Objectives: To demonstrate the feasibility of an 8Gy focal radiation boost to a dominant intraprostatic lesion (DIL), identified using multiparametric MRI (mpMRI) and assess the potential outcome compared with a uniform 74Gy prostate dose.
Methods: The DIL location was predicted in 23 patients using a histopathologically-verified model combining diffusion-weighted imaging (DWI), dynamic contrast-enhanced imaging (DCE-MRI), T2-maps and 3D magnetic resonance spectroscopic imaging (MRSI). The DIL defined prior to neo-adjuvant hormone-downregulation was registered to MRI acquired post-hormone therapy and subsequently to CT radiotherapy scans. Intensity modulated radiotherapy treatment (IMRT) was planned for an 8Gy focal boost with 74Gy dose to the remaining prostate. Areas under the dose-volume histograms (DVH) for prostate, bladder and rectum, the tumour control probability (TCP) and normal tissue complication probabilities (NTCP) were compared with the uniform 74Gy IMRT plan.
Results: Deliverable IMRT plans were feasible for all patients with identifiable DILs (20/23). Areas under the DVHs were increased for the prostate (75.1±0.6 vs. 72.7±0.3Gy, p< 0.001) and decreased for rectum (38.2±2.5 vs. 43.5±2.5Gy, p< 0.001) and bladder (29.1±9.0 vs. 36.9±9.3Gy, p< 0.001) for the boosted plan. The prostate TCP was increased (80.1±1.3 vs. 75.3±0.9Gy, p< 0.001) and rectal NTCP lowered (3.84±3.65 vs. 9.70±5.68Gy, p=0.04) in the boosted plan. The bladder NTCP was negligible for both plans.
Conclusions: Delivery of a focal boost to an mpMRI-defined DIL is feasible and significant increases in TCP and therapeutic ratio were found. Advances in knowledge: Delivery of a focal boost to an mpMRI-defined DIL demonstrates statistically significant increases in TCP and therapeutic ratio.
Written by:
Riches SF, Payne GS, Desouza NM, Dearnaley D, Morgan VA, Morgan SC, Partridge M. Are you the author?
CRUK & EPSRC Cancer Imaging Centre, Royal Marsden NHS Foundation Trust and Institute of Cancer Research, Sutton, Surrey, UK.
Reference: Br J Radiol. 2014 Mar 6:20130813.
doi: 10.1259/bjr.20130813
PubMed Abstract
PMID: 24601648
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