Korean J Lab Med 2010;30:533-9 DOI 10.3343/kjlm.2010.30.6.533 Original Article Diagnostic Hematology Minimal Residual Disease Detection in Acute Leukemia Patients by Flow Cytometric Assay of Cross-lineage Antigen Expression Young-Uk Cho, M.D. 1,4, Chan-Jeoung Park, M.D. 1, Choong-Hwan Cha, M.D. 1,5, Hyun-Sook Chi, M.D. 1, Seongsoo Jang, M.D. 1, Mi-Jung Kim, Ph.D. 1, Kyoo-Hyung Lee, M.D. 2, Je-Hwan Lee, M.D. 2, Jung-Hee Lee, M.D. 2, Jong Jin Seo, M.D. 3, and Ho Joon Im, M.D. 3 Departments of Laboratory Medicine 1, Internal Medicine 2, and Pediatrics 3, University of Ulsan College of Medicine and Asan Medical Center, Seoul; Department of Laboratory Medicine 4, Eulji General Hospital, Eulji University School of Medicine, Seoul; Department of Laboratory Medicine 5, Gangneung Asan Hospital, Gangneung, Korea Background : It has been demonstrated that flow cytometric detection of minimal residual disease (MRD) has a prognostic significance in the treatment of patients with acute leukemia. We investigated the significance of flow cytometric MRD detection for the first time in Korea. Methods : We analyzed the results of MRD detection in morphologically complete remission bone marrow aspirates from 89 patients with newly-diagnosed or relapsed acute leukemia, in which leukemic cells had cross-lineage antigen expression. Patients were grouped based on MRD frequencies: 1.0%, high MRD; <1.0%, low MRD. Results : Forty-seven ALL patients consisted of 10 with high and 37 with low MRD levels. Patients with high MRD levels showed a tendency of more frequent relapse than those with low MRD levels (40.0% and 13.5%, respectively) (P=0.08). High MRD group showed a tendency of short relapsefree survival (RFS) and overall survival (OS), although the differences were not statistically significant. Forty-two AML patients consisted of 16 with high and 26 with low MRD levels. There were no correlations between the MRD levels and relapse rate, RFS or OS. AML patients with high MRD levels showed significantly higher rate of unfavorable cytogenetic risk categories and lower rate of favorable risk categories (P=0.03). Conclusions : MRD detection by flow cytometric assay of cross-lineage antigen expression would be useful in predicting treatment outcome in patients with ALL rather than AML. We expect that the establishment of the standardization of methods, time to test or antibody combination would be achieved through further trials in this country. (Korean J Lab Med 2010;30:533-9) Key Words : Minimal residual disease, Acute leukemia, Flow cytometric assay, Cross-lineage antigen