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AIMS--To assess the prevalence and degree of periodic acid Schiff (PAS) positivity in blast cells from children with lymphoblastic leukaemia (ALL); its association with other disease characteristics; and its clinical importance in predicting the outcome of treatment. METHODS--Marrow slides from entrants to a large United Kingdom multicentre ALL trial (UKALL X) were batch processed and assessed blind for PAS positivity by one morphologist. Patients were classified into groups A, B, and C, corresponding to less than 1% PAS positive cells, 1-10%, and over 10%, respectively. Their PAS pattern was then compared with other clinical and pathological features of ALL and with treatment outcome. RESULTS--Slides from 921 children were examined of which 371 (40%) were categorised as group A, 324 (35%) as group B, and 226 (25%) as group C. There was a clear association between the presence of blast cell vacuoles on Romanowsky staining and PAS positivity. Group A (PAS negative) patients included a disproportionate excess of those with L2 morphology, those under 2 or over 6 years of age, those with an initial white cell count over 50 x 10(9)/l, those with a T or null cell immunophenotype, and those with chromosomal abnormalities other than "high hyperdiploidy". Four years from diagnosis, group C patients had an 8% disease free survival advantage over those in group A (2p = 0.01). This was irrespective of initial white cell count, but not of immunophenotype or the presence of vacuoles. CONCLUSIONS--Strong PAS positivity is a feature of "common" ALL and is particularly associated with blast cell vacuoles. It does occasionally occur in other disease subtypes with or without vacuoles. It predicts a better response to current treatment, but not independently of other cell characteristics.

The UK MRC ALL97 trial included a randomised comparison of the efficacy and toxicity of dexamethasone and thioguanine (TG, experimental arms) with prednisolone and mercaptopurine (MP). The cytotoxic effects of MP and TG are mediated, in part, by thioguanine nucleotide (TGN) metabolites. TGNs are formed directly from TG whereas MP produces intermediate metabolites which are substrates for the enzyme thiopurine methyltransferase (TPMT). TPMT is under the control of a common genetic polymorphism. Both drugs are good substrates for TPMT. Both drugs undergo oxidative metabolism, but TG requires prior deamination. Consecutive children with ALL, diagnosed in the United Kingdom and Ireland between April 1997 and June 2002, were randomised to receive either TG or MP in maintenance courses. All patients received TG in intensification courses. Toxicity data was collected by an adverse event reporting system with follow-up questionnaires to seek detailed information on specific toxicities. Red blood cell (RBC) TGN concentrations and TPMT activities were measured by standard techniques in specific sub-groups. Of 1498 randomised patients, 750 were allocated TG and 748 MP. The trial produced a 5 year event-free survival (EFS) of 80%, with no difference in EFS or overall survival between thiopurine arms. However, TG was associated with an acute hepatitis syndrome with features of veno-occlusive disease (VOD) in 95 patients. Eighty-two of these were in the randomised TG arm (11% of TG recipients), the remaining were patients allocated MP who developed VOD during TG intensification courses. On long term follow-up, 43 (5.7%) TG recipients developed persistent splenomegaly and mild to moderate thrombocytopenia due to portal hypertension. TPMT activities were measured in 73 of the 95 VOD children at a standard protocol dose of thiopurine. For comparison, TPMT activities were measured in children who did not develop VOD or splenomegaly; there was no difference in the range of TPMT activities measured at 40mg/m2 TG (n = 83, median 15.4 units/ml RBCs) compared to 75mg/m2 MP (n = 78, median 15.2 units). Median TPMT activities in these 161 children, taking thiopurines at the protocol standard dose, were 15.2 units (range 5.8 to 23) compared to a median of 13.4 units (range 5.8 to 23) in the 73 VOD children (median difference 1.8 units, 95% CI 0.9 to 2.7, p < 0.001). A similar difference in TPMT activity was also seen when comparing persistent splenomegaly cases with controls. There was no difference in accumulation of TGNs at comparable doses. When used for maintenance therapy, TG causes liver toxicity in a significant minority of children with ALL without improving long term survival. An association with polymorphic variations in TPMT levels, a critical enzyme in thiopurine metabolism, implicates inter-individual variations in metabolism of the drug as a mechanism for liver damage, and points to a possible means of identifying at-risk patients. MP should remain the standard thiopurine for maintenance therapy unless longer follow-up reveals a survival advantage in favour of TG, and the mechanisms of liver toxicity are understood to avoid exposure of at risk patients.

As part of the Medical Research Council Leukaemia Trial UKALL VIII, 738 unselected children with acute lymphoblastic leukaemia (ALL) had the morphology of their marrow blast cells reviewed by a panel of three haematologists. Ninety four (13%) showed appearances classifiable as type L2 by the French American and British (FAB) cooperative group's criteria, five (0.7%) were typed L3, and the remaining 639 (86%) as L1. Disregarding the patients classified as L3, those with the L2 variant showed an inferior disease free survival to that of the remainder (p less than 0.01), and more of them failed to remit after receiving "standard" remission induction treatment (p less than 0.01). They included an excess of older children (p less than 0.01) with less profound marrow failure at diagnosis, and fewer of them expressed the common ALL antigen (p = 0.05). There was no association between L2 morphology and the diagnostic white cell count, sex, or the presence of a mediastinal mass. These findings confirm earlier reports that FAB L2 ALL is associated with a poor prognosis and that it occurs more commonly in older children. The high remission failure rate is a recent observation and indicates that alternative early treatment may be appropriate for such patients.

