Diffusion weighted and dynamic contrast enhanced MRI as an imaging biomarker for stereotactic ablative body radiotherapy (SABR) of primary renal cell carcinoma

PLoS One. 2018 Aug 16;13(8):e0202387. doi: 10.1371/journal.pone.0202387. eCollection 2018.

Abstract

Purpose: To explore the utility of diffusion and perfusion changes in primary renal cell carcinoma (RCC) after stereotactic ablative body radiotherapy (SABR) as an early biomarker of treatment response, using diffusion weighted (DWI) and dynamic contrast enhanced (DCE) MRI.

Methods: Patients enrolled in a prospective pilot clinical trial received SABR for primary RCC, and had DWI and DCE MRI scheduled at baseline, 14 days and 70 days after SABR. Tumours <5cm diameter received a single fraction of 26 Gy and larger tumours received three fractions of 14 Gy. Apparent diffusion coefficient (ADC) maps were computed from DWI data and parametric and pharmacokinetic maps were fitted to the DCE data. Tumour volumes were contoured and statistics extracted. Spearman's rank correlation coefficients were computed between MRI parameter changes versus the percentage tumour volume change from CT at 6, 12 and 24 months and the last follow-up relative to baseline CT.

Results: Twelve patients were eligible for DWI analysis, and a subset of ten patients for DCE MRI analysis. DCE MRI from the second follow-up MRI scan showed correlations between the change in percentage voxels with washout contrast enhancement behaviour and the change in tumour volume (ρ = 0.84, p = 0.004 at 12 month CT, ρ = 0.81, p = 0.02 at 24 month CT, and ρ = 0.89, p = 0.001 at last follow-up CT). The change in mean initial rate of enhancement and mean Ktrans at the second follow-up MRI scan were positively correlated with percent tumour volume change at the 12 month CT onwards (ρ = 0.65, p = 0.05 and ρ = 0.66, p = 0.04 at 12 month CT respectively). Changes in ADC kurtosis from histogram analysis at the first follow-up MRI scan also showed positive correlations with the percentage tumour volume change (ρ = 0.66, p = 0.02 at 12 month CT, ρ = 0.69, p = 0.02 at last follow-up CT), but these results are possibly confounded by inflammation.

Conclusion: DWI and DCE MRI parameters show potential as early response biomarkers after SABR for primary RCC. Further prospective validation using larger patient cohorts is warranted.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Carcinoma, Renal Cell / diagnostic imaging*
  • Carcinoma, Renal Cell / radiotherapy*
  • Contrast Media / analysis
  • Diffusion Magnetic Resonance Imaging / methods*
  • Female
  • Follow-Up Studies
  • Humans
  • Kidney / diagnostic imaging
  • Kidney / radiation effects
  • Kidney Neoplasms / diagnostic imaging*
  • Kidney Neoplasms / radiotherapy*
  • Male
  • Radiosurgery / methods*

Substances

  • Contrast Media

Grants and funding

This study was supported by a Contributing to Australia Scholarship and Science (CASS) Science and Medicine grant SM/11/3784 to SS (http://www.cassfoundation.org/) and a Ferring Pharmaceutical Fellowship Award from the Royal Australia and New Zealand College of Radiation Oncology (https://www.ranzcr.com/). Image Analysis Group provided support in the form of a salary for author Diana Roettger. The funders had no additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.