The prognostic significance of morphological features in childhood acute lymphoblastic leukaemia

Prognostic significance of the revised French-American-British classification for acute lymphocytic leukaemia

The French-American-British (FAB) classification of acute lymphocytic leukaemia (ALL) has recently been modified to improve its reproducibility. We therefore thought it beneficial to test the utility of this modified classification in the prognosis of children with ALL. Eighty-eight patients of less than 18 years of age with ALL were subtyped according to the modified FAB classification by two independent observers. The initial concordance was 86%. Seventy per cent of the patients were subtyped as L1, 27% as L2 and 3% as L3. Patients with L3 subtype were not analysed further. No significant differences were observed between L1 and L2 subtypes when the distribution of other prognostic factors were examined. No differences were observed between L1 and L2 subtypes in the achievement of complete remission. Patients with L1 morphology demonstrated no significant increased duration of first remission or survival when compared to patients with L2 morphology. We conclude that the morphology of lymphoblasts may not be an independent prognostic variable in patients with ALL.

Periodic acid Schiff reaction in childhood lymphoblastic leukaemia. The Medical Research Council Working Party on Childhood Leukaemia

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.

'MACHO' chemotherapy for stage IV B cell lymphoma and B cell acute lymphoblastic leukaemia of childhood. United Kingdom Children's Cancer Study Group (UKCCSG)

An intensive 6-month schedule of drugs was devised with both systemic and central nervous system activity, known by the acronym 'MACHO', to treat 24 newly and consecutively diagnosed children, 13 with stage IV B-cell non-Hodgkin's lymphoma (B-NHL) and 11 with B-cell acute lymphoblastic leukaemia (B-ALL). There were three deaths from complications of chemotherapy (two infective, one biochemical). Five children with central nervous system disease at diagnosis (CNS+) received planned additional megatherapy/bone marrow transplants. Event-free survival (EFS) at 1 year for the 11 cases of B-ALL is 64% (95% confidence intervals [CI] 31-89%) and of 13 stage IV B-NHL cases is 50% (95% CI 19-75%). Patients with bulky abdominal disease had a 32% EFS at 1 year (CI 13-68%) compared with 76% (CI 39-94%) for those without bulky abdominal disease. Overall EFS for eight CNS+ patients is 73% at 1 year (95% CI 34-97%) compared with 48% (95% 24-74%) for those without CNS disease (CNS-). However, only two of the CNS+ cases had bulky abdominal disease (patients 10 and 12) and the difference is not significant (P less than 0.5). A score of 1 was given for each of the following potential prognostic features: bulky abdominal disease, pleural effusion and severe renal dysfunction within 48 h of presentation. Patients who scored 0 or 1 fared significantly better than those who scored 2 or 3 (EFS at 1 year 78% [CI 49-95%] versus 24% [6-65%], P less than 0.04). Two patients with a score of 2 survived past 6 months and another is currently well, but has not regenerated his marrow following autologous transplantation. This protocol is relatively effective for patients who have B-ALL, but those patients who have bulky abdominal disease, often associated with severe renal dysfunction, and those with CNS disease, do not fare so well and require new approaches to therapy.

Long survival in childhood lymphoblastic leukaemia

Long term follow-up of 378 children with acute lymphoblastic leukaemia (ALL) treated at a single centre showed that at six years from diagnosis 202 (53%) were alive, of whom 140 (37%) remained in first remission. Only three children had a first relapse after six years. Children who survived six years despite a single extramedullary relapse in the testis or CNS were likely to remain in second remission but patients with previous marrow or with multiple relapses continued at risk for up to ten years from diagnosis. Presenting factors influencing event-free survival were: leucocyte count, age and sex. After allowing for these factors morphological (FAB) subtype and liver enlargement retained their prognostic significance. Immunological type of ALL was not of independent prognostic significance, except for the small number of patients with B-ALL. Most factors lost their significance after 2-4 years. It is concluded that patients alive 6 years from diagnosis without relapse or even with a single extramedullary relapse of ALL, have a high chance of prolonged survival and cure.