Aims Inherited differences in thiopurine methyltransferase (TPMT) activity are an important factor in the wide interindividual variations observed in the clinical response to thiopurine chemotherapy. The aim of this study was to establish a population range for red blood cell (RBC) TPMT activity in children with acute lymphoblastic leukaemia (ALL) at disease diagnosis. An additional aim was to investigate factors that can influence TPMT activity within the RBC. Methods Blood samples were collected from children with ALL at disease diagnosis, prior to any blood transfusions, as part of the nationwide UK MRC ALL97 therapeutic trial. RBC TPMT activity was measured by h.p.l.c. RBCs were age-fractionated on Percoll density gradients. Results Pretreatment blood samples were received from 570 children within 3 days of venepuncture. TPMT activities at disease diagnosis ranged from 1.6 to 23.6 units/ml RBCs (median 7.9) compared with 0.654–18.8 units (median 12.9), in 111 healthy control children (median difference 4.5 units, 95% CI 3.9, 5.1 units, P

Aims Since relatively little is known about the pharmacokinetics of 6-thioguanine (6TG) in children receiving 6-thioguanine for maintenance therapy of acute lymphoblastic leukaemia (ALL), we studied plasma drug concentrations under standardized conditions and investigated the effect of food on parent drug pharmacokinetics and the accumulation of the active metabolites 6-thioguanine nucleotides (6-TGNs) in red cells. Methods Single oral doses of 40 mg of 6-TG were administered both in the fasting and fed state to children with ALL. Pharmacokinetic sampling was performed up to 6 h post dose. Daily oral doses of 40 mg m−2 of 6-TG were administered both fasting and after food over two 4 week periods. Twice weekly samples were taken for metabolite concentrations. The study design was cross-over with each child receiving dosing in either fasted or after food over a 4 week period in each phase. Results Eleven patients were studied. A wide interindividual variation in Cmax (median 313 pmol ml−1, range 51–737) and AUC (median 586 pmol ml−1 h, range 156–1306) was observed in the fasted state. Concomitant food administration resulted in a significant reduction in Cmax (median 71 vs 313 pmol ml−1, P = 0.006, CI from 36 to 426), AUC (median 200 vs 586 pmol ml−1 h, P = 0.006, 95% CI from 109 to 692), and time to reach Cmax (median 1.5 vs 3 h, P = 0.013, 95% CI from 0.74 to 2.73). There was no difference in the steady state concentration of red cell 6-TGNs observed after a 4 week period of 6-TG administered fasting or after food. Conclusions Children with ALL demonstrate significant interindividual variation in 6-TG pharmacokinetics. Although there would appear to be a reduction in parent drug Cmax and AUC with food there was no difference in 6-TGN concentrations after 4 weeks of 6-TG. Taking the drug on an empty stomach may not be necessary.

Treatment of children with acute lymphoblastic leukaemia (ALL) aims to cure all patients with as little toxicity as possible and, if possible, to restrict further intensification of chemotherapy to patients with an increased risk of relapse. However in Medical Research Council (MRC) trial UKALL X two short myeloablative blocks of intensification therapy given at weeks 5 and 20 were of benefit to children in all risk groups. The successor trials, MRC UKALL XI and MRC ALL97, tested whether further intensification would continue to benefit all patients by randomising them to receive, or not, an extended third intensification block at week 35. After a median follow-up of 4 years (range 5 months to 8 years), 5 year projected event-free survival was superior at 68% for the 894 patients allocated a third intensification compared with 60% for the 887 patients who did not receive one (odds ratio 0.75, 95% CI 0.63–0.90, 2P = 0.002). This difference was almost entirely due to a reduced incidence of bone marrow relapses in the third intensification arm (140 of 891 in the third intensification arm vs 171 of 883 in the no third intensification, 2P = 0.02). Subgroup analysis suggests benefit of the third intensification for all risk categories. Overall survival to date is no different in the two arms, indicating that a greater proportion of those not receiving a third intensification arm and subsequently relapsing can be salvaged. These results indicate that there is benefit of additional intensification for all risk subgroups of childhood ALL.

As a prelude to a nationwide randomized trial of thioguanine (TG) versus mercaptopurine (MP) for childhood lymphoblastic leukaemia we compared a pilot group of 23 children taking TG with a matched group taking MP. We assessed drug tolerance based on haematological toxicity and measured erythrocyte (RBC) concentrations of thioguanine nucleotides (TGN). The median tolerated dose of TG was 30 mg/m2 compared to 55 mg/m2 for MP. There was no difference in the pattern of anaemia or neutropenia between the two groups, but dose-limiting thrombocytopenia was more evident in the TG children (P< 0.001), four of whom had a decrease in platelet count to

The relationship between the prescribed dose of drugs during continuing (maintenance) therapy, the degree of marrow suppression caused, and subsequent event-free survival was examined in a cohort of 740 children with lymphoblastic leukaemia treated on MRC UKALL X. Girls, younger children, and patients who had received intensification treatment, were prescribed lower doses of mercaptopurine, became neutropenic more readily, and had more interruptions of treatment. Children who had one or more episodes of neutropenia with a count of

At the commencement of UKALL XI, a national MRC trial for childhood lymphoblastic leukaemia (ALL), the therapy included a bolus of daunorubicin (DR) on the first 2 d of the protocol. This component of treatment was subsequently withdrawn because of concern about long-term cardiotoxicity. All children both before and after this change of policy had their marrow status at the end of the first week assessed by central review as part of the trial to examine the clinical importance of the rate of disease clearance. This also afforded an opportunity to observe the effect of DR on gross residual disease at an early stage of therapy. 1419 children were studied: 342 received DR (‘recipients’), 1077 did not. 44% of the recipients completely cleared their marrow of blast cells after 8 d compared with 13% of the non-recipients (χ2=158.2, P 80% blasts) was less impressive but there was still a difference in favour of DR recipients (DR 9%, no DR 15%; χ2=7.7, P=0.006). The rate of disease clearance correlated with disease-free survival for both recipients and non-recipients, but there was no significant difference in outcome when comparing the two groups with each other, either in terms of disease-free or relapse-free survival. DR accelerated the rate of blast cell disappearance from the marrow but the difference this made to disease free survival is small or non-existent. It appears to be the relative speed of response to a given therapeutic regimen that is prognostically important rather than the absolute rate of response when comparing one treatment with another.

The outcome in childhood leukaemia has shown steady improvement over the last decade and efforts are now concentrated on the stratification of patients by risk factors which may avoid overtreatment of good risk patients and limit dose escalation strategies, including those with bone marrow transplantation, to the higher risk patients. In ALL, risk stratification is based on the presenting white cell count, sex, age and cytogenetics of the tumour cells. Even in acute myeloid leukaemia, the outcome with chemotherapy alone is now sufficient to limit elective allogeneic bone marrow transplantation to those who do not have cytogenetically favourable disease. In non-Hodgkins lymphoma, a dramatic improvement in overall survival from 50% to in excess of 80% has been achieved by an escalation in dose and dose intensity of chemotherapy. With this improvement, the prognostic influence of clinical staging has become less clear and recent efforts have concentrated on determining which groups of patients would be cured by less intensive treatment. As for ALL, there is concern about the potential late sequelae in these highly curable children. There remain groups of unusual tumour types, such as anaplastic large cell and peripheral T cell lymphoma, where there remains much to be learned about the pathogenesis and clinical behaviour. The optimum treatment strategy for these subgroups remains to be clarified.

