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Imaging modalities in prostate cancer Bahjat moussa PGY4 urology Dr Georges Assaf Moderator 24-04-14 PET in PC patients • Role of functional imaging – not well established yet • The aim of this review – to offer an overview about the main applications of choline PET in PC patients Detection of intra-prostatic cancer • Use of choline PET/CT for initial diagnosis and local staging of prostate cancer – not recommended as a first line screening method • The only potential application of PET/CT – increase the detection rate of cancer on repeated TRUS-guided biopsies – in patients in which at least 2 inconclusive TRUSguided biopsy have been already performed Staging • The use of choline PET/CT for preoperative LN staging – showed very contradictory results – However good specificity and PPV – limited to patients with very high risk for LN positive status according to nomograms • At the present time – routine clinical use of choline PET/CT cannot be recommended in staging patients with PC • A negative Choline PET/CT – is not sufficient to rule out a lymph-adenectomy • PET could be useful to exclude from surgery – patients with high surgical risk in which the presence of LN lesions were assessed by PET (high PPV) • PET/CT showed – sensitivity 60% – a much better specificity 97% Restaging • Imaging should be able to find the site of recurrence – distinguish between local failure and distant metastasis Detection of LN and distant recurrence in PC patients with biochemical recurrence – significantly high detection rate – relationship between detection rate and Trigger PSA values – a relationship between detection rate and PSA kinetics • a crucial role as first diagnostic procedure in patients who demonstrate a fast growing PSA kinetics and low Trigger PSA • In case of slow growing PSA kinetics – sensitivity of PET does not seems to be so high – questionable if a PET/CT should be performed as first imaging procedure • In case of local relapse – TRUS and/or pelvic endorectal MR remain the first procedures – choline PET/CT could have only a complementary role to exclude the presence of distant metastasis, before a local RT salvage treatment Conclusion • Use of choline PET/CT for initial diagnosis and staging – is not recommended as a first-line method • Most important application of choline PET/CT – restaging of the disease in case of biochemical relapse for the detection of LN and distant recurrence Conclusion • Choline PET/CT – could play a crucial role as first diagnostic procedure in PC patients who show a fast growing PSA kinetics • The diagnostic evidence is stronger in restaging than in staging settings • Proper patient selection – PSA level – PSA doubling time – initial tumor stage is the key to avoiding FN results up front • The use of choline PET/CT scanning – May accurately provide the localisation of the site of prostate recurrence in a single step • Choline PET/CT’s detection rate of recurrences rises together with the increase in PSA serum value • According to the current available data – the routine use of choline PET/CT scanning cannot be commonly recommended for PSA values <1 ng/ml • Independent predictors of positive choline PET/CT – PSA DT – previous biochemical failure – locally advanced tumour – pathologic lymph node disease at initial staging • Can choline positron emission tomography/computed tomography help individualise treatment decisions? • Confirmatory data are still needed • Choline PET/CT imaging has recently been proposed to allow new opportunities for individualised treatment on recurrent lesions after radical treatment for PCa • Patients with local recurrence after RP – best treated by salvage RT when the PSA serum level is <0.5 ng/ml • Choline PET/CT scanning is not commonly useful in this scenario – low detection rate for PSA serum values <1 ng/ml • Choline PET/CT scanning, providing wholebody information on Pca spread – may be useful in selecting patients to be referred to local treatment – by distinguishing those patients with local recurrences from those who present with distant metastases Salvage lymphadenectomy • Choline PET/CT scanning – very useful for indicating the presence of lymph nodal involvement • in patients who present with a progressive PSA increase after radical treatment • it provides a basis for further treatment decisions Role of MRI According to the guidelines PSA increase over a threshold of 0.2 ng/ml later than 6 to 12 months after radical prostatectomy • suggests treatment failure with a high risk of local recurrence increase within