The prognosis and survival of childhood acute lymphoblastic leukemia with central nervous system relapse

Central nervous system (CNS) relapse in childhood acute lymphoblastic leukemia (ALL) has been overcome by sensitive therapeutic approachs. This study was planned to present the development of CNS relapse and survival in newly diagnosed 190 ALL patients whose cases were followed in the authors' unit between March 1991 and May 2002. St. Jude Study XI protocol was given to the patients who applied between March 1991 and March 1997 (group A) (n = 122), and St. Jude Study XIII protocol was given to the patients who applied between March 1997 and May 2002 (group B) (n = 68). The patients having isolated CNS relapse in group A received craniospinal irradiation (CSI) median 3.5 months after CNS relapse (range 2-6 months), a short time after reinduction, and 2 cures of consolidation. In group B, patients having isolated CNS relapse received IT once a month and a high-dose methotrexate treatment once every 8 weeks and 3 or 4, cures later therapy CSI median 7 months after CNS relapse (range 6-8 months) was given. When the overall survival rates of the 2 groups are compared, a statistically significant higher survival rate at 5 years was determined in group B than in group A (respectively, 82.3%, 58.4%) (p < .05). When subgroups of the patients (that is, those with no relapse, isolated CNS or BM relapse, or CNS + BM relapse) were compared in both groups, it was found that survival was much higher for the ones with no relapse and with isolated CNS relapse (respectively, 87.9%, 72.7%) compared to isolated BM or CNS + BM relapse groups (respectively, 10%, 13.3%) (p < .05). In a conclusion, for children with acute lymphoblastic leukemia and an isolated CNS relapse, with delayed definitive craniospinal irradiation allowing more intensive systemic and intrathecal chemotherapy results in better overall survival than has been previously reported.     

CXCR4在儿童急性白血病的表达及临床意义

目的探讨儿童急性白血病(AL)骨髓细胞表面CXCR4的表达及其临床意义。方法采用流式细胞术分别检测43例初诊未治急性白血病患儿(实验组)和10例非恶性血液病患儿(对照组)骨髓细胞表面CXCR4的表达情况。结果1.急性白血病患儿骨髓细胞表面CXCR4的相对荧光强度明显高于对照组(P<0.05)。2.ALL组CXCR4的相对荧光强度明显高于AML组(P<0.05)。3.髓外浸润组患儿初诊时CXCR4的相对荧光强度明显高于非髓外浸润组。(P<0.05)。4.实验组患儿CXCR4的相对荧光强度与外周血白细胞计数(WBC)呈正相关关系,相关系数为0.58(P<0.05)。结论1.CXCR4在儿童急性白血病初诊时为高水平表达,提示它可以作为急性白血病的一种检测指标。2.CXCR4的表达在ALL明显高于AML,说明它与急性白血病的类型具有一定相关性。3.急性白血病患儿骨髓细胞表面CXCR4的高表达与髓外浸润密切相关,并且和初诊时高白细胞计数有关。     

The Prognosis and Survival of Childhood Acute Lymphoblastic Leukemia with Central Nervous System Relapse

Central nervous system (CNS) relapse in childhood acute lymphoblastic leukemia (ALL) has been overcome by sensitive therapatic approachs. This study was planned to present the development of CNS relapse and survival in newly diagnosed 190 ALL patients whose cases were followed in the authors' unit between March 1991 and May 2002. St. Jude Study XI protocol was given to the patients who applied between March 1991 and March 1997 (group A) (n = 122), and St. Jude Study XIII protocol was given to the patients who applied between March 1997 and May 2002 (group B) (n = 68). The patients having isolated CNS relapse in group A received craniospinal irradiation (CSI) median 3.5 months after CNS relapse (range 2–6 months), a short time after reinduction, and 2 cures of consolidation. In group B, patients having isolated CNS relapse received IT once a month and a high-dose methotrexate treatment once every 8 weeks and 3 or 4, cures later therapy CSI median 7 months after CNS relapse (range 6–8 months) was given. When the overall survival rates of the 2 groups are compared, a statistically significant higher survival rate at 5 years was determined in group B than in group A (respectively, 82.3%, 58.4%) (p < .05). When subgroups of the patients (that is, those with no relapse, isolated CNS or BM relapse, or CNS + BM relapse) were compared in both groups, it was found that survival was much higher for the ones with no relapse and with isolated CNS relapse (respectively, 87.9%, 72.7%) compared to isolated BM or CNS + BM relapse groups (respectively, 10%, 13.3%) (p < .05). In a conclusion, for children with acute lymphoblastic leukemia and an isolated CNS relapse, with delayed definitive craniospinal irradiation allowing more intensive systemic and intrathecal chemotherapy results in better overall survival than has been previously reported.     