expression 서 론 급성백혈병의치료에서완전관해의정의는주로형태학적관 Received : April 15, 2010 Manuscript No : KJLM10-067 Revision received : August 31, 2010 Accepted : October 20, 2010 Corresponding author : Chan-Jeoung Park, M.D. Department of Laboratory Medicine, Asan Medical Center, 388-1 Poongnap 2-dong, Songpa-gu, Seoul 138-736, Korea Tel : +82-2-3010-4508, Fax : +82-2-478-0884 E-mail : cjpark@amc.seoul.kr *This study was supported in part by grant the National R&D Program for Cancer Control (0520290) from the Ministry of Health & Welfare of Korea. ISSN 1598-6535 The Korean Society for Laboratory Medicine 찰에의존하고있다. 그러나형태학적접근은재발의원인이되는소수의잔존백혈병세포를민감하게검출할수없을뿐더러관찰자의주관이개입되어객관성을확보할수없다는한계를지니고있다. 그러므로잔존백혈병세포의정도를민감하고객관적으로측정하여치료효과를보다정확하게평가할수있다면이에근거하여적절한치료가가능하다. 즉관해유도치료후높은미세잔존질환 (minimal residual disease, MRD) 을보이는경우, 보다강화된치료를통해재발의위험도를낮추어생존율을높일수있고, 치료후미세잔존질환이거의측정되지않는경우라면항암제의종류또는용량을조절하여부작용을줄이면서도향상된치료효과를꾀할수도있다. 533
534 Korean J Lab Med 2010;30:533-9 유세포분석 (flow cytometry) 은현재급성백혈병의 MRD 측정을위해널리사용되고있다. 백혈병세포는정상혈액이나골수세포에서는발현되지않거나매우드물게발현되는면역표현형을보이는데, 이를백혈병연관표현형 (leukemia-associated phenotype, LAP) 이라한다. 대표적인 LAP로는하나의세포에분화초기와후기의항원이혼재하는항원표현의부조화 (asynchronous antigen expression), 골수성백혈병세포에림프모구백혈병세포의항원이표현되는또는림프모구백혈병세포에골수성항원이표현되는교차계열항원표현 (cross-lineage antigen expression), 항원의과표현, 계열특이항원의소실등이있다 [1]. 유세포분석을통한 MRD 모니터링은이러한 LAP를측정함으로써이루어진다 [1-5]. 유세포분석에의한면역표현형검사는이미급성백혈병의진단및분류에있어필수적인도구로정착되어있다. 외국에서는초기진단에서한발더나아가 1990년대후반부터급성백혈병에서유세포분석을이용한 MRD 측정에대한많은연구가시도되어재발위험도또는생존예측및치료방식선택에있어유용하다는보고가지속적으로이루어지고있다 [6-22]. 반면국내에서는이에대한연구가아직미진하여저자들이검색한바로는유세포분석을이용한급성백혈병의 MRD 측정에관한보고가아직없고, 단지 급성백혈병의완전관해골수에서항원성이상세포의분포 에관한보고가있을뿐이다 [23]. 따라서국내에서도유세포분석을활용한급성백혈병의 MRD 측정이급성백혈병의치료후예후예측및치료방침결정에이용되어질병극복에기여하여야할것으로생각한다. 이에저자들은단일기관급성백혈병환자들을대상으로유세포분석을이용한 MRD 측정의의의를분석하고, 이를통해향후국내검사실에서도유세포분석 MRD 측정이활발히시행되어일상검사로정착되는데도움이되고자하였다. 재료및방법 1. 대상군및검체급성백혈병으로처음진단되었거나형태학적으로재발한환자들중처음진단또는재발시면역표현형검사에서정상골수에서발현되지않는교차계열항원이표현되며, 관해유도치료후형태학적관해판정을받은환자들을대상으로하였다. 급성백혈병의진단당시사용한면역표현형검사의패널은 Table 1 과같다. 2004년 5월부터 2007년 2월까지 47명의 ALL 환자와 42명의 AML 환자를대상으로하였다. MRD는관해유도또는 Table 1. Monoclonal antibody panel for immunophenotyping of acute leukemia FITC PE PerCp APC AML CD14 CD33 CD41 CD45 CD65 CD10 CD3 CD45 CD56 CD117 CD34 CD45 CD19 CD13 CD7 CD45 CD15 CD2 - CD45 TdT cytocd22 cytocd3 - ALL CD2 CD13 CD7 CD45 CD56 CD33 CD3 CD45 CD19 CD10 CD34 CD45 CD5 CD20 - CD45 TdT cytocd22 cytocd3 - - surfaceigm - - - cytoigm - - Abbreviations: FITC, fluorescein isothiocynate; PE, phycoerythrin; PerCp, peridinin-chlorophyll-protein; APC, allophycocyanin. 공고요법항암치료후형태학적으로완전관해소견을보인골수검체로측정하였다. 2. 유세포분석을이용한 MRD 측정 MRD 검출을위한유세포분석검사는진단시나타난교차계열항원양상을이용하여단클론항체를조합하여형광염색을시행하였다. 