Diffusion-weighted MRI treatment monitoring of primary hypofractionated proton and carbon ion prostate cancer irradiation using raster scan technique

J Magn Reson Imaging. 2017 Sep;46(3):850-860. doi: 10.1002/jmri.25635. Epub 2017 Feb 2.

Abstract

Purpose: To investigate parametric changes in the apparent diffusion coefficient (ADC) at multiple timepoints during and after completion of primary proton and carbon ion irradiation of prostate cancer (PCa) as compared with normal-appearing prostate parenchyma.

Materials and methods: In all, 92 patients with histologically confirmed PCa received either proton or carbon ion hypofractionated radiotherapy (RT). All were prospectively evaluated with diffusion-weighted magnetic resonance imaging (DWI-MRI) at five timepoints: baseline, day 10 during therapy and 6 weeks, 6 months, and 18 months after treatment. Linear mixed models (LMM) were used to evaluate the effects of radiation, antihormonal therapy, time, and type of particle irradiation on manual ADC measurements. ADC differences related to prostate-specific antigen (PSA) relapse according to PSA thresholds and to Vancouver rules and Phoenix criteria were examined using LMM and unpaired Student's t-test.

Results: A measurable and continuous increase of tumor ADC measurements from baseline (1.194 × 10-3 mm2 /s) during (1.350 × 10-3 mm2 /s, day 10, P = 0.006) and after treatment (1.355/1.430/1.490 × 10-3 mm2 /s, week 6 / month 6 / month 18, P = 0.001/<0.001/<0.001) was found. ADC values of normal-appearing control tissue remained unchanged. Androgen deprivation (P ≥ 0.320), different PSA thresholds (P = 0.634), and PSA relapse criteria according to Vancouver rules (P ≥ 0.776) had no effect. A weak association between 18-month measurements and Phoenix criteria (P = 0.046) was found.

Conclusion: ADC parametric changes were distinct in tumor tissue, highlighting the ability of diffusion MRI to evaluate different aspects of the microscopic pathophysiology. Although promising, their use as noninvasive imaging biomarkers requires further validation.

Level of evidence: 1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:850-860.

Keywords: apparent diffusion coefficient; carbon ion irradiation; diffusion-weighted imaging; prostate cancer; prostate specific antigen; proton irradiation; radiation therapy.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Carbon
  • Diffusion Magnetic Resonance Imaging / methods*
  • Follow-Up Studies
  • Humans
  • Image Processing, Computer-Assisted / methods*
  • Male
  • Middle Aged
  • Prostate / diagnostic imaging
  • Prostate / radiation effects
  • Prostatic Neoplasms / diagnostic imaging*
  • Prostatic Neoplasms / radiotherapy*
  • Protons
  • Retrospective Studies
  • Treatment Outcome

Substances

  • Protons
  • Carbon