PART II. SURVIVAL AFTER RELAPSE DURING UNMAINTAINED REMISSION AND AFTER SECOND CESSATION OF THERAPY

Nygaard, R. and Moe, P. J. (Department of Paediatrics, University Hospital, Trondheim, Norway). Outcome after cessation of therapy in childhood leukemia. A population-based Nordic study of 986 patients. II. Survival after relapse during unmaintained remission and after second cessation of therapy. Acta Paediatr Scand Suppl 354: 20, 1989.
This is the second part of a population-based investigation of 986 patients after discontinuation of therapy for childhood leukemia. Patients who had their first relapse after cessation of therapy ( n =206) were studied for subsequent outcome in terms of survival after relapse. The patients with ALL ( n =191) were also analyzed according to patient variables with possible influence on survival. Fifty-one (26.7%) of the patients with relapse of ALL electively stopped therapy once more, and for them subsequent survival in remission was evaluated.
The overall estimated proportion alive at five years after relapse in unmaintained remission was 0.37 and at ten years 0.28. There was no significant difference in survival after relapse for males vs. females, and this could be attributed to the fact that isolated testicular relapses carried a better chance of subsequent survival than did relapses in other sites. Age at relapse did not have any influence on survival. However, time from cessation of therapy to first relapse was of prognostic value: Patients who relapsed within 6 months had a signifcantly lower survival than did those with relapse after longer periods in unmaintained remission.
Five-year DFS was 0.57 after second cessation of therapy in patients with ALL. Our study confirms that there may be more than one chance of cure.     

Initial response to therapy as an important prognostic factor in acute lymphoblastic leukemia in childhood. COALL study group

Prognostic factors to estimate the risk of relapse are crucial for risk-adapted therapy in acute lymphoblastic leukemia (ALL). In a cooperative multicenter treatment study for childhood ALL (COALL-03-85) the prognostic relevance of the bone marrow (BM) blast count at day 28 was evaluated. Treatment was adjusted to the initial risk factors; patients with high risk (white blood count (WBC) greater than or equal to 25/nl, age greater than or equal to 10 years, T- or NULL-ALL) received intensified therapy consisting of rotation of 6 non cross-resistant drug combinations with 12 different agents. After 4 weeks 289/305 (94.8%) children were in complete remission (CR); one child died of infection, and 15 (14 high-risk patients) still had more than 5% blasts in the BM. Twelve of these 15 patients were in remission after 2 to 4 weeks additional treatment. Poor responders often had a high initial WBC, age above 10 years of T- or NULL-ALL. In spite of continuation of intensive therapy all children with more than 10% blasts in the BM on day 28 suffered an early relapse except 2 who were transplanted in first remission. Event-free survival for the poor responders is 0.15 compared to 0.71 (p = 0.0001) for the good responders (median observation time 48 months). In multivariate analysis remission status on day 28 was the only significant prognostic factor in high-risk patients above one year of age; traditional risk factors as initial WBC, age above 10 years, hepatosplenomegaly, and immunological subtype were of no prognostic significance in this study. (ABSTRACT TRUNCATED AT 250 WORDS)     

Relapse after first cessation of therapy in childhood acute lymphoblastic leukemia: A 10-year follow-up study

The outcome of 171 children with ALL who relapsed for the first time after elective cessation of therapy (1–86 mo) and followed over 10 years (median 60 mo; range 1–232 mo) has been evaluated. One hundred and three patients relapsed in the bone marrow (BM), 29 in the testis (T), 21 in the central nervous system (CNS), 14 in the BM plus another site and 4 in other sites. Second remission was achieved in 97% of patients (97% BM, 100% T, 90% CNS, respectively) with reinduction schedules including three or more drugs. All but 4 out of 100 patients who relapsed in the BM received cranial reprophylaxis with intrathecal CT alone or CT plus radiotherapy. Seven patients in second CR underwent allogeneic bone marrow transplantation from an HLA matched sibling. The overall survival was 34% and disease-free survival (DFS) probability at 100 years was 22%. A second relapse was observed in 73% of patients. Forty children are alive in second continuous remission and 24 are alive after a second or subsequent relapse. Patients with isolated T relapse showed a significant better outcome than those with BM or CNS involvement. Most patients (62%) with isolated BM relapse showed a further disease recurrence in BM, and DFS was shorter when relapse occurred within 12 months from off-therapy. Eighty-two patients in second CR stopped the treatment a second time and showed a survival and DFS probabilities, respectively, of 69% and 43%. Thus, children with ALL who relapse after cessation of therapy still have a high risk of further late relapses and should be treated with intensive chemotherapy and CNS reprophylaxis. BMT must be considered for all patients relapsing in the BM within 12 months from off-therapy. © 1995 Wiley-Liss, Inc.     

