Prostate Cancer
Table 1: Summary of Reported Focal Therapy Trials Modality Number Therapy
Bahn et al., Cryotherapy 31 200633
Ellis et al., 200734
Lambert
et al., 200735 Onik et al., 200830–32
Cryotherapy 60 Cryotherapy 25 Cryotherapy 120
COLD Registry, Cryotherapy 795 200937
Truesdale et al., 201036
Muto et al., HIFU 200840
Berret et al., HIFU
200949 Ahmed et al., HIFU
201141 Lindner et al., FLA 200946
29 12 20 12
Bilateral PZ TRUS + ipsilateral TZ
Not specified TRUS 5.4 7.3 Hemiablation Template 7.3 Focal/partial TRUS ≤10
No cut off specified ≤7
≤7 ≤6 Cryotherapy 77 Hemiablation TRUS Hemiablation TRUS Hemiablation TRUS + Doppler 7.2 6 Focal/partial Template 8.3 Focal/partial TRUS Hemiablation TRUS 6.5
No cut off 70.6 % 3.6 % specified ≤7
70.8 % 0 %
No cut off 85 % 0 % specified ≤9
≤8
Biopsy Mean PSA GS 4.95
≤7
Potency Incontinence Disease Control 89 %
0 %
96 % (biopsy) 92 % (ASTRO) 76.6%
88 % (biopsy)
84 % (PSA nadir <50 %) 28 93 %
65 % 2.8 % 0 %
81–83 % (ASTRO) 35–68 % (Phoenix) 87 % (biopsy)
72.7 % (Phoenix) 76.5 %
0 % 95 % 5 % 100 % 0 % 58.0 % 89 % 50 %
ASTRO = American Society for Therapeutic Radiology and Oncology; FLA = focal laser ablation; GS = Gleason score; HIFU = high-intensity focused ultrasound; m = months; PSA = prostate-specific antigen; PZ = peripheral zone; TRUS = trans-rectal ultrasound; TZ = transition zone.
from 32–99 %.18
These authors note that the wide range in performance within the literature likely reflects differences between studies in equipment, study cohorts and methodology used for pathological correlation. However, it has been noted that MRI has improved sensitivity for lesions of a greater size, as evidenced by Puech et al. who compared pre-biopsy MRI performance with RP specimens. This study found that the sensitivity of combined T2WI and DCE improved from 32 % for detection of cancer foci of any volume to 86 % for cancer foci >0.5 ml.21
In terms of specificity, MRI is challenged
because a variety of benign processes including post-biopsy haemorrhage, prostatitis and benign prostate hyperplasia (BPH) all may mimic cancer on T2WI.
While inclusion of a functional technique within a prostate MRI protocol improves performance, even greater diagnostic performance is achieved when these functional techniques are applied in combination. Turkbey et al. showed that the predictive value of combined T2WI, DCE and MRS was greater than that of any combination of two of these three techniques.19
In addition, Riches et
al. investigated the use of DCE-MRI, MRS and DWI and observed that the combination of any two of these functional techniques improved cancer detection compared with the use of any single parameter alone.23
86
Functional MRI techniques measure additional properties of prostate tissue (i.e. vascularity in DCE-MRI, metabolism in MRS and cellularity in DW-MRI) that are not reflected by anatomical T2WI. As noted previously, each of these techniques provides distinct additional information that has been shown to improve the detection of prostate tumours when combined with T2WI. For instance, Futterer et al. performed T2WI, DCE and MRS in 34 patients before prostatectomy.22 These authors report an area under the curve (AUC) for tumour detection of 0.68 using T2WI alone, compared with 0.80 and 0.91 for T2WI combined with MRS and T2WI combined with DCE, respectively. Haider et al. performed T2WI and DWI before prostatectomy in 49 patients and reported an AUC for peripheral zone tumour detection of 0.81 using T2WI alone, compared with 0.89 for combined T2WI and DWI.20
MRI has been shown to add incremental value to traditional pre-operative staging nomograms of prostate cancer.24
43.2 12 24 34 120 12 6
Follow-up (m) 70
15.2
In one study,
Augustin et al. compared the predictive ability of 3 T MRI and Partin nomograms in men who underwent prostatectomy and found that MRI was more accurate in the prediction of extracapsular extension.25 In addition, Turkbey et al. demonstrated a significant negative correlation between apparent diffusion coefficient (ADC) values obtained from DWI with both GS and D’Amico clinical risk score.26 Rastinehad et al. found that the degree of suspicion of prostatic lesions on MpMRI utilising all three functional techniques significantly correlates with D’Amico risk stratification.27
Collectively, these studies
suggest that, once optimised, MRI will play a role not only in tumour detection, but also staging and assessment of risk of disease.
Further studies are necessary to compare the results of tumour detection in saturation biopsies versus MRI targeted biopsies alone.
The ability to reliably identify prostate lesions on MRI may be the key to finding a reliable alternative to saturation biopsy for accurate staging and mapping of prostate tumours. It is currently possible to biopsy abnormal MRI findings that are suspicious for tumour under direct MRI guidance. Roethke et al. reported that in performing MRI guided biopsy of suspicious findings in 100 patients with at least one prior negative trans-rectal ultrasound (TRUS) biopsy, cancer was detected in 52 patients.28
Limitations to the use of MpMRI in focal therapy candidate selection at this time include its relatively high cost, a lack of standardisation of imaging protocols and high inter-observer variability in image interpretation and reporting. Overall, however, MpMRI shows promise for providing an accurate non-invasive method for tumour detection and identification of candidates for focal therapy.
Focal Therapies
A variety of focal treatment modalities are currently undergoing trials (see Table 1). Given the novelty of the concept of focal therapy for prostate cancer, no consensus currently exists with regards to the optimal ablative approach (i.e. method, amount of tissue to be ablated),
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