Is apparent diffusion coefficient associated with clinical risk scores for prostate cancers that are visible on 3-T MR images?

Abstract

Purpose: To investigate whether apparent diffusion coefficients (ADCs) derived from diffusion-weighted (DW) magnetic resonance (MR) imaging at 3 T correlate with the clinical risk of prostate cancer in patients with tumors that are visible on MR images, with MR imaging/transrectal ultrasonography (US) fusion-guided biopsy as a reference.

Materials and methods: Forty-eight consecutive patients (median age, 60 years; median serum prostate-specific antigen value, 6.3 ng/mL) who underwent DW imaging during 3-T MR imaging with an endorectal coil were included in this retrospective institutional review board-approved study, and informed consent was obtained from each patient. Patients underwent targeted MR imaging/transrectal US fusion-guided prostate biopsy. Mean ADCs of cancerous target tumors were correlated with Gleason and D'Amico clinical risk scores. The true risk group rate and predictive value of the mean ADC for classifying a tumor by its D'Amico clinical risk score was determined by using linear discriminant and receiver operating characteristic analyses.

Results: A significant negative correlation was found between mean ADCs of tumors in the peripheral zone and their Gleason scores (P = .003; Spearman ρ = -0.60) and D'Amico clinical risk scores (P < .0001; Spearman ρ = -0.69). ADC was found to distinguish tumors in the peripheral zone with intermediate to high clinical risk from those with low clinical risk with a correct classification rate of 0.73.

Conclusion: There is a significant negative correlation between ADCs and Gleason and D'Amico clinical risk scores. ADCs may therefore be useful in predicting the aggressiveness of prostate cancer.

Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.10100667/-/DC1.

Figure 1a:

Screen captures of the DW MR imaging tool used for analysis. (a) Region of interest (red) in a tumor in the right peripheral zone (PZ) with a Gleason score of 4+4 has a mean ADC of (670.5 ± 103.1) × 10⁻⁶ mm²/sec, whereas (b) that in a tumor in the anterior left of the prostate with a Gleason score of 3+3 has a mean ADC of (1505 ± 212.4) × 10⁻⁶ mm²/sec.

Figure 1b:

Screen captures of the DW MR imaging tool used for analysis. (a) Region of interest (red) in a tumor in the right peripheral zone (PZ) with a Gleason score of 4+4 has a mean ADC of (670.5 ± 103.1) × 10⁻⁶ mm²/sec, whereas (b) that in a tumor in the anterior left of the prostate with a Gleason score of 3+3 has a mean ADC of (1505 ± 212.4) × 10⁻⁶ mm²/sec.

Figure 2a:

Box and whisker plots of ADCs for tumors with different Gleason scores in (a) whole prostate and (b) PZ only. Center line = median, top of box = 75th percentile, bottom of box = 25th percentile, whiskers = data within 1.5 interquartile ranges, ○ = outliers, ∗ = significant difference (P < .001) between ADCs for different Gleason scores (a: Spearman ρ = −0.55; b: Spearman ρ = −0.60).

Figure 2b:

Box and whisker plots of ADCs for tumors with different Gleason scores in (a) whole prostate and (b) PZ only. Center line = median, top of box = 75th percentile, bottom of box = 25th percentile, whiskers = data within 1.5 interquartile ranges, ○ = outliers, ∗ = significant difference (P < .001) between ADCs for different Gleason scores (a: Spearman ρ = −0.55; b: Spearman ρ = −0.60).

Figure 3a:

Box and whisker plots of ADCs for tumors with different D’Amico clinical risk scores in (a) whole prostate and (b) PZ only. Center line = median, top of box = 75th percentile, bottom of box = 25th percentile, whiskers = data within 1.5 interquartile ranges, ○ = outliers, ∗ = significant difference (P < .0001) between ADCs for different D’Amico clinical risk scores (a: Spearman ρ = −0.64; b: Spearman ρ = −0.69).

Figure 3b:

Box and whisker plots of ADCs for tumors with different D’Amico clinical risk scores in (a) whole prostate and (b) PZ only. Center line = median, top of box = 75th percentile, bottom of box = 25th percentile, whiskers = data within 1.5 interquartile ranges, ○ = outliers, ∗ = significant difference (P < .0001) between ADCs for different D’Amico clinical risk scores (a: Spearman ρ = −0.64; b: Spearman ρ = −0.69).

Figure 4:

True risk group rate (Sensitivity) of different threshold ADCs for determining low versus intermediate to high (Intermediate-High) D’Amico clinical risk scores in all tumors (PZ+CG) and tumors only in the PZ.