儿童急性淋巴细胞白血病nm23-H1基因表达及其与免疫分型的关系

目的：探讨儿童急性淋巴细胞白血病(ALL) nm23-H1基因的表达水平及其与免疫分型的关系。方法：应用半定量逆转录-聚合酶链反应(RT-PCR)的方法检测儿童ALL初治、缓解、难治、复发患儿及正常对照儿童nm23-H1基因的表达水平,观察nm23-H1基因与免疫表型的关系。结果：①初治患儿nm23-H1表达水平明显高于正常对照组（P<0.01）和完全缓解组（P<0.01）;完全缓解组nm23-H1表达水平与对照组差异无显著性（P>0.05）,复发组nm23-H1表达水平高于正常对照组（P<0.01）和完全缓解组（P<0.01）,与初治差异无显著性(P>0.05);难治组均为高表达。 ②T-ALL的nm23-H1阳性率高于B-ALL(P<0.05),且T-ALL的nm23 H1表达水平高于B-ALL（P<0.05）。结论： nm23-H1的表达水平随儿童ALL的病情发展而变化,在初治、复发及难治ALL具有高表达,nm23-H1高表达者预后差,易复发;nm23-H1在T-ALL具有高表达,可能是T-ALL的缓解率低、预后差的原因之一。［中国当代儿科杂志,2009,11-11）：881-884］     

儿童急性淋巴细胞白血病nm23-H_1基因表达及其与免疫分型的关系

目的探讨儿童急性淋巴细胞白血病(ALL)nm23-H1基因的表达水平及其与免疫分型的关系。方法应用半定量逆转录-聚合酶链反应(RT-PCR)的方法检测儿童ALL初治、缓解、难治、复发患儿及正常对照儿童nm23-H1基因的表达水平,观察nm23-H1基因与免疫表型的关系。结果①初治患儿nm23-H1表达水平明显高于正常对照组(P<0.01)和完全缓解组(P<0.01);完全缓解组nm23-H1表达水平与对照组差异无显著性(P>0.05),复发组nm23-H1表达水平高于正常对照组(P<0.01)和完全缓解组(P<0.01),与初治差异无显著性(P>0.05);难治组均为高表达。②T-ALL的nm23-H1阳性率高于B-ALL(P<0.05),且T-ALL的nm23-H1表达水平高于B-ALL(P<0.05)。结论nm23-H1的表达水平随儿童ALL的病情发展而变化,在初治、复发及难治ALL具有高表达,nm23-H1高表达者预后差,易复发;nm23-H1在T-ALL具有高表达,可能是T-ALL的缓解率低、预后差的原因之一。     

The influence of traumatic lumbar puncture and timing of intrathecal therapy on outcome of pediatric acute lymphoblastic leukemia

The CNS is a frequent site of relapse of childhood acute lymphoblastic leukemia (ALL). Traumatic lumbar puncture (TLP) is thought to increase the risk of CNS relapse. The authors examined whether TLP at the time of diagnosis affected outcome and whether this effect was influenced by the timing of intrathecal therapy (IT) in 77 patients with newly diagnosed ALL. IT was instilled at the time of either the diagnostic LP (early) or a second LP 24-48 h later (delayed). Of the 19 patients who had a TLP at diagnosis and received late IT therapy, 6 had isolated CNS relapse and 2 had combined CNS and bone marrow (BM) relapse. Of the 9 patients who had TLP and received early IT therapy, 1 had a CNS relapse (p = .20). In an analysis stratified according to risk of relapse, the odds ratio (OR) for relapse was 0.8 among patients at low and standard risk who had delayed IT therapy after TLP (p = .99) vs. 0.17 for those who had early IT (p = .47). Importantly, among patients with high-risk ALL, the OR for relapse was 21.0 for delayed IT therapy (p = .09) and only 1.5 for early IT therapy after TLP (p = .99). The results indicate that TLP at diagnosis appears to increase the risk of CNS relapse markedly in patients with high-risk ALL, and the use of early IT therapy appears to reduce this risk. These findings need to be confirmed by prospective, randomized studies.     

