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IMAGING
Renal
cell carcinoma: dynamic contrast-enhanced MR imaging for differentiation
of tumor subtypes--correlation with pathologic findings
Sun MR, Ngo L, Genega EM, Atkins MB, Finn ME, Rofsky NM, Pedrosa I
Department of Radiology, Beth Israel Deaconess Medical Center, Boston,
MA, USA
Radiology. 2009; 250: 793-802
- Purpose:
To retrospectively evaluate whether the enhancement patterns of pathologically
proved clear cell, papillary, and chromophobe renal cell carcinomas
(RCCs) measured on clinical dynamic contrast agent-enhanced magnetic
resonance (MR) images permit accurate diagnosis of RCC subtype.
-
Materials and Methods:
This study was Institutional Review Board approved and HIPAA compliant;
informed consent was waived. One hundred twelve patients (76 men, 36
women; age range, 25-88 years; mean age, 58.1 years) underwent MR imaging
of 113 renal masses (mean diameter, 5.4 cm) with pathologic diagnoses
of clear cell (n = 75), papillary (n = 28), or chromophobe (n = 10)
RCC. A 1.5-T clinical MR protocol was used before and after (corticomedullary
and nephrographic phases) intravenous administration of contrast agent.
Region-of-interest measurements within tumor and uninvolved renal cortex
were used to calculate percentage signal intensity change and tumor-to-cortex
enhancement index. Subtype groups were compared by using linear mixed-effects
models. Receiver operating characteristic (ROC) curve analysis was performed
for the comparison of clear cell and papillary RCCs.
-
Results:
On both the corticomedullary and nephrographic phase images, clear cell
RCCs showed greater signal intensity change (205.6% and 247.1%, respectively)
than did papillary RCCs (32.1% and 96.6%, respectively) (P < .001).
Chromophobe RCCs showed intermediate change (109.9% and 192.5%, respectively).
The tumor-to-cortex enhancement indexes at corticomedullary and nephrographic
phases were largest for clear cell RCCs (1.4 and 1.2, respectively),
smallest for papillary RCCs (0.2 and 0.4, respectively), and intermediate
for chromophobe RCCs (0.6 and 0.8, respectively). Signal intensity changes
on corticomedullary phase images were the most effective parameter for
distinguishing clear cell and papillary RCC (area under ROC curve, 0.99);
a threshold value of 84% permitted distinction with 93% sensitivity
and 96% specificity.
-
Conclusion:
Clear cell, papillary, and chromophobe RCCs demonstrate different patterns
of enhancement on two-time point clinical dynamic contrast-enhanced
MR images, allowing their differentiation with high sensitivity and
specificity.
- Editorial
Comment
Each subtype of RCC is associated with a different prognosis and tumor
behavior. If possible, preoperative characterization of RCC subtypes
would influence the degree of preoperative evaluation and the determination
of the appropriate extent of surgery (1-3). For example a patient with
a subtype that tends to not metastasize or recur, such as the chromophobe,
may not need to undergo a complex metastasis survey and unnecessarily
wide resection may be avoided, thereby, decreasing postoperative morbidity
and mortality (3). For this reason, adequate preoperative characterization
of the RCC subtype has been attempted utilizing contrast enhanced CT
studies (2,3). On multiphase contrast enhanced the clear cell (70.3%)
and papillary (69.2%) subtypes tended to show heterogeneous or predominantly
peripheral enhancement, whereas the chromophobe subtype (75%) usually
showed homogeneous enhancement.
The authors of this excellent original study found in a study of 112
patients that clear cell, papillary, and chromophobe renal cell carcinoma
demonstrated different enhancement patterns when assessed with 3D T1-weighted
spoiled gradient-echo sequences before and after (corticomedullary and
nephrographic phases) contrast material administration. It is interesting
to note that differently from contrast enhanced CT studies, the best
results of this dynamic contrast enhanced MR technique was accomplished
using analysis of signal intensity in the corticomedullary phase.
As the author mentioned in the text, if their results are confirmed
with a larger prospective study, this method would provide equivalent
accuracy to that reported for percutaneous biopsy. Probably both techniques
will be used together in the preoperative evaluation of renal mass since
percutaneous biopsy is the only technique that provides Fuhrman grade
immunohistochemical stain.
References
1. Reuter VE, Presti JC Jr: Contemporary approach to the classification
of renal epithelial tumors. Semin Oncol. 2000; 27: 124-37.
2. Sheir KZ, El-Azab M, Mosbah A, El-Baz M, Shaaban AA: Differentiation
of renal cell carcinoma subtypes by multislice computerized tomography.
J Urol. 2005; 174: 451-5; discussion 455.
3. Kim JK, Kim TK, Ahn HJ, Kim CS, Kim KR, Cho KS: Differentiation of
subtypes of renal cell carcinoma on helical CT scans. AJR Am J Roentgenol.
2002; 178: 1499-506.
Dr.
Adilson Prando
Chief, Department of Radiology and
Diagnostic Imaging, Vera Cruz Hospital
Campinas, São Paulo, Brazil
E-mail: adilson.prando@gmail.com |