이때양성인교차계열항원으로 4색형광조합을만들기위하여진단시사용한형광결합항체외에도 CD33- FITC, CD7-FITC, CD19-PE를추가로사용하였다. 형광염색후적혈구를용혈시킨다음혈소판과세포부스러기 (debris) 가분석에서제외되도록역치 (threshold) 를정하여입력하고, 20,000개의세포를획득하였다. MRD 측정은 Kern 등 [24] 이고안한연속 gating법으로분석하였다. 첫째단계로백혈병세포의형태학적특징을고려하여 CD45가약양성이거나음성이며낮은 side scatter 영역에분포하는세포들을 gating하였고, 둘째단계는 gating된세포에서다수의백혈병세포가양성인계열별양성세포 (AML의경우 CD13/CD34 또는 CD33/CD34, B계열 ALL의경우 CD19/CD34, T계열 ALL의경우 CD7/ CD34, 드물게 CD34가음성인경우주계열양성표지자 /side scatter cytogram [SSC]) 을다시 gating한다음, 셋째단계에서두번째 gating된세포가운데교차계열항원양성을보이는세포를측정하여전체유핵세포에서의백분율로나타내었다. Fig. 1과같이진단당시 CD13양성골수모구가 CD19양성소견을보인경우, 항암화학요법후형태학적으로완전관해를나타내는골수를 CD19-FITC/CD13-PE/CD34-PerCP/CD45-
Cho Y-U, et al., Flow Cytometric MRD Detection 535 CD13 PE 10 5 10 4 10 3 Leukemic cells with coexpression of CD13 and CD19=91.87% CD13 PE 10 5 10 4 10 3 MRD=4.33% CD13 PE 10 5 10 4 10 3 MRD=0.01% 10 2 10 2 10 2 10 2 10 3 10 4 10 5 10 2 10 3 10 4 10 5 10 2 10 3 10 4 10 5 CD19 FITC A CD19 FITC B CD19 FITC C Fig. 1. MRD detection in the bone marrow aspirates from an ALL patient at diagnosis (A), and patients with morphological remission (B and C). The leukemia-associated phenotype includes CD13 and CD19 expression. The MRD levels were 4.33% (B) and 0.01% (C). Abbreviations: PE, phycoerythrin; FITC, fluorescein isothiocynate; MRD, minimal residual disease. Table 2. Characteristics of patients with acute leukemia Characteristics ALL patients (N=47) AML patients (N=42) Age (yr) 7 (1-62) 41 (1-69) Pediatric/adult 32/15 7/35 Sex (M/F) 33/14 25/17 Cross-lineage antigen expression* CD13 20 CD7 14 CD13 & CD33 15 CD56 & CD19 8 CD33 5 CD56 8 Others 7 CD19 4 Others 8 Cytogenetic risk categories Favorable 19 18 Intermediate 12 18 Unfavorable 11 4 Unknown 5 2 Follow-up duration (months) 14 (3-40) 12 (3-28) All continuous variables are expressed as median (range). *Fluorochromes conjugated with monoclonal antibody: CD13-PE, CD33-PE or FITC, CD3-PerCP, CD7-PerCP or FITC, CD19-FITC or PE, CD56-FITC; CD7 in 3 patients; CD7 & CD13 in 2 patients; CD56 in 1 patient; CD7 & CD33 in 1 patient; CD7 & CD56 in 5 patients; CD7 & CD19 in 2 patients; CD10 & CD56 in 1 patient. APC로염색하여 CD45 dim/ssc low로 gating하고, 다시 CD13+/CD34+ 로 gating한다음, CD19/CD13 cytogram을분석하여, CD19+/CD13+ 양성인 CD19 양성골수모구의전체유핵세포에서의백분율을구하였다. 사용한유세포분석기는 FAC- SCanto (Becton Dickinson, San Jose, CA, USA) 였고, 분석소프트웨어는 FACS Diva (Becton Dickinson) 였다. MRD의임상적유용성을평가하고자 MRD 수준이높은군과낮은군으로나누어재발, 무재발생존기간, 전체생존기간을비교하였다. 두군을나누는기준은다른연구자들의기준을참고하였고 [7, 13], MRD 결과의분포와분석의편의를고려하여 0.1%, 0.5%, 1.0% 로각각설정하여분석하였다. 또한임상경과및예후를결정하는중요인자로알려져있는세포유전학적소견과의관련성도분석하였다. 3. 통계분석 MRD 크기에따른환자군의비교에는연속변수의경우 Mann- Whitney test를, 순위변수의경우 Fisher s exact test를이용하였다. 무재발생존곡선및전체생존곡선분석은 Kaplan-Meier 방법을이용하여평가하였다. 모든통계분석은 MedCalc version 9.1.0.1 (MedCalc Software, Mariakerke, Belgium) 를사용하였으며, 유의수준은 P<0.05로하였다. 결과대상군의특성은 Table 2에요약하였다. 높은 MRD의 3가지기준들중 1.0% 를적용하였을때, 0.5% 와 0.1% 보다상대적으
