Leukaemia in Childhood and Young Adult Life

Trends in childhood leukemia incidence in urban countries and their relation to environmental factors, including space weather

Leukemia is the most common cancer in children. Its incidence has been increasing worldwide since 1910th, suggesting the presence of common sources of the disease, most likely related to people's lifestyle and environment. Understanding the relationship between childhood leukemia and environmental conditions is critical to preventing the disease. This discussion article examines established potentially-carcinogenic environmental factors, such as vehicle emissions and fires, alongside space weather-related parameters like cosmic rays and the geomagnetic field. To discern the primary contributor, we analyze trends and annual variations in leukemia incidence among 0-14-year-olds in the United States, Canada, Australia, and Russia from 1990 to 2018. Comparisons are drawn with the number of vehicles (representing gasoline emissions) and fire-affected land areas (indicative of fire-related pollutants), with novel data for Russia introduced for the first time. While childhood leukemia incidence is rising in all countries under study, the rate of increase in Russia is twice that of other nations, possibly due to a delayed surge in the country's vehicle fleet compared to others. This trend in Russia may offer insights into past leukemia levels in the USA, Canada, and Australia. Our findings highlight vehicular emissions as the most substantial environmental hazard for children among the factors examined. We also advocate for the consideration of potential modulation of carcinogenic effects arising from variations in cosmic ray intensity, as well as the protective role of the geomagnetic field. To support the idea, we provide examples of potential space weather effects at both local and global scales. The additional analysis includes statistical data from 49 countries and underscores the significance of the magnetic field dip in the South Atlantic Anomaly in contributing to a peak in childhood leukemia incidence in Peru, Ecuador and Chile. We emphasize the importance of collectively assessing all potentially carcinogenic factors for the successful future predictions of childhood leukemia risk in each country.

Cancer of childhood in sub-Saharan Africa

Measurement of incidence rates of childhood cancer in Africa is difficult. The study 'Cancer of Childhood in sub Saharan Africa' brings together results from 16 population-based registries which, as members of the African Cancer Registry Network (AFCRN), have been evaluated as achieving adequate coverage of their target population. The cancers are classified according to the third revision of the International Classification of Childhood Cancer (ICCC-3) and recorded rates in Africa are compared with those in childhood populations in the UK, France, and the USA. It is clear that, in many centres, lack of adequate diagnostic and treatment facilities leads to under-diagnosis (and enumeration) of leukaemias and brain cancers. However, for several childhood cancers, incidence rates in Africa are higher than those in high-income countries. This applies to infection-related cancers such as Kaposi sarcoma, Burkitt lymphoma, Hodgkin lymphoma and hepatocellular carcinoma, and also to two common embryonal cancers - retinoblastoma and nephroblastoma. These (and other) observations are unlikely to be artefact, and are of considerable interest when considering possible aetiological factors, including ethnic differences in risk (and hence genetic/familial antecedents). The data reported are the most extensive so far available on the incidence of cancer in sub Saharan Africa, and clearly indicate the need for more resources to be devoted to cancer registration, especially in the childhood age range, as part of an overall programme to improve the availability of diagnosis and treatment of this group of cancers, many of which have-potentially-an excellent prognosis.

Editorial: Childhood Cancer in sub-Saharan Africa

Measurement of incidence rates of childhood cancer in Africa is difficult. The study 'Cancer of Childhood in sub Saharan Africa' [Stefan C, Bray F, Ferlay J, Parkin DM and Liu B (2017) Cancer of Childhood in sub-Saharan Africaecancer11(755)] brings together results from 16 population-based registries which, as members of the African Cancer Registry Network (AFCRN), have been evaluated as achieving adequate coverage of their target population. The cancers are classified according to the third revision of the International Classification of Childhood Cancer (ICCC-3) and recorded rates in Africa are compared with those in childhood populations in the UK, France, and the USA. It is clear that, in many centres, lack of adequate diagnostic and treatment facilities, leads to under-diagnosis (and enumeration) of leukaemias and brain cancers. However, for several childhood cancers, incidence rates in Africa are higher than those in high income countries. This applies to infection-related cancers such as Kaposi sarcoma, Burkitt lymphoma, Hodgkin lymphoma and hepatocellular carcinoma, and also to two common embryonal cancers-retinoblastoma and nephroblastoma. These (and other) observations are unlikely to be artefact, and are of considerable interest when considering possible aetiological factors, including ethnic differences in risk (and hence genetic/familial antecedents). The data reported are the most extensive so far available on the incidence of cancer in sub Saharan Africa, and clearly indicate the need for more resources to be devoted to cancer registration, especially in the childhood age range, as part of an overall programme to improve the availability of diagnosis and treatment of this group of cancers, many of which have-potentially-an excellent prognosis.

Incidence and Survival of Childhood Cancer in Korea

Purpose

An epidemiologic study of childhood cancer would provide useful information on cancer etiology and development of management guidelines.

Materials and Methods

Data from the Korea National Cancer Incidence Database were used to examine the incidence and survival of cancer in patients aged 0-14 years. Patients were grouped according to the International Classification of Childhood Cancer, 3rd edition. Age-specific and age-standardized incidences per million and estimated annual percentage change (APC) were calculated by sex and age. Five-year relative survival was calculated for four periods from 1993 to 2011.

