WORKSHOPS 4–6 : Tuesday 17 October 2006, 16:00–17:30

The objectives of this presentation are to discuss the clinical role of magnetic resonance (MR) in local and nodal staging of prostate cancer, and to show new developments. The clinical questions are how can we improve with new MR imaging (MRI) techniques: localization, local staging, targeted radiotherapy planning, and nodal staging? Accurate tumour localisation is important for detection of prostate cancer in patients with clinical suspicion (e.g. elevated prostate-specific antigen (PSA)) and a negative trans-rectal ultrasound biopsy. When combining anatomical (T2-weighted) high resolution techniques by applying either 1.5 T with an endorectal coil, or 3 T without an endorectal coil, with contrast enhanced dynamic MRI and MR spectroscopy, localization accuracy is ∼90%. The additional use of this technique has been shown to increase the rate of positive biopsies. In addition, when the tumour is accurately localised, local staging by inexperienced radiologists improves. These localisation techniques allow targeted radiotherapy planning (e.g. by giving 90 Gy to the dominant intraprostatic lesion), as fusion with these ‘functional’ MR images and computed tomography (CT) is feasible. Local staging at 1.5 T without using an endorectal coil results in a sensitivity of 64% and a specificity of 72%. When using an endorectal coil, specificity can improve to 98% with equal sensitivity. Advanced MRI at 3 T using an endorectal coil has resulted in a sensitivity of 88% and a specificity of 96%. When a high specificity reading is performed in patients with intermediate to high risk for extracapsular disease (PSA > 10 or Gleason > 6 or T3 at digital rectal examination (DRE)), and if prostatectomy is not performed in a stage T3 on such an MRI, the use of MRI results in a cost-saving of 2500 euros per patient. As current cross sectional imaging techniques and positron emission tomography (PET)-CT have limited sensitivity in detecting nodal metastases (CT 35%, and [18F]FDG-PET 65%), in patients with intermediate to high risk for nodal metastases (PSA > 10 or Gleason > 6 or T3 at DRE) routinely a pelvic lymph node dissection is performed. However, it has been showed that with this (obturator) dissection not all positive nodes are detected. The combination of a new MRI (lymph node specific) contrast agent (MRL) has been shown to have a sensitivity and specificity >90% and a negative predictive value of 97% in detecting even small nodes. In patients with a negative MRL a diagnostic pelvic lymph node dissection can be safely avoided. This results in a cost saving of approximately 2000 euros per patient.