536 Korean J Lab Med 2010;30:533-9 Table 3. Clinical characteristics according to the MRD levels MRD group ALL patients AML patients N Relapse (%) RFS (months) OS (months) N Relapse (%) RFS (months) OS (months) High ( 1.0%) 10 4 (40.0)* 9.9 10.9 16 5 (31.3) 8.8 9.7 Low (<1.0%) 37 5 (13.5)* 13.3 13.8 26 5 (19.2) 9.2 12.8 High ( 0.5%) 14 4 (28.6) 10.0 10.6 22 5 (22.7) 8.4 8.8 Low (<0.5%) 33 5 (15.2) 13.5 14.0 20 5 (25.0) 9.4 13.6 High ( 0.1%) 35 7 (20.0) 10.0 10.5 34 7 (20.6) 8.6 9.7 Low (<0.1%) 12 2 (16.7) 16.7 16.9 8 3 (37.5) 9.6 15.5 All continuous variables are expressed as median. *P=0.08; P=0.46. Abbreviations: MRD, minimal residual disease; RFS, relapse-free survival; OS, overall survival. 100 100 95 90 Survival probability (%) 90 85 80 75 70 MRD H L Survival probability (%) 80 70 60 50 40 MRD H L 65 0 10 20 30 40 50 Time (months) A 30 0 10 20 30 40 50 Time (months) B Fig. 2. Prognostic significance of minimal residual disease (MRD) frequency in bone marrow aspirates after morphological remission in ALL patients. (A) High MRD group showed a tendency of shorter relapse-free survival (RFS) than low MRD group using a cutoff level of 1.0% (P=0.11). (B) High MRD group also showed a tendency of shorter overall survival (OS) than low MRD group (P=0.54). Table 4. Distribution of the MRD groups according to the time of sample collection MRD group Postinduction (N=26) ALL patients Post-consolidation (N=21) Abbreviation: MRD, minimal residual disease. AML patients Postinduction (N=27) Post-consolidation (N=15) High ( 1.0%) 3 6 9 7 Low (<1.0%) 23 15 18 8 로높은임상적분별력을보였다 (Table 3). MRD 1.0% 를기준으로하였을때, ALL 환자군에서높은 MRD군이 10명, 낮은 MRD군이 37명이었다. 임상경과중재발은높은 MRD군에서 4명 (40.0%), 낮은 MRD군에서 5명 (13.5%) 으로높은 MRD군에서재발률이높은경향을보였다 (P=0.08). 무재발생존및전체생존기간의중앙값은높은 MRD군에서각각 9.9개월과 10.9 개월로낮은 MRD군의 13.3개월과 13.8개월에비해불량한결 과를보였으나통계적으로유의한차이는없었다 ( 각각 P=0.11 과 P=0.54) (Table 3, Fig. 2). AML 환자군의경우높은 MRD 군이 16명, 낮은 MRD군이 26명이었다. 추적기간중재발은높은 MRD군에서 5명 (31.3%), 낮은 MRD군에서 5명 (19.2%) 으로높은 MRD군에서상대적으로높은재발률을보였으나통계적으로유의한차이는없었다 (P=0.46). 무재발생존및전체생존기간의중앙값은높은 MRD군에서각각 8.8개월과 9.7개월, 낮은 MRD군에서각각 9.2개월과 12.8개월로통계적으로유의한차이는없었다 ( 각각 P=0.39과 P=0.24) (Table 3). 검체채취시기에따른 MRD군분포의통계학적차이는없었다 (Table 4). ALL 환자의경우 MRD 정도와세포유전학적예후군 [25] ( 양호군, 불량군, 표준예후군 ) 분포와의상관성이없었다. 그러나, AML 환자에서는높은 MRD군에서낮은 MRD군보다세포유전학적예후불량군의빈도가높았고, 양호군의빈도가낮았던반면, 낮은 MRD군에서는그반대의결과를보여통계적으로유의한차이를나타내었다 (P=0.03) (Table 5).