The clinical significance of blast cell morphology in childhood lymphoblastic leukaemia

The morphological classification of ALL based on the FAB co-operative group's criteria is capable of identifying 10-15% of children with L2 disease who, given similar treatment, will fare less well than the 85-90% with the L1 variant. The significant features defining L2 morphology are a low cellular nuclear: cytoplasmic ratio and the presence of nucleoli. Children with L2 disease do not have higher leucocyte counts but are older, have "common" ALL less frequently, and more often have well-preserved marrow function at diagnosis. Their poor outlook is manifest not only by their higher relapse rate but also by a higher proportion failing to remit in the first instance. L2 morphology does not necessarily "breed true" and can arise in a small proportion of patients with previous L1 disease at the time of relapse. Other striking morphological features of lymphoblasts, including azurophil granules, vacuoles and "hand mirror" cells, have yet to have their significance defined, though the latter feature may be an unfavourable finding.

Comparison of morphology in ALL at presentation and relapse

A high frequency of conversion from L1 to L2 morphology in ALL at relapse has been reported in studies made without benefit of the French-American-British (FAB) scoring system. We compared the lymphoblast morphology at presentation and first hematologic relapse for 50 consecutive children with acute lymphoblastic leukemia using the FAB scoring system to determine the frequency of morphologic conversion. Forty-eight patients presented with L1 morphology, 42 of whom (88%) relapsed with L1 blasts, four (8%) with L2 blasts, and two (4%) with blasts intermediate between L1 and L2. Two presented with L2 morphology, both relapsing with L2 blasts. These data do not support previous findings of a high frequency of conversion from L1 to L2 at relapse. They suggest, instead, that L2 morphology is not a common morphologic expression of initial treatment failure.

A study of the reproducibility of the diagnostic criteria for acute leukaemia

The Leukaemia Group of Middle Sweden recently started a new multicentre study of treatment of adult patients with acute leukaemia from 6 centres. The criteria for the diagnosis, subclassification, degree of leukaemic bone marrow infiltration, remission and relapse are to be used by the morphologists of 6 different pathology departments. The reproducibility of the criteria has been studied by 3 of the morphologists concerned, in a retrospective review of a strictly consecutive series of 79 adult patients treated at Södersjukhuset, Stockholm, Sweden, in the years 1978 to 1981. The results show that the reproducibility of the criteria and the concordance of the morphologists when using them increased when the criteria were made more detailed and precise.

Haemoglobin and prognosis in childhood acute lymphoblastic leukaemia

Two hundred and nine children presenting consecutively with acute lymphoblastic leukaemia to a regional paediatric oncology unit were investigated to determine the prognostic significance of various factors at diagnosis. There was a strong positive correlation between the pretreatment haemoglobin level and the percentage of bone marrow blast cells in S phase of the cell cycle as assessed by flow cytometry. Patients with T- and B-cell leukaemia had significantly higher haemoglobin levels than non-B non-T patients. In patients with total white cell counts less than 20 X 10(9)/l, aged less than 13 years, and no mediastinal mass, there was no association of haemoglobin with length of first remission. However, among those with white blood counts greater than 20 +/- 10(9)/l there was a strong positive trend towards shorter remission with higher haemoglobin levels. Children with high white blood counts at diagnosis and low haemoglobin levels may have a better prognosis than predicted by the white blood count alone.

The morphological classification of acute lymphoblastic leukaemia: concordance among observers and clinical correlations

The degree of concordance in the morphological classification of ALL was assessed by the FAB group after two successive reviews of 200 and 100 slides respectively. As a result, a simple scoring system for types L1 and L2 is proposed based on the following four features: (1) nuclear cytoplasmic ratio, (2) presence, prominence and frequency of nucleoli, (3) regularity of nuclear membrane outline, and (4) cell size. By this method, the overall concordance by seven observers (agreement of 7:0 or 6:1 only) increased from 63% to 84%. A significant difference in the incidence of the ALL morphological types in children (less than or equal to 15 years) and adults (greater than 15 years) was found: 74% of L1 cases were children while 66% of L2 cases were adults (P less than 0.001). No significant differences were observed in the incidence of L3 in children and adults or between L1 and L2 according to the membrane phenotype of the blast cells. All L3 cases had B-cell characteristics. A better prognosis for L1 and a higher relapse rate for L2 has been found in several recent reports; The present study may facilitate the morphological analysis of ongoing clinical trials in ALL by improving the reproducibility of the FAB classification.

