Use of CT in radiotherapy planning does not allow us to properly identify the apex of the prostate and the anterior rectal border. CT based prostate volume is 30% larger than on MRI, but only encompasses 84% of the true prostate gland.
MRI has significantly improved identification of prostate gland anatomy, borders and suspicious lesions. Additionally it has reduced rectal toxicity and erectile dysfunction percentages as a result of treatment, the prostate bed volume to be treated and inter-observer delineation. MRI detects postoperative recurrences at a relatively low PSA of 0.5 and above. However, a negative PET-CT or MRI does not rule out local recurrence and should not be used as an excuse to withhold salvage radiotherapy. Recently, incorporation of MRI and PET-CT scans has been shown to have a significant higher overlap with prostate cancer final pathology than both imaging modalities alone.
In conclusion, MRI is mandatory for accurate delineation of the prostate and surrounding organs. It is capable alone, or in combination with PET-CT, to identify intra-prostatic lesions and help significantly reduce the percentages of adverse effects.
Presented by: Dr. Piet Ost, Ghent (BE)
Written by: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto
at the #EAU17 -March 24-28, 2017- London, England