Results

The study comprised 15,113 patients with malignant neoplasms. Age-standardized incidence rates for all cancers were 134.9 per million children in 1999-2011 and 144.0 and 124.9 per million for males and females, respectively (M/F ratio, 1.2; p < 0.05). The highest incidences were observed for ‘leukemias, myeloproliferative diseases, and myelodysplastic diseases’ (group I) (46.4), ‘central nervous system neoplasms’ (group III) (18.3), and ‘lymphomas and reticuloendothelial neoplasms’ (group II) (13.4). Age-standardized incidence increased from 117.9 in 1999 to 155.3 in 2011, with an APC of 2.4% (95% confidence interval, 2.1 to 2.7). There was a significant increase of APC in ‘neuroblastoma and other peripheral nervous cell tumors’ (group IV) (5.6%) and ‘other malignant epithelial neoplasms and malignant melanomas’ (group XI) (5.6%). The 5-year relative survival rate for all childhood cancers improved significantly from 56.2% (1993-1995) to 78.2% (2007-2011) (males, 56.7% to 77.7%; females, 55.5% to 78.8%).

Conclusion

This study provides reliable information on incidence and survival trends for childhood cancer in Korea.

The biography of the immune system and the control of cancer: from St Peregrine to contemporary vaccination strategies

BACKGROUND

The historical basis and contemporary evidence for the use of immune strategies for prevention of malignancies are reviewed. Emphasis is focussed on the Febrile Infections and Melanoma (FEBIM) study on melanoma and on malignancies that seem to be related to an overexpression of human endogenous retrovirus K (HERV-K).

DISCUSSION

It is claimed that, as a result of recent observational studies, measures for prevention of some malignancies such as melanoma and certain forms of leukaemia are already at hand: vaccination with Bacille Calmette-Guérin (BCG) of new-borns and vaccination with the yellow fever 17D (YFV) vaccine of adults. While the evidence of their benefit for prevention of malignancies requires substantiation, the observations that vaccinations with BCG and/or vaccinia early in life improved the outcome of patients after surgical therapy of melanoma are of practical relevance as the survival advantage conferred by prior vaccination is greater than any contemporary adjuvant therapy.

SUMMARY

The reviewed findings open a debate as to whether controlled vaccination studies should be conducted in patients and/or regions for whom/where they are needed most urgently. A study proposal is made and discussed. If protection is confirmed, the development of novel recombinant vaccines with wider ranges of protection based, most likely, on BCG, YFV or vaccinia, could be attempted.

Paediatric cancer in low-income and middle-income countries

Patterns of cancer incidence across the world have undergone substantial changes as a result of industrialisation and economic development. However, the economies of most countries remain at an early or intermediate stage of development-these stages are characterised by poverty, too few health-care providers, weak health systems, and poor access to education, modern technology, and health care because of scattered rural populations. Low-income and middle-income countries also have younger populations and therefore a larger proportion of children with cancer than high-income countries. Most of these children die from the disease. Chronic infections, which remain the most common causes of disease-related death in all except high-income countries, can also be major risk factors for childhood cancer in poorer regions. We discuss childhood cancer in relation to global development and propose strategies that could result in improved survival. Education of the public, more and better-trained health professionals, strengthened cancer services, locally relevant research, regional hospital networks, international collaboration, and health insurance are all essential components of an enhanced model of care.

Childhood cancer: incidence and early deaths in Argentina, 2000-2008

INTRODUCTION

Knowledge on the epidemiology of childhood cancer in Latin America is limited. The Argentinean Oncopaediatric Registry (ROHA) has been active since 2000. Data for 2000-2008 are described in the present work.

MATERIALS AND METHODS

ROHA is fed from a network of paediatric units and population-based cancer registries. Cases are coded by the International Classification of Childhood Cancer.

RESULTS

A total of 11447 children aged 0-14 diagnosed with cancer were reported. Histologically verified cases and cases identified only through death certificates were respectively 91% and 6%. The annual age of standardised incidence rate of all cancers was 128.5 per million. Proportions of leukaemia's, lymphoma's and Central Nervous System tumours were 37%, 13% and 18%. The distribution of rates of acute lymphatic leukaemia by the year of age showed a peak around age 3. Eighty percent of the patients are treated in public hospital and around 35% migrate for some of the treatment. Deaths within a month of diagnosis were 5% in 2000 and 3% in 2008.

CONCLUSIONS

Childhood cancer incidence in Argentina is somewhat lower than in North American and in Western European countries: the deficit is mainly due to tumours of the Central Nervous system and other solid tumours. Childhood cancer incidence did not show any tendency to increase. The possible excess of Hodgkin lymphoma in the Northeast region requires additional studies. Early deaths after diagnosis indicate an unsatisfactory state of the overall organisation of childhood cancer care. Data from ROHA are used for decision making at local and national levels.