Cho Y-U, et al., Flow Cytometric MRD Detection 537 Table 5. Relation between MRD groups and cytogenetic risk categories MRD group Cytogenetic risk categories in ALL patients (P=0.29) Cytogenetic risk categories in AML patients (P=0.03) F I U US F I U US High ( 1.0%) 6 (60.0%) 1 (10.0%) 2 (20.0%) 1 (10.0%) 3 (18.8%) 9 (56.3%) 3 (18.8%) 1 (6.3%) Low (<1.0%) 13 (35.1%) 11 (29.7%) 9 (24.3%) 4 (10.8%) 15 (57.7%) 9 (34.6%) 1 (3.8%) 1 (3.8%) Abbreviations: MRD, minimal residual disease; F, favorable; I, intermediate; U, unfavorable; US, unknown significance. 고찰급성백혈병의치료에있어정기적인골수검사를통한치료효과판정은필수적인요소이다. 그러나백혈병세포와정상적인조혈계전구세포를형태학적으로완벽하게판별하는것은아무리숙련된진단검사의학전문의에게도거의불가능한일이기때문에, 아세포가관찰되더라도유핵세포감별계산의 5% 미만이면형태학적완전관해로판정하고있다. 따라서형태학적완전관해판정을받은일부환자에서실제로는상당한수준의백혈병세포가잔존해있을가능성이있으며, 이러한환자들은생물학적으로필요한치료보다낮은수준의치료를받을수있다 [4]. 이와는반대로백혈병세포수를과다하게판정한경우에는불필요한강화치료를실시하여결과적으로항암치료의독성에노출될가능성이있다 [4]. 최근 10여년간급성백혈병치료후 MRD를보다민감하고객관적으로측정할수있는방법및이의의의에대한연구들이이루어져왔다. 현재세포표면항원을분석하는유세포분석과유전자의클론변화나분자생물학적융합전사를검출하는 PCR이임상적인유용성을보이는 MRD 검출법으로알려져있다 [2-5]. 그러나유세포분석과 PCR 중어느것이 MRD 모니터링의일상검사법으로최적인가에대해서는아직확실한결론이없다. PCR (10-4 -10-6 ) 이유세포분석 (10-3 - 10-4 ) 보다좀더나은민감도를보이긴하지만, 일상검사로적용시고려해야할점즉, 검사소요시간, 검사의복잡성, 비용등에서어느한쪽이다른쪽을확고하게압도하지못하기때문이다 [4, 5]. 그러나유세포분석이 PCR보다신속하게결과를낼수있고, 임상적으로적용하기쉬우며비용이덜든다는것이일반적으로받아들여지는유세포분석의상대적인장점이다 [4, 5]. 항체조합의종류와수, 적용한 LAP의특질, 검체채집시기등이연구마다다양하므로임상적인의미를갖는 MRD의기준에대해일률적으로정의할수는없다. 지금까지의연구결과들을살펴보면항암치료기간이길수록예후적의미를갖는 MRD 의역치가낮아지는경향을보이기는하지만, 계열에상관없이 0.01% 에서 1.0% 까지의범위내에서제시되고있음을알수있다 [7, 8, 10-14, 16-18, 21, 22]. 본연구에서는이전보고에서 사용하였던기준과실제 MRD 결과의분포와분석의편의를고려하여높은 MRD의기준을 0.1%, 0.5%, 1.0% 로설정하였는데, 1.0% 를기준으로나누었을때가 0.5% 또는 0.1% 보다상대적으로유의한임상적분별력을나타내었다. 지금까지많은연구들을통해유세포분석을이용한 MRD 측정이급성백혈병의예후인자로인정받고있다. 소아 ALL 환자군에서는관해후 MRD 수준이강력하면서도독립적인예후인자로알려져있다 [6-12]. 195명의소아 ALL 환자를대상으로한연구에서는높은 MRD를보인환자들 ( 관해유도치료후 1% 이상또는지속적인치료 14주후 0.1% 이상 ) 이 MRD가검출되지않은환자들보다유의하게높은재발률을보였다 [7]. 