1. Red blood cells from four children with lymphoblastic leukemia were age fractionated on Percoll density gradients into 'young', 'middle-aged' and 'old' cells. 2. The rates of accumulation of the mercaptopurine (MP) metabolites thioguanine nucleotides (TGNs) and methylmercaptopurine nucleotides (MeMPs) were measured in the cell fractions from the start of MP continuing chemotherapy. 3. TGNs and MeMP metabolites were present in all the red cell fractions after 3 days oral MP. There was no significant difference between the metabolite concentrations measured in either young, middle-aged or old cells (Mann-Whitney P = 1.0 to 0.12). 4. These observations suggest that MP metabolites do not enter red cells at the stem cell level at the start of therapy. 5. With respect to the monitoring of therapy, these results suggest that the concentration of TGNs after 7 to 10 days MP could be used to predict eventual steady-state concentrations using a simple model.

Early studies indicated that low immunoglobulin (Ig) concentrations at diagnosis predict a worse outlook for children with acute lymphoblastic leukemia (ALL). We re-examined this suggestion in the light of immunophenotypic disease subtyping and more modern therapy. The concentrations of Ig, IgA, and IgM at diagnosis of ALL in 199 children were reviewed. One hundred forty-one (71%) had normal values and 58 (29%) had at least one abnormal value. No obvious pattern of abnormality relating to disease immunophenotype emerged. Disease-free survival (DFS) was not significantly different when simply comparing children with normal and abnormal values. Those with a white blood cell count lower than 20 x 10(9)/L (n = 106) included 22 with at least one low Ig whose 5-year DFS was inferior to the "normal" group (56% vs 83%; P0.005). The 140 children with CD10 + B precursor ALL included 31 with one or more low Ig concentrations who also showed an inferior 5-year DFS to the remainder (55% vs 77%; P0.02). Minor abnormalities in Ig concentrations are seen in approximately one third of children with ALL regardless of immunologic subtype. Low values may relate to poor outcome in patients with the disease at otherwise good risk.

AIMS--To evaluate the reliability of fluorescence in situ hybridisation (FISH) in the retrospective cytogenetic assessment of old bone marrow smears stored for periods of up to 20 years. METHODS--A series of bone marrow smears either Romanowsky stained, or frozen and unstained, and aged from one month to 20 years were hybridised with biotin labelled probes specific for the centromeric regions of human chromosomes X, 6, and 18. Sites of hybridisation were detected with fluoresceinated avidin. One hundred to 400 cells from each preparation were examined and the number of signals observed was recorded. RESULTS--All smears exhibited signals in most cells examined. In cytogenetically normal cases, an average 67.6% of cells (range 36%-90%) demonstrated the appropriate number of X centromere signals. In those samples known to contain extra chromosomes X, 6, or 18 the presence of cells with the abnormal copy number was clearly detected in each case. CONCLUSION--When applied in the way described, FISH can give consistent and accurate results with a variety of archival bone marrow smears, including aged prestained material. This will permit retrospective assessment of specific cytogenetic abnormalities in patients with leukaemia using their initial diagnostic slides even where these are several years old.

1. 6-Mercaptopurine (6-MP) is used in the continuing chemotherapy of childhood acute lymphoblastic leukaemia. The formation of red blood cell (RBC) 6-thioguanine nucleotide (6-TGN) active metabolites, not the dose of 6-MP, is related to cytotoxicity and prognosis. But there is an apparent sex difference in 6-MP metabolism. Boys require more 6-MP than girls to produce the same range of 6-TGN concentrations. Given the same dose, they experience fewer dose reductions because of cytotoxicity, and have a higher relapse rate. 2. The enzyme hypoxanthine phosphoribosyltransferase (HPRT) catalyses the initial activation step in the metabolism of 6-MP to 6-TGNs, a step that requires endogenous phosphoribosyl pyrophosphate (PRPP) as a cosubstrate. Both HPRT and the enzyme responsible for the formation of PRPP are X-linked. 3. RBC HPRT activity was measured in two populations, 86 control children and 63 children with acute lymphoblastic leukaemia. 6-MP was used as the substrate and the formation of the nucleotide product, 6-thioinosinic acid (TIA) was measured. RBC 6-TGN concentrations were measured in the leukaemic children at a standard dose of 6-MP. 4. There was a 1.3 to 1.7 fold range in HPRT activity when measured under optimal conditions. The leukaemic children had significantly higher HPRT activities than the controls (median difference 4.2 micromol TIA ml(-1) RBCs h(-1), 95% C.I. 3.7 to 4.7, P < 0.0001). In the leukaemic children HPRT activity (range 20.4 to 26.6 micromol TIA ml(-1) RBCs h(-1), median 23.6) was not related to the production of 6-TGNs (range 60 to 1,024 pmol 8 x 10(-8) RBCs, median 323). RBC HPRT was present at a high activity even in those children with low 6-TGN concentrations. 5. When HPRT is measured under optimal conditions it does not appear to be the metabolic step responsible for the observed sex difference in 6-MP metabolism. This may be because RBC HPRT activity is not representative of other tissues but it could equally be because other sex-linked factors are influencing substrate availability.

Blast cell morphology of children with lymphoblastic leukaemia (ALL) entering two national multicentre trials was prospectively reviewed by three haematologists to define the clinical importance of (a) French–American–British (FAB) classification, (b) the presence of cytoplasmic vacuoles, and (c) the presence of ‘hand-mirror’cells. Of 2135 evaluable children, 1907 (89%) had FAB L1 morphology and 228 (11%) L2. (L3 patients were not eligible for the trials in question). L2 patients more frequently had residual disease 14 d after starting treatment and had a significantly inferior disease-free survival, but not if the analysis was stratified for age, sex and diagnostic white cell count (WBC), 627 (29%) had blast cells with cytoplasmic vacuoles, and showed a significant survival advantage over the remainder. Vacuoles were positively associated with a low WBC, age range 1–6 years and blast cell positivity for CD10, but their benign influence was apparent even when these variables were taken into account. ‘Hand-mirror’(HM) cells were only studied in UKALL X, and were noted in 316/1402 (23%) children. There appeared to be an inverse correlation between HM cells and cytoplasmic vacuoles and a weak association with T-cell immunophenotype, but no prognostic significance was evident. FAB classification appears to be of less prognostic importance than has previously been supposed, though L2 disease is more resistant to current remission induction regimens. Hand-mirror cells may be more common in T-ALL, but are seen in all types and are not related to prognosis. Cytoplasmic vacuoles are predictive of a good response to current therapeutic schedules even allowing for other prognostic variables, and are the single most important morphological feature relating to prognosis in childhood ALL.