The clinical value of follow-up examinations in childhood T-cell acute lymphoblastic leukemia and T-cell non-Hodgkin's lymphoma

BACKGROUND: The aim of this study was to evaluate the value of follow-up investigations of T-cell acute lymphoblastic leukemia (T-ALL) and T-cell non-Hodgkin's lymphoma (T-NHL), including cerebrospinal fluid (CSF) examination, bone marrow (BM) aspiration, peripheral blood (PB) count, serum lactate dehydrogenase (LDH) and chest X-rays in patients with an initial mediastinal enlargement. PROCEDURE: We reviewed clinical records of all T-ALL patients from 1987 to 2002 and all T-NHL patients from 1977 to 2002, seen at a single institution. RESULTS: Of 48 T-ALL patients, 15 suffered from a relapse, 6 (40%) were asymptomatic at the time of relapse. T-ALL (13/30) with mediastinal enlargement at first diagnosis relapsed versus 2/16 of those without mediastinal enlargement. However, at relapse, only one patient had a mediastinal mass, which in addition was symptomatic. Of 39 T-NHL patients, 6 patients relapsed. Forty percent of relapsed T-ALL and 17% of relapsed T-NHL were asymptomatic. The seven asymptomatic relapses were detected by CSF (n = 4), BM (n = 2) or blood count (n = 1) examinations. All T-ALL and T-NHL patients with a mediastinal relapse were symptomatic. CONCLUSIONS: This study suggests that routine CSF examinations during treatment can detect relapses of T-ALL and T-NHL before onset of symptoms, which might be of clinical value. Relapses are rarely detected by BM or blood examinations and whether this translates in a clinical benefit is unlikely. Routine chest X-rays are not useful.     

Outcome after relapse in an unselected cohort of children and adolescents with Ewing sarcoma

BACKGROUND: Survival after relapse in patients with Ewing sarcoma is very poor and this retrospective study attempts to identify of prognostic factors predicting survival after relapse. PROCEDURE: A total of 191 patients with localised Ewing sarcoma were registered in the ET-2 trial of the United Kingdom Children's Cancer Study Group (UKCCSG). All patients received standardised primary treatment with chemotherapy and surgery and or radiotherapy as local modality treatment. Sixty-four patients who relapsed are included in this report. Treatment at relapse was variable and included chemotherapy, surgery, radiotherapy and high dose therapy (HDT) or megatherapy with peripheral stem cell transplantation (PBSCT) or autologous bone marrow transplantation (ABMT) in various combinations. A subgroup of patients had only non-specific symptomatic treatment at relapse. Both univariate and multivariate methods were used to investigate variables affecting survival after relapse. RESULTS: The overall actuarial median survival from relapse for all patients was 14 months (95% CI 11-16 months). Univariate analysis showed that males had a longer survival (median, 16 months vs. 11 months); patients who relapsed while on treatment did worse (median, 3 months vs. 16 months) and patients who had a longer disease-free interval (DFI) prior to relapse had a better outcome (DFI <1 year, median survival = 3 months; DFI 1-2 years, survival = 8 months; DFI > 2 years, median survival = 24 months, P < 0.001). Multivariate analysis confirmed that duration of first remission was the only factor associated with longer survival after relapse. CONCLUSIONS: These data suggest that although aggressive therapy may delay disease progression after relapse for some children, the course of the disease after relapse is usually fatal. International co-operative studies are needed to evaluate new strategies.     

ALL-2005方案治疗儿童T系急性淋巴细胞白血病35例疗效总结

目的研究ALL-2005方案治疗儿童T系急性淋巴细胞白血病(T-ALL)的疗效。方法对2005年5月-2009年4月初发的35例T-ALL患儿采用ALL-2005方案进行分层治疗及疗效分析。结果 T-ALL患儿35例,男30例(86%),女5例(14%),发病时中位年龄8.3(2.0～15.6)岁。其中>10岁患儿14例,占40%。起病时外周血白细胞≥50×109/L者24例,占69%,起病时6例患儿有纵隔增宽。泼尼松治疗第8天时泼尼松试验反应好者22例(63%)。诱导治疗第35天有29例获完全缓解(83%),骨髓微小残留病(MRD)≤0.01%者共20例(67%)。治疗第55天时MRD≤0.01%共26例(87%)。4例复发,3例失访,6例死亡(包括3例复发和3例第1疗程未缓解而放弃治疗者)。随访至2011年6月31日,中位随访时间39(1～71)个月,5年无事件生存率为73.5%。结论 ALL-2005方案治疗儿童T-ALL疗效较好。     

