Clinical Symposium 1. Update in liver imaging LI-RADS (Liver Imaging-Reporting and Data System) 최진영 연세대학교의과대학영상의학과 Abstract Contrast-enhanced CT and MRI are frequently used for the noninvasive diagnosis of hepatocellular carcinoma (HCC). Currently, findings at liver imaging are inconsistently interpreted and reported by most radiologists. In 2008, the American College of Radiology convened a committee to develop a standardized system, which is Liver Imaging-Reporting and Data System (LI-RADS). The aim of LI-RADS is to reduce variability in lesion interpretation by standardizing report content and structure, improving communication with clinicians, and facilitating decision making, outcome monitoring, performance auditing, and research. Five categories that follow the diagnostic thought process are used to stratify individual observations according to the level of concern for HCC. This essay provides an overview of the LI-RADS, initial consensus of the LI-RADS management working group, and discordance of LI-RADS with AASLD guidelines. 서론 최근 CT나 MRI와같은영상기법의발달로간세포암의진단정확도가상승하면서비침습적진단기준의중요성이증가하고있다. 그러나영상소견에대한해석과보고서의통일된양식이없어같은해석도다른용어를사용하거나관찰한소견이일관적으로해석되지않아각기관별, 기관내, 판독자간영상소견을비교하기어렵다. 1 구조화된영상보고서를사용하면영상소견에관한의사소통이분명해지고표준화되며각관찰소견의특징등을추적할수있다. 이러한구조화된시스템을처음적용한분야는유방영상으로 breast imaging-reporting and data system (BI-RADS) 는유방질환을가진환자의진단과치료에매우유용하며성공적인도구가되었다. BI-RADS의성공적인적용후간세포암에대해서도 liver imaging-reporting and data system (LI-RADS) 가개발되어발전되는단계에있다. LI-RADS의목적은병변의해석에대한가변성을 26 대한간학회
최진영 LI-RADS (Liver Imaging-Reporting and Data System) 줄이고임상가간에의사소통을향상시키며임상적상황결정에도움을주기위한것이다. 또한영상검사의정보를빠뜨리지않고표준화하며, 결과를추적하고질적향상과연구를용이하게하기위함이다. 2 본론 1. LI-RADS 개괄 LI-RADS는간세포암의위험도에따라각영상소견을 5가지중하나의카테고리로분류한다. 3 병변 (lesion) 대신소견 (observation) 이라는용어를사용한다. LI-RADS 카테고리는분명한간세포암을 LR-5로, 분명한양성병변을 LR-1으로분류한다 ( 표 1). 일부의영상소견이간세포암을시사하면 LR-4 (probably HCC), 일부의소견이양성을시사하면 LR-2 (probably benign) 으로구분한다. LR-3는애매한소견으로양성이나간세포암을시사하는특이소견이없는경우이다. 종양의특성이간세포암이외의악성 ( 예. 담관암 ) 을시사하면 LR-M으로분류하고대개조직검사를필요로한다. 정맥내에분명한종양이있는경우에는일차성종양이보이지않더라도 LR-5V로분류한다. LR-5는분명한간세포암으로영상의학과의사가 100% 확신하는경우이다. 이는높은특이도를유지하기위한것으로특히 1-2 cm크기의결절에서 AASLD의기준에비해엄격한기준을적용한다. 4 LR-4는 표 1. Summary of liver imaging and reporting data system (version 2014) category codes LI-RADS category code LR1: definitely benign LR2: probably benign LR3: intermediate probability for HCC LR4: probably HCC LR5: definitely HCC LR5V: definitely HCC with tumor in vein LR5 treated: treated HCC OM Concept and definition Concept: 100% certainty observation is benign. Definition: Observation with imaging features diagnostic of a benign entity, or definite disappearance at follow up in absence of treatment. Concept: High probability observation