs. 19.8 ± 28.4, p = 0.343), postoperative nadir PSA levels (ng/mL) (0.0 ± 0.0 vs. 0.0 ± 0.0, p = 0.937), PSA levels at BCR (ng/mL) (1.3 ± 4.6 vs. 1.0 ± 2.6, p = 0.257) and mean time (days) to BCR from radical prostatectomy (1042.7 ± 820.5 vs. 1100.4 ± 865.3, p = 0.371), respectively.

Gleason scores of 7 (62.2%) and pT3 (65.0%) were found in most patients in the MRI group, followed by Gleason's score of 9 (27.7%) and pT2 (33.7%). The proportions of other...

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To the best of our knowledge, our study included the largest number of patients (n = 468) with BCR after RP who underwent mpMRI so far. Multiparametric MRI showed low prevalence (7.1%) and sensitivity (27.2%) in our study. In subgroup analysis, different MRI methods did not affect the diagnostic yield.

These results are far lower than those of previous studies that demonstrated the high diagnostic performance of mpMRI. Casciani et al. analyzed DCE-MRI in 51 patients with suspected local recurrence after RP, demonstrating 88% sensitivity and 100% specificity. Panebianco et al. included the highest number of patients (n = 262) with BCR, showing 98–100% sensitivity and 94–97% specificity of combined T2-weighted and DCE-MRI, and 93–94% sensitivity and 89–92% specificity of combined T2-weighted and DWI(b value, 1,000 s/mm2). In a meta-analysis conducted by...

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