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

Purpose 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. Materials and Methods We retrospectively analyzed 68 treatment-na & iuml;ve 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. Results 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%).Conclusion Segmentation of PV is a time-intensive task. Inter-reader variability can impact PSAd-based diagnosis of PCa. Automated prostate segmentation methods are welcome.