Epidemiology of childhood cancer

At least in economically developed countries, in the last decades, the incidence of childhood cancer has increased and the increase is unlikely to be an artefact. Causes of the increase have not been identified: a role of preventable environmental exposures is possible. Changes have also occurred in the age distribution of acute lymphoblastic leukaemia.Currently, children with cancer can be successfully treated and cured. However, access to the best therapy differs widely among countries because of the unequal distribution of resources for cancer care. Any double standard in the fate of children with cancer is ethically unacceptable.

Childhood acute lymphoblastic leukemia is triggered by the introduction of immunization against diphtheria

BACKGROUND

Childhood acute lymphoblastic leukemia has prenatal origin. Leukemogenic translocations originating during fetal life are insufficient for overt leukemia. Transgenic TEL-AML1 mice have failed to develop leukemia. Additional postnatal events are required for full leukemogenesis. The significant peak-age (2-5 years) first appeared after 1940 in Great Britain. Since then, childhood leukemia has almost unchangeable incidence. In 1940 the introduction of immunization against diphtheria on a national scale was begun in Great Britain.

HYPOTHESIS

Childhood acute lymphoblastic leukemia is triggered by vaccination against diphtheria.

TESTING THE HYPOTHESIS

Epidemiological survey for leukemia cases among "exemptors" and unvaccinated cases among ALL children should be done. Simultaneously, the transgenic TEL-AML1 mice should be vaccinated with the diphtheritic toxoid.

IMPLICATIONS OF THE HYPOTHESIS

If there is no leukemia among the "exemptors", no unvaccinated among ALL, and some mice develop leukemia upon vaccination childhood leukemia will be prevented by massive neonatal screening for leukemogenic genetics and/or with a new vaccination schedule.

Childhood leukemia, electric and magnetic fields, and temporal trends

During the past 25 years concern has been raised about the possible health effects of extremely low frequency (ELF) electric and magnetic fields (EMFs), particularly regarding childhood leukemia. Comparison of changes in electricity consumption (a surrogate for exposure) to changes in childhood-leukemia rates, known as ecologic correlation, have been used to argue both for and against the association between magnetic fields and childhood leukemia. In this paper we explore what can be learned from such an ecologic approach. We first examine separately the evidence on trends in exposure to EMFs and on trends in leukemia rates, and then compare the two. Both incidence rates and exposures have increased, but there are so many approximations and assumptions involved in connecting the two trends that we cannot regard the ecologic evidence as providing any meaningful evidence for or against a causal link.

Geographical patterns and time trends of cancer incidence and survival among children and adolescents in Europe since the 1970s (the ACCISproject): an epidemiological study

BACKGROUND

Cancer is rare before age 20 years. We aimed to use the European database of childhood and adolescent cancer cases, within the Automated Childhood Cancer Information System project, to estimate patterns and trends of incidence and survival within Europe.

METHODS

Comparable, high-quality data from 63 European population-based cancer registries consisted of 113000 tumours in children and 18243 in adolescents diagnosed in 1970-99. Incidence rates and survival were compared by region (east vs west), period, and malignant disease.

FINDINGS

In the 1990s, age-standardised incidence rates were 140 per million for children (0-14 years) and 157 per million for ages 0-19 years. Over the three decades, overall incidence increased by 1.0% per year (p<0.0001) in children (increases for most tumour types), and by 1.5% (p<0.0001) in adolescents (15-19 years; notable increases were recorded for carcinomas, lymphomas, and germ-cell tumours). Overall 5-year survival for children in the 1990s was 64% in the east and 75% in the west, with differences between regions for virtually all tumour groups; 5-year survival was much the same in adolescents. Survival has improved dramatically since the 1970s in children and adolescents, more so in the west than in the east.

INTERPRETATION

Our results are clear evidence of an increase of cancer incidence in childhood and adolescence during the past decades, and of an acceleration of this trend. Geographical and temporal patterns suggest areas for further study into causes of these neoplasms, as well as providing an indicator of progress of public-health policy in Europe.

Socioeconomic status and risk of childhood leukaemia in Denmark

AIMS

The aim of this study was to assess the influence of socioeconomic status on the risk of childhood leukaemia.

METHODS

A matched case-control design was used. The study population comprised all children (0-14 years old) born and reported to the Danish Cancer Registry between 1976 and 1991 for a diagnosis of leukaemia (n=377). Controls were selected from the Central Population Registry and matched by sex, age, and time of birth. Each child was assigned three categories of socioeconomic status, one corresponding to the annual average income in the municipality of residence at the time of birth, another corresponding to that at the time of diagnosis, and, finally, each family was assigned one of five social classes by use of the job titles of the parents. Conditional logistic regression was used to estimate the effect of socioeconomic status on the risk of childhood leukaemia.

RESULTS

Children born in low-income municipalities had a significantly increased risk of leukaemia (RR=2.71; 95% CI=1.41-5.21; p=0.003), which was higher among those who received their diagnosis before age five (RR=3.43; 95% CI=1.52-7.74; p=0.003). Neither individual social class nor the socioeconomic status of the residential area at the time of diagnosis was convincingly associated with the risk of childhood leukaemia.

CONCLUSIONS

The results suggest that socioeconomic factors associated with community characteristics rather than individual lifestyle are related to the risk of childhood leukaemia and that these factors act early in life.