a shorter period • correlates with distant metastasis For EBRT; biochemical failure • increasing PSA level after a nadir level Transrectal ultrasound-guided biopsy • The current reference standard for the detection of local recurrence in patients with biochemical failure • Invasive • may fail to depict some tumours because only a small fraction of the gland is sampled Computed tomography • Not widely used for the detection of local recurrence – low accuracy in the differentiation of local recurrence from postsurgical scarring MRI • MRI can accurately detect local recurrences after EBRT and radical prostatectomy – DCE MRI is particularly accurate • The addition of 1H-MRSI to DCE MRI – significantly improve the diagnostic accuracy of local prostate cancer recurrence MRI – usually used for local staging in intermediate and high risk patient groups – useful in low risk patients as well – sensitivity and specificity 75% and 95% respectively • Functional MRI techniques – diffusion-weighted magnetic resonance (DW-MR) – dynamic contrast-enhanced (DCE-MR) – MR spectroscopy • Conventional MRI – only able to diagnose metastatic lymph nodes bigger than 10 mm • A newly invented MRI technique lymphotropic superparamagnetic nanoparticles – detect occult lymph node metastasis smaller than 10 mm – 100% sensitivity and 95.7% specificity MR Spectroscopy • Measures the level of specific metabolites in the prostate gland – Combination of choline and creatine is measured in MRS – The other metabolite that MRS measures is citrate • accumulate in peripheral zone • high in normal prostate tissue but decreases in malignant tissues MR Spectroscopy • The ratio of Cho+Cr/Ci – used for evaluation of prostate cancer • Higher ratio – in favor of higher risk of malignancy – more than 0.75 is considered as significant and is consistent with prostate cancer MR Spectroscopy • More accurate in detecting prostate cancers with high grade of malignancy – in low grade cancers its accuracy is limited Dynamic Contrast Study • Works based on neo angiogenesis in tumor cells • Angiogenesis rate is high – newly made vessels have low integrity in their wall – more permeable than normal vessels Dynamic Contrast Study • Gadolinium contrast agent is injected – then serial 3D T1- weighted images are obtained • Fast leakage of contrast agent from leaky tumoral vasculature – early enhancement of tumoral tissue in T1 weighted MRI – early wash out of contrast agent are seen in prostate cancer Diffusion Weighted Imaging • Works based on water molecules movements – Water molecules movement decrease in a high cellular environment – so diffusion become lower • Sensitivity and specificity of DWI when added to T2-Weighted MRI for detecting prostate cancer is about 84% and 87% respectively MRI Ability to Detection Bony Metastasis • The most sensitive and specific technique in detecting bony metastasis Whole-body DW imaging • The most newly MRI technique • Very helpful in detection of prostate cancer and its metastasis as well as post cancer therapy fallow up Local Staging of Prostate Cancer • High resolution MR images – especially with the use of endorectal coil – can show with high accuracy • whether the tumor is confined to prostate gland or there is extra capsular extension • The gold standard approach for: – Diagnosis – Staging and management of prostate cancer Is using 1.5 T MR machines with both endorectal and pelvic phased-array coils Evaluation of Local Recurrence After Treatment • MR spectroscopy detects recurrence after radical prostatectomy – 84% and 88% sensitivity and specificity respectively • DWMRI – capable to detect cancer recurrence after radical prostatectomy in patients that conventional MRI has missed recurrence • DW-MR imaging alone shows low sensitivity in cancer recurrence detection after radiotherapy (25%) • In combination with T2-Weighted MRI – sensitivity increases to 62% – Specificity in both condition is acceptable (92% vs 97%) High resolution Multiparametric MR imaging • includes: – regular T1 weighted and T2 weighted images – dynamic contrast-enhanced MRI – diffusion weighted imaging – MR spectroscopy High resolution Multiparametric MR imaging • Obtained in 1.5 T MR machines with simultaneous use of pelvic and endorectal coils – best imaging modality in prostate cancer • useful for – detection and local staging of prostate cancer – follow-up of patients after radical prostatectomy or radiation therapy – detection of skeletal metastasis – targeting biopsies in patients highly suspicious of prostate cancer but with previous negative TRUS guided biopsies References