Summary During the 1970s, despite apparently similar treatment, the prognosis for children with lymphoblastic leukaemia (ALL) improved more in some countries, notably the United States and West Germany, than in others. To find out why, the first phase of the United Kingdom (UK) Medical Research Council (MRC) childhood ALL trial, UKALL VIII, was designed to see whether similar results to the United States Children's Cancer Study Group (CCSG) could be obtained in the U.K. using an identical protocol (CCG 162). Protocol 162 was one of a series of regimens devised by the American Children's Cancer Study Group in the 1970s and was used specifically for their average risk patients (all children with ALL with an initial white cell count up to 50 × 109/l except those aged 3–6 years with white cell counts under 10 × 109/l). One arm (1A) of their study was adopted by the MRC for all children in the U.K. aged 0–14 years with confirmed ALL. Eight hundred and twenty-nine consecutive patients were entered between 1980 and 1984. The first 199 patients formed a single arm study as per the original protocol 162 (arm 1A), but the subsequent 630 children were randomized to receive or not two doses of daunorubicin on the first 2 d of induction. This randomization was an attempt to answer the important question as to whether event-free survival was influenced by the use of four rather than three induction agents. A second randomization between 2 and 3 years continuing therapy was also introduced at this stage as it had been by the CCSG in their protocol. With a minimum follow up period of more than 5 years, disease-free survival for the whole group is 55%, a considerable improvement on all previous UKALL trials. Results for patients directly comparable with those in CCSG 162 (‘average risk’patients) and their American counterparts were similar. Daunorubicin was associated with more early deaths but improved disease-free survival for those achieving remission. More children relapsed who stopped treatment after 2 years than those who continued for 3, but this was balanced by increased treatment mortality in the third year. The fact that for UKALL VIII the results were similar to those of the CCSG suggests that previous MRC protocols were not sufficiently sustained and intensive, particularly during the maintenance phase of treatment. Daunorubicin may have provided better disease control, albeit with increased toxicity, and 3 years of maintenance therapy did not confer any advantage in long-term survival over 2 even though it may have reduced the rate of early relapse.

To explore the possibility that higher total dosage of 'maintenance' treatment may have contributed to the recent improvement in outlook of children in the United Kingdom with lymphoblastic leukaemia, details of the amount of 6-mercaptopurine prescribed during the first two years of treatment were studied in an unselected cohort of children diagnosed between 1973 and 1987. Eighty five patients were studied, 30 diagnosed before and 55 after 1980. The group diagnosed after 1980 showed an 18% improvement in relapse free survival at five years. Their median total dose of 6-mercaptopurine had increased by 22%, whereas according to the protocol it should have risen by an average of only 9%. After 1980 boys were prescribed significantly more 6-mercaptopurine than girls, and had fewer dose reductions because of myelosuppression. These findings support the clinical impression that after 1980 an important therapeutic difference resulting from the new United Kingdom acute lymphoblastic leukaemia protocols was an increase in the amount of 6-mercaptopurine that children actually received as a result of changes in prescribing guidelines rather than dose. They also provide further evidence that boys tolerate 6-mercaptopurine better than girls, which may be related to the still unexplained difference in prognosis between the sexes.

To define further the clinical importance of cytogenetic analysis in acute lymphoblastic leukaemia (ALL) a prospective study was performed on 139 unselected children. Analyses were considered adequate in 104, of whom 35 were normal and 69 had clonal abnormalities. Abnormalities were categorised according to banded chromosome analysis as well as chromosome count. Karyotypes were correlated with clinical and laboratory features at diagnosis and with survival. Of the successful analyses, thirty five (34%) children had no abnormalities; this group contained an excess of T cell disease. Twenty five (24%) had a "characteristic" hyperdiploid karyotype and as a group had lower presenting white counts, a tendency to CD10, and periodic acid schiff positivity of the blast cells and smaller spleens. None was an infant and only one was over 10 years old. Seven (7%) children with t(9; 22), t(8; 14), or t(4; 11) translocations were grouped together as "specific" translocations. Collectively they had a significantly worse prognosis than the remainder. Nine children developed central nervous system relapse, six of whom had either t(4; 11) or abnormalities of 9p or 19p. A descriptive classification taking into account chromosome bonding pattern is cytogenetically more appropriate and may be more clinically useful than grouping children simply by chromosome number. As knowledge and techniques improve, the classification of cytogenetic abnormalities in ALL will need to be kept under frequent review.

The current U.K. trial protocol (UKALL XI) for childhood lymphoblastic leukaemia demands mercaptopurine (MP) dose escalation in children who tolerate daily 75 mg/m2 MP (100% dose) without cytopenias. The previous trial (UKALL X) did not. MP metabolism was studied in a group of UKALL XI children (n = 21) who tolerated 100% dosages and who were matched in this respect with a similar group of UKALL X children. Red blood cell MP derived thioguanine nucleotide (TGN) concentrations were measured in both groups under comparable conditions; at 75 mg/m2 MP there was no significant difference. MP dose escalation in the UKALL XI children produced higher TGN concentrations (TGNs at 100% vs 125% dosages, median difference 90 pmol/8 x 10(8) RBCs, 95% CI 25 to 165 pmol, P < 0.02). Assayed at the time of cytopenia induced dose reduction, the UKALL XI children had accumulated significantly higher TGN concentrations than the UKALL X children (median difference 78 pmol/8 x 10(8) RBCs, 95% CI 20 to 144, P < 0.02). These findings indicate that dose escalation in children tolerant of 100% MP dosages produces higher peak TGN concentrations.