Morphological metamorphosis in relapsing lymphoblastic leukemia

Blast cell morphology was assessed at diagnosis and subsequent bone marrow relapse in 33 unselected patients with lymphoblastic leukemia (ALL). Each marrow was classified 'blind' according to the French-American-British (FAB) criteria, and it was found that 19 of 24 (79%) patients initially typed as FAB L1 changed to FAB L2 during the course of their disease, but no patient made the reverse morphological change (p is less than 0.001). Five patients retained FAB L1 appearances; these included three of the four who had T-cell markers. One patient typed as FAB L3 did so consistently. This study indicates that FAB L2 ALL frequently emerges as a treatment-resistant offshoot of FAB L1 and provides further evidence that this marks a more aggressive form of the disease.

A score at diagnosis for predicting length of remission in childhood acute lymphoblastic leukaemia

Thirty-two variables at diagnosis of acute lymphoblastic leukaemia (ALL) were studied in an unselected population-bases series of 209 children. Twelve variables had individually a statistically significant effect on the duration of first remission. A multivariate analysis using data on the 199 children who went into complete remission showed that all significant variation in remission times could be explained by only 3 variables acting simultaneously. These were the total white blood count (WBC) at diagnosis, the Franco-American-British (FAB) classification of blast morphology and the percentage of lymphoblasts with PAS+ coarse granules or blocks. A simple scoring system (for WBC add 1 if less than 20 X 10(9)/1, add 2 if 20 - 50 X 10(9)/1, add 3 if greater than or equal to 50 X 10(9)/1; for L2 or L3 leukaemia add 1; for PAS+ less than 5% add 1) separated patients into risk groups with widely different median lengths of first remission. Application of the risk score improves the prediction of the outcome of treatment, and the clinical trials, allows more accurate stratification, less extensive data collection and simpler analysis.

Relationship between the pretreatment proliferative activity of marrow blast cells and prognosis of acute lymphoblastic leukaemia of childhood

Pretreatment marrow blast cells were studied in 38 boys and 27 girls (aged 1-14) with acute lymphoblastic leukaemia by flow cytometry after staining with propidium iodide.The percentage of blast cells in the S phase of the cell cycle ranged from 1% to 40% (median 6%). A correlation was found between the percentage of cells in S and the morphological classification of the French American British Cooperative Group (FAB), presence of T or B cell markers, haemoglobin concentration, blast size, bone pain, platelet count, and an inverse correlation with coarse granule and block staining with Periodic-acid-Schiff (PAS).63 of the 65 children attained complete remission. During the first 24 months of follow up there were fewer relapses (P = 0·054), and deaths (P = 0·004) in those children with 6% or fewer blasts in S phase. The difference was most marked in the first 12 months with 4 relapses out of 33 in the group with 6% or fewer cells in S compared with 13/30 in the group with > 6% cells in S.In order to investigate the prognostic significance of the pretreatment proliferative studies in greater detail, remission duration was correlated with 17 presenting features. Each feature was correlated individually and then the simultaneous effect of all the features was assessed by stepwise multiple regression.Only 3 features of the disease at diagnosis were individually correlated with duration of remission. These were% cells in S (P < 0·001), log white cell blood count (WBC) (P < 0·01) and the presence of T- or B-cell surface markers (P < 0·05). However, the multiple regression analysis showed that cell markers were not an independent prognostic feature, whereas the percentage cells in S and log WBC were independently and significantly correlated with duration of first remission (P < 0·001 in each case).