Epidemiology and genetics of childhood cancer

Childhood cancer is rare everywhere in the world, with age-standardized annual incidence usually between 70 and 160 per million at age 0-14 years. Greater variation is seen between populations for some specific tumour types. Some of the largest variations are geographical and are attributable to environmental factors, whereas variation mainly on ethnic lines seems likely to be a marker of genetic predisposition. A wide range of familial and genetic syndromes is associated with an increased risk of childhood cancer. Virtually all the excess risk of cancer among first-degree relatives of children with cancer can be accounted for by known hereditary syndromes. Studies of weak predisposition and gene-environment interaction have so far shown limited consistency. There are very few established environmental or exogenous risk factors and most of these are infective agents. Many putative risk factors can hardly ever be investigated epidemiologically except by interview or questionnaire studies. Some recent examples illustrate the continuing problems of participation bias and recall bias.

Is the timing of exposure to infection a major determinant of acute lymphoblastic leukaemia in Hong Kong?

The hypothesis that protection of infants from exposure to infectious agents with delayed first exposure to one or more specific agents together contribute to the aetiology of childhood leukaemia, especially common acute lymphoblastic leukaemia (cALL), has substantial indirect support from descriptive epidemiology and case-control studies in developed Western countries. A case-control study of childhood leukaemia diagnosed at ages 2-14 years has now been conducted in Hong Kong. Cases (n=98) formed a consecutive series of Chinese children diagnosed with acute leukaemia; controls (n=228) were identified following a survey using random digit dialling and required to attend for medical examination by a paediatrician. Interviews with mothers were conducted in hospital by one trained interviewer using a structured questionnaire. Odds ratios (OR) and 95% confidence intervals (CI) are reported for exposure variables capable of serving as proxies for exposure to infection in two critical time periods: first year of life, year before reference date (diagnosis for cases, corresponding date for controls). Analyses used logistic regression with adjustment for appropriate confounders. Change of area of residence reduced risk if during the first time period (OR = 0.47 [95% CI 0.23, 0.98]) and increased risk if during the second (OR=3.92, [95% CI 1.47, 10.46]). Reported roseola and/or fever and rash in the first year of life reduced risk (OR=0.33 [95% CI 0.16, 0.68]) whereas tonsillitis in the period 3-12 months before reference date increased risk (OR=2.56 [95% CI 1.22, 5.38]). Some other proxies for exposure to infection at the critical times were associated with predicted patterns of risk but day-care attendance failed to show predicted associations. These results provide support for the delayed exposure hypothesis in an affluent geographical setting in which population exposure to infectious agents is quite distinct from the settings of previous case-control studies.

Historical evidence that residential electrification caused the emergence of the childhood leukemia peak

A peak in childhood leukemia, ages two through four, emerged de novo in the 1920s in the United Kingdom and slightly later in the United States (US). Electrification in US farm and rural areas lagged behind urban areas until 1956. In recent years, childhood leukemia has been associated with residential electromagnetic fields. During 1928-1932, in states with above 75% of residences served by electricity, leukemia mortality increased with age for single years 0-4, while states with electrification levels below 75% showed a decreasing trend with age (P = 0.009). During 1949-1951, all states showed a peak in leukemia mortality at ages 2-4. At ages 0-1, leukemia mortality was not related to electrification levels. At ages 2-4, there was a 24% (95% confidence interval (CI), 8%-41%) increase in leukemia mortality for a 10% increase in percent of homes served by electricity. The childhood leukemia peak of common acute lymphoblastic leukemia may be attributable to electrification.

Age and sex distributions of hematological malignancies in the U.K

This paper reports on an analysis of nearly 27,000 hematological malignancies diagnosed in the U.K. in the 10-year period 1984 to 1993. The unique observations provided in this analysis are the similarity of the sex-specific curves by age for acute myeloid leukemia, myelodysplasia types, polycythemia rubra vera, and myelofibrosis (or myelosclerosis). The unusual age-sex-specific distribution of essential thrombocythemia, suggesting a unique epidemiology, has never been reported before. The unusual female excess of the nodular sclerosing adolescent peak in Hodgkin's disease and its rapid fall with time is potentially of great importance. An even younger childhood peak of acute lymphoblastic leukemia is presented. Overall these data represent the most reliable available in the U.K., being population based, specially collected and will form the basis of considerable further investigations.

The age peak in childhood acute lymphoblastic leukemia: exploring the potential relationship with socioeconomic status

BACKGROUND

White children have a much higher incidence rate of acute lymphoblastic leukemia (ALL) than do African American children. This discrepancy, coupled with the geographic and temporal variations in the incidence of childhood ALL, have led to speculation that factors associated with socioeconomic status (SES) may play an important role in its etiology. Because most of the variation is accounted for by the occurrence of a peak in incidence between the ages of 2 and 5 years, the purpose of this study was to compare the SES of children diagnosed with ALL between the peak ages of 2-5 years with those children diagnosed at other ages (birth-1 year and 6-14 years).