Transmission of hepatitis C virus (HCV) is an important hazard of blood transfusion and may result in chronic liver disease. 98 children from Nottingham and Sheffield with haematological malignancies were studied to determine the prevalence of HCV infection by enzyme immunoassay and RT/PCR techniques. The children had been exposed to up to 184 donors through red cell and platelet transfusion, the majority prior to routine testing for HCV infection in blood donors. Only one sample showed evidence of HCV infection being both ELISA and RT/PCR positive. None of the samples taken since donor screening were positive. This provides reassurance as to the low rate of HCV acquisition in multi-transfused patients in this part of the U.K. compared to other parts of the world.

A UK survey was carried out to discover the frequency, circumstances, and outcome of intracranial haemorrhage (ICH) complicating idiopathic thrombocytopenic purpura (ITP) of childhood. A questionnaire was circulated through the membership of the UK Paediatric Haematology Forum, and thence to local paediatricians and haematologists. It sought information on any child with ITP who had had an ICH during the 20 year period to January 1994. Fourteen instances were discovered, seven before 1984 and seven after. Six children survived the event with minimal or no sequelae, four without craniotomy. An immediately precipitating cause was noted in four; two had arteriovenous malformations and two suffered head injuries. The event occurred over two weeks from diagnosis in seven cases and over two months in five. All children were profoundly thrombocytopenic at the time of their intracranial bleed. By calculation the 14 children would have represented some 0.1% of the total with ITP during the period under review. ICH in childhood ITP may have a precipitating cause and is not necessarily fatal. There is no period of maximum risk, and it can occur at any time during the course of the illness when the platelet count is less than 10-15 x 10(9)/l. It is an extremely rare event and previous estimates of its incidence may have been too high.

To estimate the incidence and causes of secondary thrombocytosis in children, a 12 month study of all patients attending a children's hospital and discovered to have a platelet count over two times the upper normal limit (> 800 x 10(9)/l) was undertaken. Data so obtained were analysed both separately and together with those from two previous studies to gain as broad a perspective as possible. Of 7916 children who had platelet counts during the study period, 36 (0.5%) produced a value > 800 x 10(9)/l; there were 19 boys and 17 girls. There was a preponderance of young infants (median age 13 months). Twenty seven of the 36 had some sort of associated infection, bacterial in 18 and viral in nine. The other nine were either recovering from anti-neoplastic chemotherapy (n = 6), were post-operative (n = 2), or simply iron deficient (n = 1). Combining these patients with those described in previous studies allowed a review of 139 unselected children with very high platelet counts. Fifty three (38%) had infections, 29 (20%) had traumatic or surgical tissue damage, 16 (11%) had malignant disease undergoing chemotherapy or surgery, and 13 (9%) had connective tissue or autoimmune disorders. Secondary thrombocytosis is not rare and is most frequently seen in very young infants after infection. It can arise in a wide variety of other circumstances including rebound from myelosuppression, iron lack, or as part of an acute phase response. It is clinically unimportant in terms of morbidity and requires no treatment other than that for the primary condition.

Since relatively little is known about the pharmacokinetics of 6-thioguanine (6TG) in children receiving 6-thioguanine for maintenance therapy of acute lymphoblastic leukaemia (ALL), we studied plasma drug concentrations under standardized conditions and investigated the effect of food on parent drug pharmacokinetics and the accumulation of the active metabolites 6-thioguanine nucleotides (6-TGNs) in red cells.Single oral doses of 40 mg of 6-TG were administered both in the fasting and fed state to children with ALL. Pharmacokinetic sampling was performed up to 6 h post dose. Daily oral doses of 40 mg m(-2) of 6-TG were administered both fasting and after food over two 4 week periods. Twice weekly samples were taken for metabolite concentrations. The study design was cross-over with each child receiving dosing in either fasted or after food over a 4 week period in each phase.Eleven patients were studied. A wide interindividual variation in Cmax (median 313 pmol ml(-1), range 51-737) and AUC (median 586 pmol ml(-1) h, range 156-1306) was observed in the fasted state. Concomitant food administration resulted in a significant reduction in Cmax (median 71 vs 313 pmol ml(-1), P = 0.006, CI from 36 to 426), AUC (median 200 vs 586 pmol ml(-1) h, P = 0.006, 95% CI from 109 to 692), and time to reach Cmax (median 1.5 vs 3 h, P = 0.013, 95% CI from 0.74 to 2.73). There was no difference in the steady state concentration of red cell 6-TGNs observed after a 4 week period of 6-TG administered fasting or after food.Children with ALL demonstrate significant interindividual variation in 6-TG pharmacokinetics. Although there would appear to be a reduction in parent drug Cmax and AUC with food there was no difference in 6-TGN concentrations after 4 weeks of 6-TG. Taking the drug on an empty stomach may not be necessary.

Results of three consecutive completed UK trials (1980-1997) for childhood lymphoblastic leukaemia are presented. National accrual has progressively increased so that over 90% of all the country's ALL cases were treated on the latest trial reported, UKALLXI. From 1980 to 1990, event-free and overall survival progressively improved, following adoption of an American therapy template and use of two post-remission intensification modules. Since 1990 despite demonstration of the benefit of a third intensification module overall event-free survival (EFS) has not improved further. Survival remains high due to a good retrieval rate especially for those relapsing off treatment after receipt of two intensification pulses. Possible reasons for the plateau in event-free survival (including type and dose of induction steroid, dropping of induction anthracycline, type and dose of asparaginase, gaps early in therapy following intensification, and overall lack of compliance in maintenance) are being explored in the latest protocol ALL '97. Cranial irradiation had been successfully replaced by a long course of intrathecal methotrexate injections for the majority of patients. Age (1 year10 years) sex (male) and white count50 x 10(9)/l plus slow initial bone marrow clearance were consistently the most important independent prognostic indicators during this time period. Rome/NCI criteria accurately predict standard and high-risk groups for B cell lineage, but not consistently for T cell disease. This international collaborative venture might help us to define those truly at highest risk, and how we can optimise therapy for specific subgroups including T-ALL and those with unfavourable cytogenetics.

