Giovanni Barchetti1, Martina Pecoraro1, Isabella Ceravolo1, Maurizio Del Monte1, Carlo Catalano1, and Valeria Panebianco1
1Department of Radiology, Sapienza University, Policlinico Umberto I, Rome, Italy
Synopsis
To stratify
patients with PI-RADSv2 category 3 to define the correct diagnostic work-up (biopsy or follow-up), quantitatively analyzing mpMRI parameters (ADC,
k-trans, K-ep and ve). Among 1272 men who underwent mpMRI, we retrospectively enrolled
98 patients treated with radical prostatectomy. Furthermore, we selected 100
negative patients. The 198 mpMRI exams were randomly, blindly reviewed by two
radiologists. 95 PI-RADSv2 category 3 were found and quantitatively analyzed.
ROC and AUC were determined to identify a cut-off value to define which PI-RADS
3 lesion should be biopsied. Quantitative imaging represents a tool to
objectively stratify patients classified as PI-RADSv2 category 3.
Introduction
Multiparametric MRI of the prostate (mpMRI) has become
the state-of-the-art technique for staging and characterizing prostate cancer
(PCa). Nowadays, European recommendation rely on qualitative analysis of mpMRI
images applying PI-RADSv2 scoring system;1,2 however there is a
consistent number of patients that fall in the equivocal group of PI-RADSv2
category 3 in which other clinical factors become increasingly important.2 Currently, much of
the work is focusing on evaluation of mpMRI parameters’ quantitative analysis that
has
got the advantage of offering user-independent data, to determine its clinical
applications. In light of the background, the aim of the study is to stratify patients with
PI-RADSv2 category 3 which might undergo TRUS-MRI targeted biopsy,
quantitatively analyzing mpMRI parameters (ADC, k-trans, K-ep and ve).Methods
Among
the 1272 men who underwent mpMRI for PCa suspicion at our centre from January
2015 to September 2017, we retrospectively enrolled 98 patients who were subsequently treated with radical prostatectomy. Furthermore, we selected 100 patients
suspected of harboring PCa with at least two negative mpMRI examination (nMRI),
the second 8-12 months apart from the first, at least one negative systematic
transrectal ultrasound guided prostate biopsy after nMRI, and a minimum
follow-up of 60 months. Every exam was performed at 3T mpMRI using the same
protocol, which included T2-weighted imaging, diffusion weighted imaging (DWI)
with apparent diffusion coefficient (ADC) maps and dynamic contrast-enhanced
imaging (DCE). The mpMRI exams of the final population of 198 patients
were randomly reviewed in consensus by two radiologists with more than 10
years’ experience in the field. The readers were blinded to both clinical data
and histopathology reports, when available. For all patients, a structured
report was obtained, and each lesion was described according to PI-RADSv2. A
total of 95 PI-RADSv2 category 3 were found and quantitative analysis of these regions was performed. The quantitative evaluation was performed using GenIQ
software for measuring pharmacokinetic parameters (k-trans, k-ep and ve) from
DCE perfusion study, and READY View (GE Healthcare) for ADC values calculated
from DWI sequences.Results
The
median patients age was 62, the median total PSA was 6,32 ng/mL, the median PSA
density was 0,12 ng/mL2. Mean ADC value of 79,785 mm2/s
(95% CI = 75,427 to 84,143), mean k-trans of 0,273 min-1 (95% CI= 0,229
to 0,316), mean k-ep of 0,532 min-1 (95% CI = 0,462 to 0, 623) and mean
ve of 0,71 (95% CI = 0,236 to 0, 317). Receiver operating characteristic
analysis and area under curve (AUC) were determined to identify a cut-off value
to define which PI-RADS 3 lesion should be biopsied by TRUS-MRI targeted
biopsy. Accordingly, we stratified results in two subgroups: group A, patients
enter follow-up programs; group B, patients suited to undergo TRUS-MRI targeted
biopsy. Discussion
The
major limitation of PI-RADS score system version 2 is how to define the
clinical approach to patients classified as PI-RADS category 3. Indeed, for
PI-RADS 3 other clinical factors
become increasingly important such as PSA density. 2 Nonetheless, few
studies in literature have demonstrated how quantitative analysis of mpMRI
parameters might give further objective data to standardize the diagnostic
work-up of PI-RADS 3 patients. Felker et al 3 reported how the
yield of targeted biopsy in PI-RADSv2 category 3 TZ lesions for clinically
significant PCa significantly improves to 60% among men with PSA density of
0.15 ng/mL2 or greater and lesion ADC value of less than 1000 mm2/s. Metzger et
al 4 reported that among
others ADC
values, K-trans, and k-ep were significantly different between cancer and
noncancer voxels (P , .001), with ADC showing the best accuracy. Hoang Dinh et al 5 described how the
model of the 10th percentile of the ADC with time-to-peak (TTP) yielded accurate results in
discriminating cancers with a Gleason score of at least 7 among peripheral zone (PZ) lesions. Hauth
et al 6 reported how ADC min can differentiate PCa from benign prostate lesions
in PZ. Peak enhancement might be able to differentiate low grade from
high-grade PCa. We demonstrated that by quantitatively measuring
mpMRI parameters of PI-RADS 3 lesion, confirmed by histopathologic correlation,
it is possible to differentiate patients’ that should undergo to TRUS-MRI
targeted biopsy from those who should enter follow-up programs.Conclusion
Quantitative
analysis of multiparametric MRI parameters might represent a tool to
objectively stratify the equivocal group of patients classified as PI-RADSv2
category 3, to define the correct patients’ diagnostic planning (biopsy or
follow-up). Hence, to improve prostate cancer detection while decreasing the number
of unnecessary biopsies and the number of false negative results.Acknowledgements
No acknowledgement found.References
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