Perfusion-CT monitoring of cryo-ablated renal cells tumors
Journal of Experimental & Clinical Cancer Research
Perfusion-CT monitoring of cryo-ablated renal cells tumors
Ettore Squillaci 1
Guglielmo Manenti 1
Carmelo Cicci 1
Francesca Nucera 1
Pierluigi Bove 0
Giuseppe Vespasiani 0
Laura Russolillo 1
Giovanni Simonetti 1
0 Department of Urology, University Tor Vergata , Rome , Italy
1 Department of Diagnostic and Molecular Imaging, Interventional Radiology and Radiotherapy - University Tor Vergata , Rome , Italy
Background: No single and thoroughly validated imaging method in monitoring of cryoablated renal cell carcinoma (RCC) is available. The purpose of our study was to determine the feasibility of dynamic contrast-enhanced perfusion CT (pCT) in evaluating the hemodynamic response of RCC. Methods: 15 patients (14 male, 1 female; age range, 43-81 years; mean age, 62 years) with cryoablated RCC via a transperitoneal approach, underwent to pCT 6-8 months after cryotherapy. pCT was performed for 65 seconds after intravenous injection of contrast medium (80 mL, 370 mg iodine per millilitre, 4 mL/sec). Perfusion parameters (Time/Density curve; Blood flow, BF; Blood Volume, BV; Mean Transit Time, MTT; Permeability-Surface Area Product, PS) were sampled in the cryoablated tumor area and in ipsilateral renal cortex using deconvolution-based method. A tumor was considered to be not responsive to treatment by CT evidence of pathological contrast enhancement in the cryoablated area or renal mass persistence compared with the preoperative CT control. Written informed consent was obtained from all participants before the study. Results: After cryotherapy, successfully ablated tumor (n = 13) showed decrease in BV (5,39 +/1,28 mL/100 g), BF (69,92 +/- 20,12 mL/100 g/min) and PS (16,66 +/- 5,67 mL/100 g/min) value and increased value of MTT (25,35 +/- 4,3 sec) compared with those of normal renal cortex (BV: 117,86 +/- 31,87 mL/100 g/min; BF: 392,39 +/- 117,32 mL/100 g/min; MTT: 18,02 +/- 3,6 sec; PS: 81,68 +/ - 22,75 mL/100 g/min). In one patient, assessment of perfusion parameters was not feasible for breathing artifacts. One tumor showed poor response to treatment by the evidence of nodular contrast enhancement in the region encompassing the original lesion. Two typical enhancement patterns were obtained comparing the Time-Density curves of responsive and not responsive ablated tumors. Conclusion: Perfusion CT seems to be a feasible and promising technique in monitoring the effects of cryoablation therapy.
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Background
Renal cell carcinoma (RCC) is the most common type of
kidney cancer (8.100 deaths and 33.130 expected new
cases in United States for the 2007), encompassed among
highly vascularised tumors [1,2]. Furthermore the
common use of cross-sectional imaging method in clinical
practise has increased the detection of incidental small
RCC [3,4].
Minimally invasive treatments as cryoablation or
radioablation have been proposed as a promising alternative to
partial or total nephrectomy in selected cases, especially in
patients who are poor candidates for conventional
surgical resection. Cryoablation of renal tumors can be
performed at open, laparoscopic, retroperitoneoscopic
surgery and with imaging guided (Computed
Tomography, CT; Magnetic Resonance Imaging, MRI)
percutaneous approaches. By the evidence of effectiveness in renal
tumor constraining of these new thermal therapies,
attention is focused to identify a reliable marker of early
residual tumor and a feasible imaging monitoring protocol.
Vascularity degree of RCC is known as a prognostic factor
correlated with clinical and pathologic stage, metastatic
risk and histopathologic grade and it is a significant
predictor of disease-specific outcome after therapy [5].
Although a standardized and thoroughly validated
method to evaluate tumor vascularity is not available,
some biomarkers have been currently proposed as indexes
of tumor angiogenic activity. In particular, significant
increase of micro vessel density (MVD) and high
expression and secretion of vascular endothelial growth factor
(VEGF), have been reported in tumor tissue [6]. However,
the serial evaluation of these biomarkers as indexes of
tumor activity, needs multiple biopsies and is limited
because of its invasiveness especially during a long-term
follow-up.
An ideal test should be non-invasive, fast, easy to perform,
repeatable and reproducible, and most importantly, it
should provide in vivo early evidence of residual tumor
after therapy and comprehensive data of the tumor
structure with informations on tumor angiogenesis functional
status.
New imaging modalities (MRI, CT) may be used to obtain
informations about microvascular circulation and
neoangiogenesis. CT is the imaging technique of reference in
surveillance after renal tumor ablation as its ability to
distinguish residual tumor (nodular enhancement within
the ablated lesion) from successfully cryo-ablated lesion
(hypoattenuating areas without focal contrast
enhancement with progressive (...truncated)