In the last 20 years, the survival rate for children with acute lymphoblastic leukaemia (ALL) has markedly improved, largely owing to a decrease in relapses. However, children still die from complications of treatment and these are potentially preventable. We have analysed data from three large consecutive national protocols for ALL from 1980 to 1997 [Medical Research Council United Kingdom ALL (MRC UKALL) trials VIII, X and XI] to compare the incidence and causes of treatment-related deaths (TRD). The percentage of TRD has fallen from 9% to 2% (UKALL VIII to XI), largely as a result of a decrease in fatal infections. Deaths during induction have fallen from 3% to 1%, the main causes of death being bacterial, followed by fungal infection, while other causes, chiefly haemorrhage, have not declined. Remission deaths also decreased from 6% to 1%, particularly those deaths due to measles and pneumocystis carinii. More guidelines for surveillance and treatment of infections have been included within progressively more intensive protocols. Risk factor analysis showed increased TRD in patients with Down's syndrome, high leucocyte count and older age in UKALL XI. In contrast, the introduction of blocks of intensification was not associated with an increased death rate. While improved supportive care has reduced the incidence of TRD, there is still scope for further reduction by prompt treatment of suspected infection. Maintenance of herd immunity remains of vital importance in avoiding deaths from measles.

1. The aim of this study was to investigate 6-mercaptopurine (6MP) metabolism by human liver cytosol in vitro. 2. Cytosol was prepared from seven human livers (A-G). A single cytosol (C) was used to optimize incubation conditions. 3. Cytosols A-G were incubated with 6MP at 2, 10 and 500 microM for two fixed times (5 and 48 h). Parent drug, thiopurine and thionucleotide metabolites were quantitated by high performance liquid chromatography at all time points. 4. At 5 and 48 h the 2 microM and 10 microM 6MP incubations contained both 6MP and its initial nucleotide metabolite, thioinosine 5'-monophosphate (TIMP). In addition, the 10 microM 6MP 48 h incubates contained small amounts of 6-thioguanine (6TG, median 0.12 microM). At 500 microM 6MP all seven liver incubates produced a range of metabolites. At 48 h these included thiouric acid, 8-hydroxy-6-mercaptopurine and 6-methylmercaptopurine (median 31, 19.5 and 8.8 microM respectively), with TIMP, 6TG, thioxanthine and thioxanthine nucleotide at median concentrations of 61, 0.79, 2.11 and 0.80 microM respectively. Thioguanine nucleotides, major metabolites measured in vivo, were not detected. 5. These results indicate that the human liver 6MP metabolic profile is dependent upon drug concentration.

Summary. The effect of randomly allocated testicular irradiation on the subsequent incidence of testicular infiltration and disease-free survival was assessed in two Medical Research Council Childhood Leukaemia Trials, UKALL VI and UKALL VII. None of the 83 boys who actually received testicular radiotherapy subsequently developed gonadal disease, whereas 18 of the 163 who were not irradiated did. Despite this there is no apparent difference in disease-free survival for those randomized to receive testicular irradiation compared to those who were not. after a minimum of 8 years follow up. Although prophylactic testicular irradiation appears to prevent subsequent gonadal relapse there is no evidence that it improves overall prognosis when adequate systemic chemotherapy is used. As it has considerable long-term side effects it cannot be recommended as routine therapy.

As a prelude to a nationwide randomized trial of thioguanine (TG) versus mercaptopurine (MP) for childhood lymphoblastic leukaemia we compared a pilot group of 23 children taking TG with a matched group taking MP. We assessed drug tolerance based on haematological toxicity and measured erythrocyte (RBC) concentrations of thioguanine nucleotides (TGN). The median tolerated dose of TG was 30 mg/m2 compared to 55 mg/m2 for MP. There was no difference in the pattern of anaemia or neutropenia between the two groups, but dose-limiting thrombocytopenia was more evident in the TG children (P0.001), four of whom had a decrease in platelet count to20 x 10(9)/l compared to only one on MP. The median RBC TGN concentration for those on 40 mg/m2 TG was 1726 pmol/8 x 10(8) RBCs compared with 308 pmol/8 x 10(8) RBCs for those on 75 mg/m2 MP (P0.0001). There was an inverse correlation between RBC TGNs and neutrophil count in the MP group but not in those on TG. No correlation between metabolite concentration and thrombocytopenia was found in either group. These results provide further evidence that TG has a selective effect on platelets. They also showed that RBC TGN were, on average, 5-fold higher in those taking TG but did not obviously relate to myelotoxicity as found in children on MP. The higher concentrations seen may partly reflect the erythrocyte's ability to metabolize TG directly to TGN by pathways not open to MP.

Paediatric Oncology. Clinical Practice and Controversies. 2nd Ed. Edited by C R Pinkerton and P N Plowman. (Pp 799; £135 hardback.) Chapman and Hall Medical, 1997. ISBN 0-412-63080-X. American textbooks contain few citations to articles published outside the United States, a form of literary chauvinism that sometimes denies the reader a balanced view of the world, so it is pleasing to see that by recruiting authors almost exclusively from Europe, Ross Pinkerton and Nick Plowman have produced an alternative to the big American texts rather than a competitor. Like any multiauthor effort it has its good and its not so good sections, but …

This paper describes a specific and sensitive reversed-phase HPLC assay for the measurement of 6-methylthioguanine (methyl-TG) and methyl-TG nucleotides (methyl-TGNs) in red blood cells (RBCs), which is suitable for routine clinical use. Briefly, an ethyl acetate extract of RBCs is evaporated and reconstituted in 0.1 M HCl. The methyl-TG is separated from other thiopurines by reversed-phase HPLC and quantitated using UV detection. For the measurement of methyl-TGNs the free base (methyl-TG) is obtained by acid hydrolysis of the nucleotide back to the parent thiopurine. The intra-assay C.V. over the concentration range of 0.055-1.10 nmol methyl-TG per 4x10(8) (100 microl) RBCs ranged from 2.8 to 8.5%, and the mean recovery of methyl-TG over the calibration range was 61.6% (coefficient of variation, C.V., 3.8%). The lower limit of reproducibility was 0.055 nmol extracted from 100 microl RBCs. Analysis of blood samples from children with leukaemia receiving 6TG chemotherapy, revealed RBC methyl-TGNs at concentrations ranging from 323 to 1365 pmol per 8x10(8) RBCs. No methyl-TG was detected in any of the patient samples.

The relationship between the prescribed dose of drugs during continuing (maintenance) therapy, the degree of marrow suppression caused, and subsequent event-free survival was examined in a cohort of 740 children with lymphoblastic leukaemia treated on MRC UKALL X. Girls, younger children, and patients who had received intensification treatment, were prescribed lower doses of mercaptopurine, became neutropenic more readily, and had more interruptions of treatment. Children who had one or more episodes of neutropenia with a count of0.5 x 10(9)/l had a better prognosis than those who never became neutropenic. We conclude that early intensification treatment influences the probability of neutropenia during continuing treatment and that patients exhibiting myelosuppression during this phase of treatment have a better chance of prolonged remission.