최근 2,143명의소아 B세포 ALL 환자를대상으로세가지시점 ( 관해유도 8일, 29일, 공고요법후 ) 에서실시한유세포분석 MRD 의의의에대한연구결과가보고되었는데, 관해유도 8일과 29 일째측정한 MRD가예후적의미가있었다. 특히 29일째측정한 MRD가 0.01% 이상인경우다변량분석에서도다른어떤변수보다강력한예후인자이었다 [12]. 본연구의 ALL 환자군에서도, 통계학적으로유의하지는않았으나, 높은 MRD군에서낮은 MRD군보다높은재발률및짧은생존기간등불량한임상경과를보였다. AML 환자를대상으로한연구에서도관해후 MRD 정도와임상경과와의연관성이지속적으로보고되고있다 [13-22]. 53 명의 AML 환자를대상으로한초기연구에서관해유도후 MRD 가 0.5% 이상인환자들이 0.5% 미만인환자들보다유의하게높은재발률을보였다 [13]. 이후 56명의환자를대상으로한연구에서는공고요법후 MRD가 0.035% 이상인환자들이그미만인환자들보다유의하게높은재발률을보였고, 세포유전학적표준및불량예후군, MDR1 표현형, 짧은무재발생존및전체생존등과상관성을보였다 [14]. 72명의환자를대상으로한최근연구에서는백분율로표현된 MRD뿐아니라 ml당세포수로나타낸절대값도임상결과를예측할수있는표지자라고하였다 [21]. 본연구의 AML 환자군에서는높은 MRD군이낮은 MRD군보다상대적으로높은재발률및짧은생존기간을보였으나그차이가 ALL에비해작았다. 이러한결과의원인으로는
538 Korean J Lab Med 2010;30:533-9 적은대상수, 짧은추적기간, ALL에비해 AML 백혈병세포가보이는면역표현형의다양성등을생각할수있다. 본연구결과특기할만한사항은 AML 환자의경우높은 MRD군에서통계학적으로유의하게세포유전학적예후불량군의빈도가높고, 양호군의빈도가낮았다는것이다. 일반적으로치료전세포유전학적소견은급성백혈병환자의완전관해율, 완전관해유지기간, 그리고전체생존기간등을예측할수있는강력한예후인자로알려져있다 [25]. 그러나 AML과는달리 ALL 환자에서는 MRD군과세포유전학적예후군과의분포가연관성이없었다. 오히려세포유전학적예후양호군에서 1.0% 이상의높은 MRD의빈도가더높게분석되는양상을보였다. 이러한소견의원인으로는역시적은대상수와짧은추적기간등을들수있다. 하지만높은 MRD가측정된 ALL 환자에서불량한임상경과를보였다는점을고려하면, ALL에서는유세포분석에의한 MRD 측정이세포유전학적분류와는독립적으로작용하는예후인자일수도있다. 이에대해서는장기간전향적연구가필요할것으로생각된다. 본연구는유세포분석을통한 MRD 측정의임상적의의에대해국내에서처음으로기술한보고이고, 교차계열항원을표현한환자들만대상으로하여분석에사용한항원의수를최소화함으로써 MRD 측정에있어유세포분석의가용성을제시하였다. 본연구결과높은 MRD군에속한환자들이불량한임상경과를보이는경향이있었고, 이러한경향은 AML보다 ALL에서더두드러졌다. 향후국내에서도더많은기관에서유세포분석을이용한 MRD 측정에관한연구가이루어져측정방법, 검사시기, 항체조합등에대한표준화가이루어지고, 궁극적으로환자치료에직접적인도움이되길기대한다. 요약배경 : 급성백혈병의치료에있어유세포분석에의한미세잔존질환 (minimal residual disease, MRD) 측정은예후적의의를지니는것으로알려져있다. 이에저자들은국내에서는처음으로유세포분석을이용한 MRD 측정의의의를평가하고자하였다. 방법 : 교차계열항원을표현하는급성백혈병으로처음진단되었거나형태학적으로재발한환자 89명의완전관해당시의골수흡입검체를이용하여 MRD를측정하였다. MRD 빈도에따라 1.0% 이상은높은 MRD군으로, 1.0% 미만은낮은 MRD 군으로분류하였다. 결과 : 급성림프모구백혈병 (ALL) 환자는 47명이었고, 높은 MRD군은 10명, 낮은 MRD군은 37명이었다. 