METHODS

Patients included 4210 children who were diagnosed with ALL between January 1, 1989 and December 31, 1991 by a member institution of the Children's Cancer Group or the Pediatric Oncology Group. Of these children, 3614 were white and 596 were African American. The SES of a case was defined as the SES of the child's zip code of residence at the time of diagnosis. Five sociodemographic variable categories for each zip code were obtained from the 1990 U.S. Census including per capita income, number of housing units by household income, number of housing units by level of urbanization, number of persons older than 25 years by educational attainment, and number of persons by occupation. Mean values were compared for white children versus African American children, and peak ages (2-5 years) versus nonpeak ages (birth-1 year and 6-14 years) for both whites and African Americans. In addition, Wilcoxon's rank sum tests were performed.

RESULTS

There were statistically significant differences between the means in each of the socioeconomic categories when African Americans were compared with whites. However, within race, the means of the SES variables for white children diagnosed during the peak ages (2-5 years) were not significantly different from children diagnosed at other ages (birth-1 year and 6-14 years). Similarly, all but one of the comparisons for African American children yielded nonstatistically significant results. Similar results were obtained from the Wilcoxon's rank sum tests.

CONCLUSIONS

The results of this analysis suggest that age differences in childhood ALL incidence may not be solely accounted for by SES differences.

Pediatric cancer: environmental and genetic aspects

One in 600 children 0-16 years of age develop cancer, and 60% to 70% of them are cured. Projection of the data indicates that by the turn of the century, 1 of every 900 individuals between the ages of 16 and 44 years will be a cancer survivor. In the adult population, carcinogens and irradiation play a major role in oncogenesis. In the pediatric population other factors are probably dominant. Children of low socioeconomic groups, with nutritional deficiencies, are more exposed to viral infections at a very early age and have a greater chance of developing tumors such as Burkitt lymphoma or mixed cellularity Hodgkin disease. Other factors such as hormone-assisted conception or in vitro fertilization may have carcinogenic potential, although this has yet to be determined. Maternal diet during pregnancy, especially low folic acid consumption periconception, may have bearing on the fetus's risk of developing malignancy. The hazards of exposure to electric and magnetic fields from high-voltage transmission lines, home electric appliances, video display terminals, or residence near nuclear plants, although very doubtful, are included in the list of cancer promoters in children. Activated oncogenes, mutated suppressor genes, mismatch repair genes, nucleotide excision genes, and loss of imprinting genes are beginning to evolve as important factors in carcinogenesis. The more in-depth information on genetic and environmental factors should provide new data on the evolution of pediatric tumors and possibly on their prevention.

Childhood leukaemias in New Zealand: time trends and ethnic differences

Registrations from the New Zealand Cancer Registry were used to examine time trends in the incidence of leukaemias among children aged 0-14. There was a statistically significant increase in the incidence of leukaemia among children aged 0-4 during 1953-57 to 1988-90. In this age group, the recorded incidence rate increased from 4.89 per 100,000 person-years in 1953-57 to 7.92 in 1988-90. During 1973-77 to 1988-90 (and probably in earlier years), the increase was due to an increase in acute lymphoblastic leukaemia (ALL). The trends were unlikely to be due to changes in diagnosis or case ascertainment. The childhood leukaemia trends might be related to trends in family size, maternal age, socioeconomic level or exposure to infections. However, there are uncertainties about the importance of these factors or about their trends. The incidence of acute non-lymphoblastic leukaemia (ANLL) decreased between 1968-72 and 1988-90. The time trends highlight the likely importance of environmental factors in the aetiology of childhood leukaemias in New Zealand. The risk of ALL was lower in the Maori than in the non-Maori population (relative risk Maori/non-Maori 0.74). The risk of ANLL was higher among Maori (relative risk 1.84).

Survival of childhood leukemia in Singapore

The objective of this study was to evaluate the treatment outcome of children with acute leukemias at a university hospital in Singapore. Between January 1988 and January 1994, 66 children were treated, comprising 13 cases of acute myeloid leukemia (AML) and 53 acute lymphoblastic leukemia (ALL). The 2-year disease-free survival (DFS) was computed according to the Kaplan-Meier method. The results showed that the survival of AML was poor, with a 2-year DFS of only 30%. The major cause of death for AML was leukemia and leukemia-related complications, such as hemorrhage and severe infections. In contrast, a 62% 2-year DFS was achieved for ALL. It was found that marked hepatosplenomegaly (enlarged liver and/or spleen > or = 10 cm below the costal margin) at presentation correlated with a significance shortened survival in our patients with ALL. The major cause for treatment failure in ALL was recurrence of disease. We conclude that the DFS for our patients with ALL at 2 years was fair. The treatment results for AML were poor, but the numbers are too small to make any definite conclusions.