Daily 6-mercaptopurine (6MP) forms the backbone of continuing chemotherapy for childhood lymphoblastic leukaemia (ALL). A major metabolic route is catalysed by thiopurine methyltransferase (TPMT). TPMT deficiency occurs in 1 in 300 individuals and results in high concentrations of thioguanine nucleotides (TGNs), cytotoxic 6MP metabolites. A leukaemic child taking 6MP repeatedly developed profound pancytopenias. TPMT deficiency was confirmed. TGN formation was then studied on attenuated 6MP dosages. Four weekly oral doses of 75 mg/m2 6MP produced TGNs of 2348 pmol/8 x 10(8) red cells, nearly double the maximum TGNs recorded in ALL children with TPMT activity taking long term daily 75 mg/m2 6MP. Grossly elevated TGN concentrations were also produced at 10% standard 6MP dosage (7.5 mg/m2 daily), accompanied by unacceptable 6MP toxicity (neutropenia, diarrhoea, vomiting). The child was eventually stabilised on 10% alternate day therapy and after 15 weeks TGNs were 1670 pmol, just above the upper end of the TGN range for ALL children with TPMT activity.

At the commencement of UKALL XI, a national MRC trial for childhood lymphoblastic leukaemia (ALL), the therapy included a bolus of daunorubicin (DR) on the first 2 d of the protocol. This component of treatment was subsequently withdrawn because of concern about long-term cardiotoxicity. All children both before and after this change of policy had their marrow status at the end of the first week assessed by central review as part of the trial to examine the clinical importance of the rate of disease clearance. This also afforded an opportunity to observe the effect of DR on gross residual disease at an early stage of therapy. 1419 children were studied: 342 received DR ('recipients'), 1077 did not. 44% of the recipients completely cleared their marrow of blast cells after 8 d compared with 13% of the non-recipients (chi2 = 158.2, P0.0001). The difference in the proportion with massive residual disease (80% blasts) was less impressive but there was still a difference in favour of DR recipients (DR 9%, no DR 15%; chi2 = 7.7, P = 0.006). The rate of disease clearance correlated with disease-free survival for both recipients and non-recipients, but there was no significant difference in outcome when comparing the two groups with each other, either in terms of disease-free or relapse-free survival. DR accelerated the rate of blast cell disappearance from the marrow but the difference this made to disease free survival is small or non-existent. It appears to be the relative speed of response to a given therapeutic regimen that is prognostically important rather than the absolute rate of response when comparing one treatment with another.

In childhood acute lymphoblastic leukaemia, complete remission is usually followed by relapse unless patients receive prolonged outpatient “maintenance” treatment based on daily oral 6-mercaptopurine and weekly methotrexate.1 When patients relapse unexpectedly some months or years after completing their planned schedule of treatment (as still occurs in 20–30% of patients in Britain), the maintenance component of treatment has probably failed for some reason. One contributory factor used to be insufficient doses of antimetabolites. Before 1980, four year disease free survival in Britain was less than 50%. Then a more rigid and detailed national protocol was introduced, where maintenance was more aggressively applied and attenuation of the drug dose was not left up to the individual physician. The result was an increase in toxicity accompanied by a 15–20% improvement in long term survival.2 This experience has persuaded paediatric oncologists in Britain to prescribe the maximum tolerated dose of antimetabolites and to avoid interruptions to treatment wherever possible. So far, so good. But the story does not end there. It is now becoming increasingly apparent that some children simply do not take the drugs they are prescribed. Based on experience with asthma,3 tuberculosis,4 cystic fibrosis,5 diabetes,6 and penicillin prophylaxis for sickle cell disease,7 we know that children often fail to follow important diets or treatment schedules. It …

To determine whether skin puncture blood can be used reliably for CD4 lymphocyte counts, the numbers of the major subsets of lymphocytes were assessed in paired venous and skin puncture blood samples from 22 children and 10 adults. Paired values were highly correlated, with skin puncture values being about 7% higher than venous values for each cell type. Differences were of borderline statistical significance for total lymphocytes and for each subset except CD3+ CD8+ T lymphocytes. Nevertheless, the magnitude of the differences was small and unlikely to be of clinical importance, and it seems that skin puncture samples may be preferable for CD4 counts in children or adults with difficult venous access.

AIMS--Children in a United Kingdom national trial for relapsed non-B lymphoblastic leukaemia (ALL) had their diagnostic and relapse marrow cytomorphology compared to see what changes occur during the evolution of the disease. METHODS--Each relapse slide was assessed blindly for French American British (FAB) type and other morphological features by a panel of three independent microscopists without reference to each other or any diagnostic material. Diagnostic slides had been assessed by the same panel on an earlier occasion. RESULTS--A total of 134 consecutive children was studied. Six (5%) were classified as FAB type L2 at diagnosis, compared with 18 (13%) at relapse (a difference of 9%). Twenty two (16%) changed their FAB type, 17 (13%) from L1 to L2 and five (4%) from L2 to L1. The FAB score fell at relapse in 34 children and rose in 14, a difference of 14%. Cell size was the commonest feature to change (increasing in 22 and diminishing in nine) followed by prominent nucleoli (appearing in 21 and disappearing in six). Forty four (33%) children had vacuolated blasts at diagnosis, compared with 48 (36%) at relapse. Twenty five changed their vacuole score substantially, 14 gaining > 10% and 11 falling < 10%. CONCLUSIONS--These findings reflect the variability of lymphoblast cytomorphology, but also show a trend for cells to have more prominent nucleoli and greater size at relapse. Factors controlling these features of the FAB type are unknown, but they may simply be related to the growth fraction of a particular disease and not to any lineage specific biological feature.