높은 MRD군에서낮은 MRD군보다재발빈도가높은경향을보였다 ( 각각 40.0% 와 13.5%, P=0.08). 무재발생존율및전체생존율은높은 MRD 군에서불량하였으나통계학적유의성이없었다. 급성골수성백혈병 (AML) 환자는 42명이었고, 높은 MRD군은 16명, 낮은 MRD군은 26명이었다. MRD의정도에따라재발률, 무재발생존율, 전체생존율은유의한차이를보이지않았으나높은 MRD 군에서통계학적으로유의하게세포유전학적예후불량군의빈도가높았고, 양호군의빈도는낮았다 (P=0.03). 결론 : 교차계열항원의유세포분석을이용한 MRD 측정은 AML보다 ALL 환자군에서치료경과예측에유용할수있을것으로생각된다. 향후국내에서도추가연구들을통해유세포분석의측정법, 측정시기, 항체조합등에대한표준화가이루어지길기대한다. 참고문헌 1. Vidriales MB, San-Miguel JF, Orfao A, Coustan-Smith E, Campana D. Minimal residual disease monitoring by flow cytometry. Best Pract Res Clin Haematol 2003;16:599-612. 2. Chung NG, Buxhofer-Ausch V, Radich JP. The detection and significance of minimal residual disease in acute and chronic leukemia. Tissue Antigens 2006;68:371-85. 3. Kern W, Haferlach C, Haferlach T, Schnittger S. Monitoring of minimal residual disease in acute myeloid leukemia. Cancer 2008;112: 4-16. 4. Campana D. Status of minimal residual disease testing in childhood haematological malignancies. Br J Haematol 2008;143:481-9. 5. Al-Mawali A, Gillis D, Lewis I. The role of multiparameter flow cytometry for detection of minimal residual disease in acute myeloid leukemia. Am J Clin Pathol 2009;131:16-26. 6. Ciudad J, San Miguel JF, Lopez-Berges MC, Vidriales B, Valverde B, Ocqueteau M, et al. Prognostic value of immunophenotypic detection of minimal residual disease in acute lymphoblastic leukemia. J Clin Oncol 1998;16:3774-81. 7. Coustan-Smith E, Sancho J, Hancock ML, Boyett JM, Behm FG, Raimondi SC, et al. Clinical importance of minimal residual disease in childhood acute lymphoblastic leukemia. Blood 2000;96:2691-6. 8. Coustan-Smith E, Sancho J, Behm FG, Hancock ML, Razzouk BI, Ribeiro RC, et al. Prognostic importance of measuring early clearance of leukemic cells by flow cytometry in childhood acute lym-
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