is benign. Definition: Observation with imaging features suggestive but not diagnostic of a benign entity. Concept: Both HCC and benign entity have moderate probability. Definition: Observation that does not meet criteria for other LI-RADS categories. Concept: High probability observation is HCC but there is not 100% certainty. Definition: Observation with imaging features suggestive but not diagnostic of HCC. Concept: 100% certainty observation is HCC. Definition: Observation with imaging features diagnostic of HCC or proven to be HCC at histology. Concept: 100% certainty that observation is HCC invading vein. Definition: Observation with imaging features diagnostic of HCC invading vein. Concept: A loco-regionally treated HCC. Definition: LR5A or 5B observation or biopsy-proven HCC lesion that has undergone loco-regional treatment. Concept: High probability that observation is a malignancy other than HCC. Definition: Observation with features suggestive of non-hcc malignancy. www.kasl.org 27
2014 년대한간학회추계학술대회 그림 1. LI-RADS 2014. probable HCC의카테고리로관찰소견이간세포암일가능성이높으나 100% 확신할수없는경우이다. 간세포암중 LR-5의기준을충족하지못하는경우나간세포암으로진단하는데조금이라도의심이들면 LR-4나그이하의카테고리로분류한다. LI-RADS의분류기준은주로병변의크기와 4가지주요소견을바탕으로한다 ( 그림 1): 동맥기과혈관성, 문맥기나지연기의씻김, 피막모양과이전영상과한계성장 (threshold growth). 2. 간세포암을시사하는주요소견동맥기과혈관성 : 동맥기에주변간실질에비해서전체또는부분적으로조영증강이증가한경우를과혈관성이라고정의한다. 동맥기과혈관성은간세포암환자에서가장일관적이고중요한소견으로간주된다. 이특징은단계적간세포암화과정에서신생혈관의발달을반영하는것으로생각된다. 문맥기또는지연기조영감소또는씻김 : 이소견역시동맥기의과혈관성과더불어강력하게간세포암을시사하는소견이다. 문맥기나지연기의조영감소는조영제의조기혈관유출과함께간세포암에서문맥공급의감소에의한것으로생각된다. 문맥기또는지연기의조영감소는동맥기에과혈관성을보인 28 대한간학회
최진영 LI-RADS (Liver Imaging-Reporting and Data System) 부분과같은부위를비교해서결정해야한다. 피막모양 : 문맥기나지연기에바깥쪽의매끈한고음영의띠로주변간경변성결절의띠에비해두꺼워야한다. AASLD나 EASL에서는피막을간세포암의진단기준에포함시키지않았으나 LI-RADS와 organ procurement and transplantation network (OPTN) 에서는피막모양을주진단소견으로간주한다. 한계성장 (threshold growth): 최소 5mm이상직경이커지거나 6개월이내직경의 50% 이상, 6개월이상인경우 100% 이상직경이증가하면한계성장으로간주한다. 1cm이상의새로운병변이나타나면기간에상관없이한계성장을의미한다. 부가적소견들 : 간세포암을선호하는부가소견은다음과같다-mild to moderate T2 hyper-intensity, restricted diffusion, corona enhancement, mosaic architecture, nodule-in-nodule architecture, intra-lesional fat, lesional iron sparing, lesional fat sparing, blood products, diameter increase less than threshold growth. 이들소견들에따라간세포암의가능성이변동될수있으나카테고리를나눌만큼믿을만한소견은아니므로부가적소견으로간주한다. 이들부가소견이보이면하나또는두단계의카테고리를높일수있으나 LR-4를넘지는못한다. 양성병변을시사하는소견이있을때도하나또는두단계로카테고리를낮출수있다. LIRADS management working group의다음합의사항이기본개념의이해에도움이될것이다. 4 a. EASL과 AASLD의가이드라인은영상기준에의해분명한간세포암에관한치료에관해서기술하였으나 LI-RADS는 indeterminate 카테고리를양성추정, 중등도확률의간세포암, 간세포암추정 (LIRADS 2,3,4) 으로확장하였다. LIRADS의카테고리는간세포암의감시프로그램에속하는대상자에만적용되고간세포암의위험도가낮은환자에서우연히발견된병변에대해서는적용하지않는다. b. LI-RADS분류는조영증강 CT나 MRI의소견을바탕으로하였고다른임상적또는영상학적소견과상관없다. 