As part of a programme assessing the pharmacokinetics of oral thiopurines given for lymphoblastic leukaemia, we assayed intracellular metabolites of mercaptopurine in children from all over the United Kingdom who were given a standard dose of the drug. The metabolites we measured, thioguanine nucleotides and methylmercaptopurines, are products of two competing metabolic pathways and would be expected to show an inverse correlation. A total of 327 children from 17 centres in the UK were studied. All were on the same therapeutic schedule of mercaptopurine. All had been on an unattenuated full protocol-directed dose (at least 75 mg m-2) for a minimum of 7 days before assay. There was a very wide variation in the concentration of the two metabolites measured; the thioguanine nucleotides ranged from 0 to 1255 pmol per 8 x 10(8) red cells (median 289, lower quartile 210, upper quartile 377) and the methylmercaptopurine metabolites ranged from 0 to 46.3 nmol per 8 x 10(8) red cells (median 5.18, lower quartile 2.31, upper quartile 11.59). The anticipated negative correlation was not apparent, but the ratio between the two was not randomly distributed. No child had both metabolite concentrations in the upper quartiles, but in 32 (10%) children the concentration of both metabolites was in the lower quartile. Of the 32, only one metabolite was detected in four and none at all in six. The most likely explanation for these findings is that a minority of children with lymphoblastic leukaemia fail to take oral mercaptopurine either totally or intermittently. The extent of the problem is unknown, but we suspect it may be clinically important in at least 10% of patients.

The clinical usefulness of the measurement of red cell zinc protoporphyrin (ZPP), an indicator of iron-deficient erythropoiesis, was assessed in a group of UK children undergoing investigation for red cell microcytosis. Of 213 children studied, 136 had increased ZPP values. Of these, 86 also had reduced iron stores as indicated by serum ferritin concentration. The 50 children with increased ZPP and normal ferritin values could be divided into two main groups. One group comprised 28 children who had evidence of coexistent infection or inflammatory disease. The other included 21 children who had beta-thalassemia trait (n = 19) or disease (n = 2). Among the 77 children with normal ZPP values, 22 had reduced serum ferritin concentrations and 45 did not, nor did they have evidence of beta-thalassemia. Microcytosis in some of these children could have been due to alpha-thalassemia trait. Measurement of ZPP is a simple, quick, and relatively cheap method of confirming the presence of iron-deficient erythropoiesis even when inflammation makes serum ferritin measurements unreliable. It is not as sensitive as the ferritin assay to the early stages of iron deficiency, and its specificity is reduced by the occurrence of raised values in most children with beta-thalassemia trait. Where there is microcytosis, normal values, together with normal hemoglobin A2 and serum ferritin concentrations, are likely to indicate alpha-thalassemia trait.

The important causes of anaemia in childhood differ from those in adults. Anaemia is a physical sign that needs explanation and this article aims to bring out important points in the history, examination and laboratory tests. Key features of a number of anaemias presenting in childhood are outlined.

We have examined the factors influencing prognosis in over 4000 children with acute lymphoblastic leukaemia (ALL) aged 1-14 who have been treated on consecutive MRC UKALL trials from 1972 to 1990. During this time the results of treatment have improved steadily but are consistently superior in girls when compared with boys; the 5-year event-free survival in girls improving from 51% to 71% and in boys from 31% to 57%. These results were independent of age and presenting leucocyte count. Boys not only had a testicular relapse rate of 10% but an excess of bone marrow relapse, particularly evident after 2 years from diagnosis. Other prognostic factors included organomegaly and the morphology of leukaemic blast cells; immunophenotype of the leukaemia, however, had no independent significance after allowance for age, sex and leucocyte count. The influence of sex on prognosis was reaffirmed when we examined various methods of identifying children at highest risk of treatment failure for whom alternative therapy such as bone marrow transplantation might be justified. In MRC UKALL X children had been deemed 'high risk' on the basis of leucocyte count alone, but with further follow-up it has become apparent that girls with an initial leucocyte count of > 100 x 10(9)/l have a similar prognosis to boys with a lower count. We therefore derived a risk score based on sex, age and count which has given better discrimination between standard risk (66% 5-year survival) and poor risk (39%) survival than other methods. This group of worse-risk children includes 16% of boys but only 3% of all girls. Gender remains an important prognostic factor in UKALL trials and there are very few girls who are at highest risk of treatment failure. The reasons for this remain unclear, but the pattern of relapses suggests that boys more often get inadequate systemic therapy. We postulate that the reasons for treatment failure may relate to sensitivity to continuing (maintenance) chemotherapy.

Acute lymphoblastic leukaemia (ALL) is rare under 1 year and has a poor prognosis. Only 14 of 48 infants treated on two consecutive MRC UKALL trials remain alive in first remission. Forty infants have subsequently been treated on a protocol incorporating further intensification with an option for high-dose chemotherapy and autologous or allogeneic bone marrow transplantation. The results show no improvement over previous trials largely due to the number of remission deaths; four of nine being associated with toxicity of 5 days of etoposide and cytarabine. Only three of 11 children treated by high-dose chemotherapy and transplantation remain alive in remission. Multivariate analysis of the factors influencing prognosis in all 88 infants showed that only age was significant. Event-free survival was 40% at 5 years for children over 26 weeks but under 10% for younger children. These results show the susceptibility of infants to the toxicity of intensive chemotherapy and do not support the use of short term high-dose chemotherapy alone in the management of infant leukaemia. Despite the unique biological features of infant ALL it appears that these patients also may benefit from longer courses of treatment with a maintenance (continuing) phase.

Blast cell chromosome abnormalities at presentation in childhood acute lymphoblastic leukemia (ALL) are common, and different patterns are known to be related to outcome. In contrast, the frequency and importance of further changes at the time of relapse remain unclear. Blast cell karyotype evolution was therefore studied in a group of children with recurrent disease. Of 134 consecutive children diagnosed between 1982 and 1992, 31 had a marrow relapse, and 24 had complete cytogenetic studies at both diagnosis and the time of recurrence. Fourteen (58%) of the 24 showed additional chromosomal abnormalities at relapse, 5 (21%) retained abnormalities identical to those seen at diagnosis, and 5 (21%) remained cytogenetically normal. The 14 with additional changes had shorter first remissions and showed shorter survival after relapse compared with the others. These findings indicate that emergency of cytogenetically recognizable subclones during the progression of childhood ALL could be a marker of more resistant disease.

Summary Immune tolerance was induced in five consecutive young boys with haemophilia and factor VIII inhibitors using frequent conventional doses of human factor VIII. All therapy was given at home by parents and the four youngest boys had surgically implanted central venous catheters (Port-a-Cath). Two catheters eventually became infected after 2 and 4 years respectively, otherwise the devices were trouble-free and liked by the families concerned. Regular domiciliary factor VIII therapy in pre-school children is not difficult with an aid to venous access and immune tolerance can be achieved in those developing factor VIII inhibitors.