Characterization of acute lymphoblastic leukemia subtypes in Brazilian patients

The distribution of the acute lymphoblastic leukemia (ALL) subsets in 225 consecutive Brazilian patients was determined by an immunophenotypic study with an extensive panel of monoclonal antibodies. All subsets were detected and their relative frequencies were similar to those described in developed countries, except for the B-mature subset which had a higher frequency, especially in adults. Associated myeloid markers were expressed by 11% of the ALL and CD10 by 15.9% of T-ALL cases. Besides, the incidence rates determined for the region of Ribeirão Preto showed that the overall incidence of ALL was 12.5 cases/10(6) people years (PY) (5 cases/10(6) PY in non-Whites versus 14 cases/10(6) PY in Whites); the incidence of childhood ALL was 25.5 cases/10(6) PY (8.1 versus 29.8 cases/10(6) PY in non-Whites and Whites, respectively) and the incidence of ALL in adults was 6.2 cases/10(6) PY (5.5 versus 6.1 cases/10(6) Py in non-Whites and Whites, respectively). The significantly lower incidence rate of ALL in non-White children was associated with a selective deficit of the common subtype and a lack of the typical age peak of incidence in this group. The ALL features demonstrated here in Brazilian non-White children resemble those described in the American non-Whites before the seventies and those in British and American Whites at the beginning of the century.

Molecular analysis of HLA-DQB1 alleles in childhood common acute lymphoblastic leukaemia

Epidemiological studies suggest that childhood common acute lymphoblastic leukaemia (c-ALL) may be the rare outcome of early post-natal infection with a common infectious agent. One of the factors that may determine whether a child succumbs to c-ALL is how it responds to the candidate infection. Since immune responses to infection are under the partial control of (human leucocyte antigen) HLA genes, an association between an HLA allele and c-ALL could provide support for an infectious aetiology. To define the limit of c-ALL susceptibility within the HLA region, we have compared HLA-DQB1 allele frequencies in a cohort of 62 children with c-ALL with 76 newborn controls, using group-specific polymerase chain reaction (PCR) amplification, and single-strand conformation polymorphism (SSCP) analysis. We find that a significant excess of children with c-ALL type for DQB1*05 [relative risk (RR): 2.54, uncorrected P=0.038], and a marginal excess with DQB1*0501 (RR: 2.18; P=0.095). Only 3 of the 62 children with c-ALL have the other susceptibility allele, DPB1*0201 as well as DQB1*0501, whereas 15 had one or the other allele. This suggests that HLA-associated susceptibility may be determined independently by at least two loci, and is not due to linkage disequilibrium. The combined relative risk of the two groups of children with DPB1*0201 and/or DQB1*0501 is 2.76 (P=0.0076). Analysis of amino acids encoded by exon 2 of DQB1 reveal additional complexity, with significant (P<0.05) or borderline-significant increases in Gly26, His30, Val57, Glu66-Val67 encoding motifs in c-ALL compared with controls. Since these amino acids are not restricted to DQB1*0501, our results suggest that, as with DPB1, the increased risk of c-ALL associated with DQB1 is determined by specific amino acid encoding motifs rather than by an individual allele. These results also suggest that HLA-associated susceptibility to c-ALL may not be restricted to the region bounded by DPB1 and DQB1.

Viruses, clusters and clustering of childhood leukaemia: a new perspective?

Clusters of childhood leukaemia have, during a lengthy and controversial history, focussed attention on two alternative putative aetiological agents: infections and localised environmental pollution. In the United Kingdom emphasis is currently placed on the latter because of reports of localised clusters in the vicinity of two nuclear reprocessing plants. Now the most recent studies of spatial clustering in the United Kingdom also support the hypothesis that a substantial population of cases of childhood acute lymphoblastic leukaemia (ALL) arise as a rare host response to certain patterns of exposure to common infectious agents--the aberrant response model. Relevant aspects of the epidemiology of ALL are reviewed from this perspective and the hypothesis shown to be capable of unifying reported associations with different types of risk factor. It is probable that specific agent(s) are involved though none have been identified and these may share many epidemiological characteristics of herpes viruses. The possible relevance of these results to associations with prenatal parental occupational exposures to dusts and ionising radiation is explored.

Adult and childhood acute lymphocytic leukemia: are they different diseases?

Age has long been recognized as an important factor in predicting response to treatment for acute lymphocytic leukemia (ALL). Specifically, the results of treatment of childhood ALL have been far superior to the treatment of what appears to be the same disease in adults. However, from an analysis of the clinical and biological prognostic factors known to be predictive in childhood ALL, there is a striking difference in their distribution in adults with ALL. It appears that there is a special form of ALL seen in children of some populations with a peak incidence of three to seven years. This treatment responsive leukemia appears to be different clinically, biologically, and epidemiologically from adult ALL.

Correlation between car ownership and leukaemia: is non-occupational exposure to benzene from petrol and motor vehicle exhaust a causative factor in leukaemia and lymphoma?

Although there is widespread agreement that many cancers have environmental causes we are often unable to see associations between specific cancers and exposure to environmental chemicals. One might also speculate that the more widespread, common-place and 'normal' a chemical exposure is perceived to be then the less likely it will be that the exposure is recognised, let alone be considered to cause cancer. Widespread contamination of air by chemicals associated with internal combustion may be an example of one such 'invisible' carcinogenic exposure. Yet evidence is available which suggests that many leukaemia and lymphoma cases, as well as other cancers, may be caused by this mundane and ubiquitous environmental contamination. The hypothesis is developed that leukaemia 'clustering' as well as national leukaemia incidence may be related to non-occupational exposure to benzene formed by petrol combustion and resulting from petrol evaporation. The possible association between exposure to fuel vapours, internal combustion products and cancer merits much closer examination than it receives at present.

