The Role of Imaging in Suspected Prostate Cancer Realtime Elastography
realtime elastography alone did not allow identification of the prostate cancer index lesion with satisfactory reliability. However, the combination of realtime elastography and data from 12 randomised core biopsies has the potential to correctly identify the prostate cancer index lesion. In a study by Mitterberger et al.,14
Realtime elastography is a promising modality for posterior cancer identification, but it needs to be validated. In a study by Walz et al.,13
Figure 1: Four Cases of Prostate Cancers Identified at Multiparametric 1.5T Magnetic Resonance Imaging and Diagnosed by Targeted Biopsies
T2-W Case 1 DWI T1-W TRUS biopsy
84 patients
with suspected prostate cancer and scheduled for prostate biopsies underwent realtime elastography, TRUS and MRI. The findings of realtime elastography were compared with those of the other examinations and pathological findings. Of the 84 patients, 36 had benign lesions and 48 had prostate cancer. The diagnostic sensitivity, specificity, accuracy, positive predictive value and negative predictive value were 91.7, 72.2, 83.3, 81.5% and 86.7 %, respectively, for realtime elastography and 85.4, 63.9, 76.2, 75.9 and 76.7, respectively, for TRUS (p>0.05). The specificity of realtime elastography (72.2 %) was significantly higher than that of MRI (44.4 %) (p=0.03). The realtime elastography findings were not significantly correlated with the pathological findings and PSA (p>0.05) and the diagnostic sensitivity of realtime elastography decreased along with the enlargement of the prostate. If realtime elastography is to be used as a diagnostic test to supplement clinical diagnosis of cancer, it has to be validated using detailed examination of radical prostatectomy specimens as a reference standard.
Contrast-enhanced Colour Doppler Ultrasound Contrast-enhanced colour Doppler ultrasound (CECD-US) necessitates intravenous injection of microbubble US contrast agent. Mitterberger et al. reported significant benefit of CECD-US targeted biopsy compared with systematic biopsies.14
hypervascular areas in the PZ and compared with systematic biopsies. Cancer was detected in 559 (31 %) of 1,776 patients; in 476 (27 %) of the 1,776 patients, it was detected with CECD-US and in 410 (23 %), it was detected with systematic biopsies (p<0.001). The detection rate for CECD-US targeted biopsy cores (10.8 % or 961 of 8,880 cores) was significantly better than for systematic biopsy cores (5.1 % or 910 of 17,760 cores, p<0.001). Among patients with a positive biopsy for prostate cancer, cancer was detected by CECD-US alone in 149 patients (27 %) and by systematic biopsies alone in 83 (15 %) (p<0.001). Again, the diagnosis of anterior tumours with radical prostatectomy specimens as a reference standard was not studied. In a study by Taverna et al., 300 patients with suspected prostate cancer were randomised to have TRUS-guided systematic biopsies with or without targeted biopsies to suspicious areas on CECD-US imaging.15
Low
sensitivity, specificity and accuracy of CECD-US were found with no significant difference for cancer detection rate between groups.
Multiparametric Magnetic Resonance Imaging Multiparametric MRI (mp-MRI) of the prostate obtained prior to biopsy in patients with suspected prostate cancer was shown to be effective in both anterior and posterior zones of the gland2,16,17
(see Figure 1). In
an extended series and using radical prostatectomy histopathology as a reference standard test, the sensitivity and specificity of mp-MRI for identifying significant cancer foci (i.e., with tumour volume>0.5 cm3) in clinically localised disease (including anterior prostate cancers) were 86 and 94 %, respectively.2
The negative predictive value was
95 %. Mean cancer volume detected at MRI was 2.44 ml (range 0.02–14.5) and mean cancer volume not detected at MRI was 0.16 ml (range 0.01–2.4). However, the use and diffusion of mp-MRI requires a
EUROPEAN UROLOGICAL REVIEW
Targeting Biopsies to a Suspicious Area Targeting biopsies to an MRI-suspicious area was proven to be very effective in improving detection of anteriorly located cancers, which represent 20 % of the largest cancers in unselected patients suspected to have prostate cancer, beyond the area sampled by posterior biopsies.2,18
This was true whether tissue biopsy was performed under MRI-directed realtime biopsy (MRI guidance)19 with MRI ‘cognitive’ co-registration.18
or under TRUS guidance Also, the sensitivity of biopsy for 125 T2-W Case 2 DWI T1-W early T1-W late
T2-W Case 3
DWI
T1-W
TRUS biopsy
T2-W Case 4
DWI
T1-W early
T1-W late
Targeted biopsies were performed in
Axial T2-weighted (T2-W), diffusion-weighted (DW), T1-weighted double contrast enhanced (T1-W DCE) and axial transrectal ultrasonography (TRUS) images. Visual reading of all sequences allows suspicion scoring and location determination. Suspicious areas on magnetic resonance imaging are shown by the lilac arrows. Case 1: Cancer located in the peripheral zone (PZ) at midline with 7 mm hyposignal area (T2-W), low apparent diffusion coefficient (ADC) (DW) and intense early enhancement (T1-W DCE), with a suspicion score of 5; TRUS showed a hypoechoic corresponding area; prostate specific antigen (PSA) was 7.9 ng/ml; maximal cancer length was 6 mm at targeted biopsies Gleason score 4+4; systematic biopsies were negative. Case 2: Cancer located in the left lobe of the PZ with 10 mm hyposignal area (T2-W), low ADC (DW) and intense early enhancement (T1-W DCE), with a suspicion score of 5; TRUS showed a hypoechoic corresponding area; PSA was 6.9 ng/ml; maximal cancer length was 6 mm at targeted biopsies Gleason score 4+4; systematic biopsies were negative. Case 3: Cancer located in right antero-lateral horn of the PZ with 19 mm hyposignal area (T2-W), low ADC (DW) and weak enhancement (T1-W DCE), with a suspicion score of 4; TRUS showed an equivocal hypoechoic corresponding area; PSA was 7.8 ng/ml; maximal cancer length was 4 mm at targeted biopsies Gleason score 3+4; systematic biopsies were negative. Case 4: Anterior prostate cancer located in the anterior fibromuscularstroma anterior to the right transition zone (TZ) at apex with 13 mm hyposignal area (T2-W), low ADC (DW) and intense early enhancement (T1-W DCE), with a suspicion score of 5; TRUS showed an equivocal hypoechoic corresponding area; maximal cancer length was 7 mm at targeted biopsies; systematic biopsies were negative.
degree of discipline in its conduct, reporting and evaluation. A recent European MRI Consensus Panel16
recommended that this modern
imaging modality needs to be delivered in a quality-controlled manner with uniformly high standards and used as a test prior to biopsy. T2-weighted, dynamic contrast-enhanced and diffusion-weighted MRI were the key sequences incorporated into the minimum requirements but spectroscopy was not recommended. A five-point scale was agreed upon for specifying the probability of malignancy, with a minimum of 16–27 prostatic sectors of analysis to include a pictorial representation of suspicious foci (see Figure 2).
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