白细胞介素-8及其受体在小儿急性白血病骨髓单个核细胞中的表达和临床意义

目的：探讨白细胞介素8(IL8)及受体(IL8R)在小儿急性白血病骨髓单个核细胞中的表达和临床意义。方法：RTPCR法检测32例急性白血病骨髓单个核细胞IL8,IL8RmRNA表达。结果：急性髓系白血病(AML)组中有5例表达IL8(5/10),4例表达IL8R(4/10);急性淋巴细胞白血病(ALL)组中有13例表达IL8(13/22),9例表达IL8R(9/22)。IL8在急性髓系白血病组中的表达水平高于急性淋巴细胞白血病组,差异有显著性(P<0.05)。AML组中M4M5亚型中的表达水平高于M2M3,差异有显著性(P<0.05)。ALL组中B系列ALL表达水平高于TALL,差异有显著性(P<0.05)。化疗后患儿骨髓单个核细胞IL8,IL8R水平显著低于化疗前(P<0.05)。结论：小儿急性白血病有IL8,IL8R的表达,IL8尤其在AML组M4M5亚型及B系列ALL更明显,化疗后两者水平显著下降。     

Allogeneic bone marrow transplantation versus chemotherapy in children with acute leukemia in Sweden

All children in Sweden who underwent bone marrow transplantation (BMT) with an HLA-identical sibling during a 5-year period were compared to those who were treated with chemotherapy and survived at least 3 months after remission. All patients were observed for more than 2 years after diagnosis or relapse. All 11 children with acute myeloid leukemia in first remission who underwent BMT survived compared to only 1 of 15 treated with chemotherapy (p less than 0.001). In children with acute lymphoblastic leukemia (ALL), those relapsing while on chemotherapy and treated with BMT in second to fourth remission (n = 16) had a 5-year survival of 43% compared to 16% for those treated with chemotherapy (n = 53, p less than 0.05). In children with ALL relapsing after cessation of therapy, 4-year survival was 33% for BMT (n = 6) and 55% for chemotherapy (n = 15), p = 0.05).     

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目的分析髓系抗原阳性儿童急性淋巴细胞白血病(ALL)的临床特点及预后关系。方法根据国际白血病欧洲协作组(EGIL)标准将1999—2004年上海交通大学医学院附属上海儿童医学中心收治的33例髓系抗原阳性表达的ALL(My+ALL)分为双表型、双系列型给予正规治疗。对其预后进行观察。结果(1)My+ALL患儿,双表型26例(78.8%,26/33),其中B系ALL伴髓系表达17例(65.4%,17/26),T系ALL伴髓系表达6例(23.1%,6/26),T系B系伴髓系表达3例(11.5%,3/26)。双系列ALL患儿7例(21.2%,7/33)。(2)26例双表型ALL患儿治疗35d,缓解率80.7%。7例双系列型ALL仅1例达缓解(14.3%)。(3)生存状态双表型26例中20例处于缓解状态(76.9%),双系列型7例中仅1例(14.3%)。(4)复发情况双表型6例复发(23.1%,6/26),双系列7例中6例复发(85.7%)。结论髓系抗原阳性表达在儿童ALL时不能作为预后不良的因素,但双系列白血病患儿预后差,复发率高,长期生存机会少。     

Immune mediators in idiopathic nephrotic syndrome: evidence for a relation between interleukin 8 and proteinuria