The age incidence of childhood acute lymphoblastic leukaemia

A mathematical model of childhood acute lymphoblastic leukaemia (ALL) is presented which is based on the assumptions that: 1) malignant clones of lymphoblasts arise by spontaneous mutation; 2) this is normally prevented by repair systems which either cause intracellular DNA repair or eliminate the malignant clone; and 3) the repair systems are fallible and their performance decays at random with time. If the major drive to lymphocyte division is microbial antigens then the model produces a reasonable fit to published data on the age distribution of ALL. Furthermore the model offers an explanation for the apparent increase in the incidence of ALL which is associated with improved social conditions.

Descriptive epidemiology of childhood leukaemia

Internationally there is a 4-fold variation in age-adjusted incidence rates for childhood leukaemia (all types combined), with only slightly greater worldwide differences specifically for acute lymphocytic leukaemia (ALL) and for acute nonlymphocytic leukaemia (ANLL). Total leukaemia rates are highest among Hispanic populations in Costa Rica and Los Angeles (males), due primarily to elevated ALL incidence, while low rates occur among US blacks, Kuwaitis, Israeli non-Jews, and Bombay Indians. In most populations the patterns for ALL are similar to those for total leukaema, with peak incidence at ages 1-4 and a decline thereafter. Lower and more uniform rates are generally observed at all ages for ANLL. Age-adjusted rates for ANLL appear to vary substantially among some populations with uniform ALL incidence rates (e.g., among Asians) and yet appear to be similar in other populations with variation in ALL rates (e.g., whites and blacks in the US). Possible variation among registries in completeness of childhood leukaemia ascertainment and accuracy of diagnosis by cell type should be assessed, while case-control investigations among populations with very high and very low rates may provide useful information about the cell-type specific determinants of childhood leukaemia.

Racial differences in acute lymphocytic leukemia mortality and incidence trends

Mortality and morbidity rates for childhood leukemia are examined with reference to time trends and racial differences. Prior to 1964, white and nonwhite children had very different acute lymphocytic leukemia (ALL) mortality rates. With the advent of successful chemotherapy, the mortality rate of ALL in white children has decreased resulting in virtually no racial differences in ALL mortality. The reasons for a stable ALL mortality rate in nonwhite children despite successful chemotherapy include poor access to health care, undefined socioeconomic factors and a biologically different type of ALL occurring in nonwhite children. Recent data from two cancer surveys (1969-1971, 1973-1976) reveal that nonwhite children have a lower incidence of ALL than white children. Underreporting in the nonwhite children could partly account for the difference, but other contributing factors might include a genetic predisposition, undefined socioeconomic influences, and perhaps, a viral agent. Further studies of the factors contributing to racial differences in ALL incidence and mortality are needed.

Trends in the incidence of childhood and adolescent cancer in Connecticut, 1935-1979

Trends in the incidence of childhood cancer in Connecticut are reported and analyzed for the period 1935-1979 by 5-year age groups (0-4, 5-9, 10-14, 15-19 years), using a log linear model method. A threefold increase (P less than .001) in the incidence of ALL in males 0-4 years of age was observed, with significant increases of smaller magnitude seen in males aged 5-9 and 15-19 and females aged 0-4 and 5-9. The incidence of central nervous system cancers also increased in several age groups for both sexes with the largest increase seen in males 0-4 years old. Significant increases in incidence of large magnitude were also observed for Hodgkin's disease, in males aged 15-19 years and females aged 10-19 years, for neuroblastoma in both sexes at ages 0-4 years, and for testis and ovarian cancer at ages 15-19 years. This study of trends in incidence of childhood cancers by 5-year age groups has revealed significant changes, which would not have been as apparent if broader age groups had been used. These results provide relevant data for investigating the etiology of cancer during infancy, childhood, and adolescence. Trends in Connecticut are compared with findings from other registries in the United States and other countries.

Review of cancer among 4 religious sects: evidence that life-styles are distinctive sets of risk factors

The occurrence of various types of cancer have been reviewed and evaluated in 4 religious groups. These patterns have been critically assessed in light of the distinctive life-style features of these groups. All 4 religious groups considered in this paper have reduced overall rates of cancer, suggesting that the life-styles of all 4 groups have merit in terms of reducing the overall risk of cancer. The rate of smoking among these groups is nearly nil, and the lung cancer rate in all 4 of these religious groups is strikingly low. Cancer of the oral structures, pharynx, larynx, and esophagus is also generally quite low. Amish and Hutterites have unusually high rates of breast cancer and juvenile leukemia. Reproductive factors frequently mentioned as risk factors for breast cancer cannot explain the excess breast cancer in the Amish and Hutterite women because they should have had the effect of reducing the rate. None of the numerous risk factors, normally suggested for leukemia, are consistent with this observation. The observations on ovarian cancer tend to confirm low parity and late age at first birth as risk factors, although the evidence is not entirely consistent. Also, contrary to common observations, the pattern of ovarian cancer contrasts greatly with the breast cancer pattern, suggesting dissimilar risk factors. Their low rate of cervical cancer is consistent with promiscuity being a strong risk factor, but other frequently suggested risk factors were generally inconsistent with the observations. Cancers of the stomach, colon, rectum, urinary bladder and prostate, in these 4 religious groups, are not readily explained by the risk factors commonly implicated in cancer of these sites. The patterns of a few types of cancers were consistent with the prevailing opinions of risk factors, but some cancers were poorly explained and, in some cases, the cancer patterns contradicted commonly held opinions concerning risk factors. Religions that provide strong directives for the personal lives of adherents result in distinctive life-style, reflecting multiple disease related factors (risk factors and protective factors). Disease related factors are related to each other in simple or more complex ways (e.g. additive, multiplicative or even more complex). Therefore, when dealing with distinctive life-styles, it may be unwarranted to attempt to isolate individual risk factors.

