Diffusion-weighted magnetic resonance imaging: a potential non-invasive marker of tumour aggressiveness in localized prostate cancer

Abstract

Aim: To evaluate diffusion-weighted magnetic resonance imaging (DW-MRI) as a marker for disease aggressiveness by comparing tumour apparent diffusion coefficients (ADCs) between patients with low- versus higher-risk localized prostate cancer. Method: Forty-four consecutive patients classified as low- [n = 26, stageT1/T2a, Gleason score ≤ 6, prostate-specific antigen (PSA) < 10 (group 1)] or intermediate/high- [n = 18, stage ≥ T2b and/or Gleason score ≥ 7, and/or PSA > 10 (group 2)] risk, who subsequently were monitored with active surveillance or started neoadjuvant hormone and radiotherapy, respectively, underwent endorectal MRI. T2-weighted (T2W) and DW images (5 b values, 0-800 s/mm2) were acquired and isotropic ADC maps generated. Regions of interest (ROIs) on T2W axial images [around whole prostate, central gland (CG), and tumour] were transferred to ADC maps. Tumour, CG, and peripheral zone (PZ = whole prostate minus CG and tumour) ADCs (fast component from b = 0-100 s/mm2, slow component from b = 100-800 s/mm2) were compared. Results: T2W-defined tumour volume medians, and quartiles were 1.2 cm3, 0.7 and 3.3 cm3 (group 1); and 6 cm3, 1.3 and 16.5 cm3 (group 2). There were significant differences in both ADCfast (1778 ± 264 × 10-6 versus 1583 ± 283 × 10-6 mm2/s, p = 0.03) and ADCslow (1379 ± 321 × 10-6 versus 1196 ± 158 × 10-6 mm2/s, p = 0.001) between groups. Tumour volume (p = 0.002) and ADCslow (p = 0.005) were significant differentiators of risk group. Conclusion: Significant differences in tumour ADCs exist between patients with low-risk, and those with higher-risk localized prostate cancer. DW-MRI merits further study with respect to clinical outcomes. © 2008 The Royal College of Radiologists.