The pathogenesis of idiopathic nephrotic syndrome (INS) remains unknown. Several findings suggest a role for the immune system. This study aimed to evaluate immune mediators in INS by measuring plasma and urinary levels of transforming growth factor beta1 (TGF-beta1), monocyte chemoattractant protein-1 (MCP-1/CCL2), regulated on activation normal T-cell expressed and secreted (RANTES/CCL5) and IL-8 (IL-8/CXCL8) in pediatric patients with INS and in age-matched healthy controls. Patients were divided according to their response to corticosteroids: steroid-sensitive (SS, n = 8), or steroid-resistant (SR, n = 24). Immune mediators were also compared in regard with disease activity (relapse and remission). Immune mediators were measured by ELISA. Plasma TGF-beta1 levels in SR patients were approximately 2.8-fold higher than control values (p < 0.05). Urinary IL-8/CXCL8 was 2.9-fold higher in INS patients in relapse (proteinuria >100 mg/m2/24 h) when compared with patients in remission (p < 0.05), and levels had a positive correlation with individual proteinuria values (p < 0.05). Urinary IL-8/CXCL8 was significantly higher in relapsed SR than in SS patients in remission. No changes in MCP-1/CCL2 and RANTES/CCL5 levels were detected. Our findings suggest that IL-8/CXCL8 and TGF-beta1 are involved in the pathogenesis of INS: IL-8/CXCL8 associated with local changes in glomerular permeability and TGF-beta1 could be related to worse response to corticosteroids.     

Relapse in childhood acute lymphoblastic leukemia after elective cessation of initial treatment: Failure of subsequent treatment with cyclophosphamide,cytosine arabinoside,vincristine and prednisone (COAP)

Although the majority of children with acute lymphoblastic leukemia (ALL) can electively stop treatment after 21/2–5 years of continuous disease-free remission, 20–25% of those patients relapse after discontinuation of therapy. We treated 15 patients whose disease recurred after stopping treatment. Fourteen of them attained complete remission, but the median duration of disease-free survival was only 11 months. In this population, the site of initial relapse, bone marrow or testicle, did not influence subsequent outcome. Patients who relapsed within six months of stopping initial therapy had shorter second remissions than those who relapsed after six months. We conclude that the combination chemotherapy utilized in this study was inadequte for the control of relapsed ALL. Future programs will have to use different drug combinations or bone marrow transplantation.     

Allogeneic bone marrow transplantation in acute lymphoblastic leukemia of children. Analysis of prognostic factors. GEGMO (Bone Marrow Study Group) study

Sixty-five children with acute lymphoblastic leukemia (ALL) underwent allogenic bone marrow transplantation (BMT) from an HLA identical donor, following cytoreduction with cyclophosphamide and total body irradiation (TBI): 15 were transplanted in 1st remission, 43 in 2nd and 7 in 3rd or in 4th. The Kaplan Meier estimate of surviving disease free at 4 years post BMT was 49.9% and the probability of continued remission at 4 years was 63.3%. Fourteen patients relapsed between 90 and 690 days (mean: 240 +/- 88) post BMT. The other causes of BMP failure included: graft versus host disease, veno-occlusive disease and sepsis. No interstitial pneumonitis has been reported. Patients who had a relapse while on chemotherapy had a higher probability of relapse than those who had a relapse while off therapy (p less than 0.01). We conclude that allogeneic BMT is the treatment of choice for children with ALL in second hematologic remission, the interval between diagnosis and first relapse being the most significant prognostic factor. Patients with poor prognosis might benefit from a more intensive chemotherapy/total body irradiation schedule or a BMT earlier in the course of their disease.     

Relapse factors during maintenance therapy of acute lymphoblastic leukemia in children.

A statistical analysis of possible risk factors for relapse during maintenance therapy (MT) for acute lymphoblastic leukemia (ALL) has been performed. The patient material consists of 64 patients. Twenty-six patients were classified as standard risk (SR), 21 as intermediate risk (IR), and 17 as high-risk (HR) patients. Seventeen patients relapsed and 50 patients (78%) are alive at a median observation period of 86 months (range 39-146 months). Mean white blood cell count (mean WBC) based on weekly determinations, duration of treatment interruption, and the number of infectious episodes were calculated in each patient during the first 6 months of MT. In analyses starting at 6 months after the beginning of MT, these factors were related to relapse risk, time to relapse, and time to infection. Using the median WBC value (3.9 x 10(9)/L) of all patients during the first 6 months as a cutoff point, 14 patients with levels higher, and 3 patients with levels lower relapsed (p = .0004). Adjustment of mean WBC for leukemia risk groups had no influence on the analysis. Time to relapse was related to duration of interruption of MT (p less than .01). Time to relapse was not related to leukemia risk groups. Infection frequency was higher in HR patients compared to SR and IR risk patients (p = .04). As WBC level had a prognostic value and was previously shown to be related to 6-mercaptopurine (6-MP) peak plasma concentration, monitoring 6-MP plasma levels during MT could be helpful for optimizing treatment.