Comparison of trends in the incidence of multiple myeloma in Malmö, Sweden, and other countries, 1950-1979

Dramatic increases in mortality from multiple myeloma have been reported in the United States and the United Kingdom over the past three decades. To assess what fraction of this increase, if any, might be attributable to a change in the incidence of this disease, we examined the incidence of multiple myeloma during 1950 to 1979 in Malmö, Sweden, a city chosen because of its medical community's longstanding interest in this disease. The average annual incidence rates per 100,000 population were 4.9 for males and 3.7 for females (adjusted to the European age-standardized population). These rates are among the highest in the world. Unlike secular trends for myeloma in the United States and the United Kingdom, where large increases in mortality rates have been reported, the rates in Malmö have increased only slightly, and the increase was restricted to males, suggesting the possibility of environmental causes. We suggest that the rates in Malmö may represent the asymptote of myeloma's incidence that will be approached in other white populations as case ascertainment among them becomes complete.

Population-based age- and sex-specific incidence rates in the 4 main types of leukaemia

Due to recent developments in clinical haematology, 98.8% of all 1980 cases of leukaemia reported to the Danish Cancer Registry during the 4-year period 1973-76 could be subclassified into the 4 main types of leukaemia. Thus, it has been possible to characterize each of these types more accurately than before regarding age- and sex-specific incidence rates, relative frequency, male/female ratio, and median age at diagnosis. Chronic lymphatic leukaemia constituted 38% and chronic myeloid leukaemia 15% of the cases. These figures are larger and smaller, respectively, than these previously reported. The median age of all cases combined was 67 years, and the median age in cases of acute non-lymphocytic leukaemia was 64 years with 59% of the latter patients more than 60 years of age. In childhood myeloid leukaemia, an early incidence peak, not previously described, was observed before the age of 2 years. Analysis of Danish leukaemia incidence rates from 1943 and onwards shows no increase over 3 decades in patients less than 75 years of age. Thus, the observed increase in incidence from 5866-9942/100 000 during the period studied is limited to the very oldest age groups and is probably due to improved diagnostic efforts.

Thymus with B lymphocytes in chronic lymphocytic leukaemia

A 67-year-old man with a diagnosis of chronic lymphocytic leukaemia died suddenly following a coronary occlusion. Peripheral blood lymphocytes labelled with fluorescein conjugated polyvalent antisera to immunoglobulin and immunoglobulin G, and failed to label with absorbed antithymocyte serum. At necropsy, a large thymic tumour, and enlarged mediastinal lymph nodes also contained immunoglobulin G bearing B lymphocytes. The paradoxical finding of B lymphocytes with monoclonal surface immunoglobulin in a thymic mass is most unusual in chronic lymphocytic leukaemia.

Malignant disease of infancy and childhood with special reference to leukaemia: a survey of 6431 autopsy cases

A study on the prevalence of cancer at autopsy in Chilean children with special reference to leukaemia, was made. In a series of 15300 consecutive autopsies of Chileans, 70% of deceased patients had an autopsy. Of these 15300 cases (male:female ratio 1:0.92) 6431 were children (0-15 years of age); 90% of deceased children patients had an autopsy. The autopsy population of children and adults is a homogeneous ethnic group, and exhibits a low socioeconomic level. Data on the 6431 post-mortem examinations (1945-1966) came from the atuopsy records of five hospitals (four of them are teaching hospitals) in the city of Santiago. Each one of the leukaemia and solid tumour cases were diagnosed microscopically. In the children population, 54.92% were males and 45.08% were females. Of the 6431 autopsies, 142 exhibited cancer (2.21%), 2.43% being male cases and 1.93% being female cases. The autopsy cases showed a marked excess of boys (73.92%) and girls (69.77%) under 1 year of age. The prevalence of major morphological groups of cancer was as follows: leukaemias 50.70%, intracranial and other neural neoplasms 25.35%, malignant lymphomas, including Hodgkin's disease, 14.07%, and mixed malignant tumours (Wilms' tumour) 4.93%. 4.93%. Acute leukaemias (42.96%), medulloblastoma (7.65%), Hodgkin's disease (6.34%), Wilms' tumour (4.93%), and lymphosarcoma (4.93%) were the most prevalent types of cancer. Leukaemia cases had a corrected male:female ratio of 1:0.61. The prevalence of leukaemia in the atuopsy population was 1.12%.