Variability of segmented prostate volume on MRI: impact on PSA density for prostate cancer diagnosis

PSA density (PSAd), based on prostate volume (PV), is a decision-making parameter for prostate cancer (PCa) diagnosis and risk stratification. We assessed variability in prostate manual segmentation on MRI and its impact on PV and PSAd.We retrospectively analyzed 68 treatment-naïve patients, aged 66.2±6.9 years, with increased PSA and/or positive digital endorectal examination who underwent MRI, with available biopsy/follow-up. Three radiologists (R1, R2, R3) manually segmented the gland on T2-weighted images slice-by-slice. Dice similarity coefficient (DSC), Welch's t-test, and 95% confidence intervals (CIs) were used.Of 68 patients with a PSA of 7.59±4.80 ng/mL, 38 had biopsy-confirmed PCa, and the remaining 30 were negative on biopsy/follow-up. The segmentation time per patient ranged from 4 to 7 min. Pairs R1-R2, R1-R3, and R2-R3 showed a different number of segmented slices (p<0.001) and PV (p<0.001). DSC for prostate gland segmentation ranged from 0.871 to 0.890. An outlier (prostatitis with PSA 35 ng/mL) was excluded from PSA/PSAd analysis. Based on segmentation by R1, the PSA was 7.37±3.70 ng/mL and PSAd was 0.124±0.070 ng/mL/mL in the 38 patients with PCa, while these values were 6.91±2.79 ng/mL and 0.111±0.062 ng/mL/mL, respectively, in the 29 patients without PCa. Using the threshold of ≥0.15 ng/mL/mL, variations in segmented PV impacted PSAd-based classification, resulting in 1 false negative for R1 and another false negative for R2 (false-negative rate for both 1/38, 2.63%, 95% CI 0.10-13.8%).Segmentation of PV is a time-intensive task. Inter-reader variability can impact PSAd-based diagnosis of PCa. Automated prostate segmentation methods are welcome. · Manual prostate segmentation is a time-consuming task performed in clinical practice. · Inter-reader variability of PV segmentation was low, with high DSC values. · Minor PV differences led to false-negative PSAd classification in 2.63% cases.. · Colarieti A, Venturi A, Cressoni M et al. Variability of segmented prostate volume on MRI: impact on PSA density for prostate cancer diagnosis. Rofo 2025; DOI 10.1055/a-2624-7634.