그러나분명한간세포암이아닌관찰 (observation) 에대해서임상의는 LI-RADS분류뿐아니라종양표지자같은다른소견을참고하여간세포암의확률을추정할수있다. c. 추적검사기간을줄이거나, 다른영상검사를하거나, 조직검사또는조직검사없이치료등의결정은 LI-RADS 분류나임상의의추정에만따르지말고동반된다른질환등모든가능한임상정보를고려하여종합적판단을해야한다. 3. AASLD 나다른가이드라인과의차이 1) AASLD 가이드라인에서는초음파에서발견된 10mm이상의결절은조직검사를하거나다른영상검사로평가하도록하고다른검사에서도결론을내리지못하면조직검사를하도록권고하고있다. 그러나 10mm 이상의 indeterminate nodule을조직검사하는것이추적관찰하는것에비해생존률을증가시킨다는증거가없고조직검사를해석하는데일치도가매우낮으며위양성, 위음성의위험이있음을고려해야한다. LI-RADS에서는간세포암의확률이낮은병변과높은병변에관해서다른관리를할수있도록기준과용어를사용한다 (5). 예를들어크기가작은위험도가낮은병변의경우중복된검사나조 www.kasl.org 29
2014 년대한간학회추계학술대회 직검사를피하고악성이라도치료시기를놓치지않도록적절한간격으로추적검사를하도록한다. 2) AASLD 가이드라인은연속적인초음파검사를바탕으로감시검사를해서발견된병변으로국한되어있으나실제로는다양한이유로역동적 CT나 MRI검사가감시검사로사용되고있다. 일본간암학회에서는위험도가매우높은환자에서는초음파검사가간경변이나비만등으로제한적이므로 CT나 MRI 를감시검사에사용하도록하고있다. LI-RADS는이전초음파에서병변의발견여부에상관없이 CT나 MRI에서의결과를기준으로한가이드라인을제시한다. 3) AASLD 가이드라인은초음파검사에서발견된 1-2 cm크기의결절이동맥기과혈관성과씻김의소견을보이면간세포암으로진단하도록하였으나이후의연구들에서이들병변중고등급이형성결절이나담관세포암등이포함될수있어특이도를보장할수없다. 1-2 cm크기의병변에서위양성의빈도를줄이기위해 LI-RADS에서는이들병변을 LR-4로분류하였는데 AASLD 가이드라인과다르게해석할가능성이있었다. LI-RADS 2014에서는이런불일치를해결하기위해 LR-5us (us=ultrasound) 의카테고리를만들어영상의학과의사가이결절이처음감시초음파검사에서발견된병변이라는것을표시하도록하였다. 또한 LR-5g는 6개월이내에 50% 이상의한계성장을보이는결절로정의하였다. 현재의 LI-RADS는간세포암의위험이있는환자에만적용된다. 현재까지의기준은세포외액조영제를사용한 CT나 MRI에만적용되고간세포특이조영제인 Gd-EOB-DTPA는아직까지이시스템에포함되지않았다. 또한향후 LI-RADS 분류에서의각관찰소견에관한일치도에관한연구가필요하다. 6,7 References 1. Tang A, Cruite I, Sirlin CB. Toward a standardized system for hepatocellular carcinoma diagnosis using computed tomography and MRI. Expert Rev Gastroenterol Hepatol 2013;7(3):269-279. 2. Purysko AS, Remer EM, Coppa CP, Leao Filho HM, Thupili CR, Veniero JC. LI-RADS: a case-based review of the new categorization of liver findings in patients with end-stage liver disease. Radiographics 2012;32(7):1977-1995. 3. Santillan CS, Tang A, Cruite I, Shah A, Sirlin CB. Understanding LI-RADS: a primer for practical use. Magn Reson Imaging Clin N Am 2014;22(3):337-352. 4. Mitchell DG, Bruix J, Sherman M, Sirlin CB. LI-RADS (Liver Imaging Reporting and Data System): Summary, discussion, consensus of the LI-RADS Management Working Group and future directions. Hepatology 2014. 5. Choi JY, Cho HC, Sun M, Kim HC, Sirlin CB. Indeterminate observations (liver imaging reporting and data system category 3) on MRI in the cirrhotic liver: fate and clinical implications. AJR Am J Roentgenol 2013;201(5):993-1001. 6. Davenport MS, Khalatbari S, Liu PS, et al. Repeatability of diagnostic features and scoring systems for hepatocellular carcinoma by using MR imaging. Radiology 2014;272(1):132-142. 7. Petruzzi N, Mitchell D, Guglielmo F, et al. Hepatocellular carcinoma likelihood on MRI exams: evaluation of a standardized categorization system. Acad Radiol 2013;20(6):694-698. 30 대한간학회