Chulalongkorn Medical Journal


Background : Renal cell carcinomas (RCC) represent about 1 - 3% of allvisceral cancers and 85% of renal cancers in adults. The tumorsoccur most often in old age, usually in sixth and seventh decadesof life, and more predominantly in males. There are differentprognosis between each subtype of RCC and different targetedtherapy of choice for clear cell and non-clear cell subtypes ofRCC. Subtype differentiation of RCC is quite important for guidedtreatments and predicted prognosis. (according to the NCCN’sClinical Practice Guideline for Renal Cancer 2009).Objective : This study aims to differentiate clear cell subtype of RCC fromother subtypes on multiphase MDCT scans.Setting : The Department of Radiology and Department of Pathology,Faculty of Medicine, Chulalongkorn University, Bangkok 10330,Thailand.Research design : Retrospective-Descriptive studyMaterial and Methods : We reviewed CT scans of all RCC subtypes covering 33 clearcellRCC, 12 papillary RCC and 4 chromophobe RCC. NineteenCT scans, which consist of unenhanced, corticomedullaryphase (CMP) and nephrographic phase (NP) scans and 28CT scans (unenhanced, angiographic phase, CMP, NP andexcretory phase scans) are included in the study. We comparedtumor size, enhancement patterns, degree of tumor enhancementin these subtypes.Results : Enhancement ratio in CMP and NP and absolute tumorenhancement in CMP are significantly different between clear -cell RCC and other RCCs (P < 0.05). We did not find anysignificance of absolute tumor enhancement in NP betweenclear- cell RCC and other RCCs. The sensitivity and specificityfor differentiating clear- cell RCC from other RCCs were 75.8%and 75% when enhancement ratio of 0.45 was used as thecutoff value in the CMP and 75.8% and 62.5% when enhancementratio of 0.43 was the cutoff value in the NP. The sensitivity andspecificity for differentiating clear- cell RCC from other RCCswere 75.8% and 75% when absolute tumor enhancement of48.8 HU was used as the cutoff value in CMP.Conclusions : The enhancement ratio in CMP can be used for differentiatingclear- cell RCC from other RCCs with equal sensitivity andspecificity to absolute tumor enhancement in CMP. However,the area under the ROC curves of enhancement ratio is morethan that of tumor absolute enhancement. Hence, theenhancement ratio could be superior to absolute tumorenhancement value for differentiating clear -cell RCC from othersubtypes.


Faculty of Medicine, Chulalongkorn University

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