Cytogenetic and environmental factors in the etiology of the acute leukemias in adults

Cancer incidence and cause-specifi c mortality in male and female physicians: a cohort study in Estonia

Aims: To evaluate whether the presumed knowledge of physicians about healthier lifestyle decreases their risk of cancer and mortality, a retrospective cohort study of male and female physicians was conducted in Estonia. Methods: The cancer incidence and cause-specifi c mortality of 3,673 physicians (870 M, 2,803 F ) in Estonia was compared with the rates of the general population. Information on cancer cases and deaths in the cohort between 1983 and 1998 was obtained from the Estonian Cancer Registry and the mortality database of Estonia. Results: The standardized incidence ratio (SIR) for all cancers was 1.32 (95% confi dence interval (CI) 1.15-1.48) in women and 0.92 (95% CI 0.73-1.13) in men. Female physicians had an elevated risk for breast cancer (SIR 2.03, 95% CI 1.62-2.51) and myeloid leukaemia (SIR 3.69, 95% CI 1.35-8.02). Male physicians had an excess of skin melanoma (SIR 4.88, 95% CI 1.58-11.38). A large defi cit of lung cancer was observed (SIR 0.24, 95% CI 0.11-0.48). The very low all-cause mortality in the cohort (standardized mortality ratio 0.55, 95% CI 0.50-0.61) was mainly due to large defi cits in deaths from lung cancer, cardiovascular diseases and external causes. The suicide rate in the cohort was lower than in the general population. Conclusions: No health risks were observed in the cohort that could be linked to the occupational exposures of physicians. The pattern of cancer incidence and mortality seen in physicians in Estonia is similar to the pattern seen among professional classes in other countries.

Environmental nanoparticles are significantly over-expressed in acute myeloid leukemia

The increase in the incidence of acute myeloid leukemia (AML) may suggest a possible environmental etiology. PM2.5 was declared by IARC a Class I carcinogen. No report has focused on particulate environmental pollution together with AML. The study investigated the presence and composition of particulate matter in blood with a Scanning Electron Microscope coupled with an Energy Dispersive Spectroscope, a sensor capable of identifying the composition of foreign bodies. 38 peripheral blood samples, 19 AML cases and 19 healthy controls, were analyzed. A significant overload of particulate matter-derived nanoparticles linked or aggregated to blood components was found in AML patients, while almost absent in matched healthy controls. Two-tailed Student's t-test, MANOVA and Principal Component Analysis indicated that the total numbers of aggregates and particles were statistically different between cases and controls (MANOVA, P<0.001 and P=0.009 respectively). The particles detected showed to contain highly-reactive, non-biocompatible and non-biodegradable metals; in particular, micro- and nano-sized particles grouped in organic/inorganic clusters, with statistically higher frequency of a subgroup of elements in AML samples. The demonstration, for the first time, of an overload of nanoparticles linked to blood components in AML patients could be the basis for a possible, novel pathogenetic mechanism for AML development.

Mortality among a cohort of U.S. commercial airline cockpit crew

BACKGROUND

We evaluated mortality among 5,964 former U.S. commercial cockpit crew (pilots and flight engineers). The outcomes of a priori interest were non-chronic lymphocytic leukemia, central nervous system (CNS) cancer (including brain), and malignant melanoma.

METHODS

Vital status was ascertained through 2008. Life table and Cox regression analyses were conducted. Cumulative exposure to cosmic radiation was estimated from work history data.

RESULTS

Compared to the U.S. general population, mortality from all causes, all cancer, and cardiovascular diseases was decreased, but mortality from aircraft accidents was highly elevated. Mortality was elevated for malignant melanoma but not for non-chronic lymphocytic leukemia. CNS cancer mortality increased with an increase in cumulative radiation dose.

CONCLUSIONS

Cockpit crew had a low all-cause, all-cancer, and cardiovascular disease mortality but elevated aircraft accident mortality. Further studies are needed to clarify the risk of CNS and other radiation-associated cancers in relation to cosmic radiation and other workplace exposures.

Novel insights into etiologies of leukemia: a HuGE review and meta-analysis of CYP1A1 polymorphisms and leukemia risk

We conducted a meta-analysis to investigate the association of 2 single nucleotide polymorphisms in the cytochrome P450, family 1, subfamily 1A1 gene (CYP1A1), CYP1A1*2A and CYP1A1*2C, with the risk of developing different subtypes of leukemia in adults and children. A total of 26 studies published between 1999 and 2011 were identified by searching the PubMed, EMBASE, Medline, and Web of Science databases. The odds ratios for the CYP1A1 polymorphisms and leukemia risk were calculated. The cumulative evidence in genetic associations was graded by using the Venice criteria of the Human Genome Epidemiology Network (Atlanta, Georgia). The results showed that the cumulative evidence was moderate for the association of the CYP1A1*2A variant with leukemia in Caucasians and with childhood acute lymphoid leukemia in Caucasians. In addition, there was moderate evidence that children who carry both the CYP1A1*2A variant and the glutathione S-transferase M1 null genotype have an increased risk of acute lymphoid leukemia. For the CYP1A1*2C polymorphism, the cumulative evidence of an association with leukemia risk was moderate for adults and weak for children. Logistic regression analysis demonstrated an interaction between the CYP1A1*2C polymorphism and age. This meta-analysis showed that the CYP1A1*2A and CYP1A1*2C polymorphisms were associated with an increased risk of leukemia, and that the associations might vary by ethnicity, gene-gene interactions, age, and leukemia subtype.

Diet, lifestyle, and acute myeloid leukemia in the NIH-AARP cohort

The relation between diet, lifestyle, and acute myeloid leukemia was assessed in a US cohort of 491,163 persons from the NIH-AARP Diet and Health Study (1995-2003). A total of 338 incident cases of acute myeloid leukemia were ascertained. Multivariate Cox models were utilized to estimate hazard ratios and 95% confidence intervals. Compared with those for never smokers, hazard ratios were 1.29 (95% confidence interval: 0.95, 1.75), 1.79 (95% confidence interval: 1.32, 2.42), 2.42 (95% confidence interval: 1.63, 3.57), and 2.29 (85% confidence interval: 1.38, 3.79) for former smokers who smoked < or =1 or >1 pack/day and for current smokers who smoked < or =1 or >1 pack/day, respectively. Higher meat intake was associated with an increased risk of acute myeloid leukemia (hazard ratio = 1.45, 95% confidence interval: 1.02, 2.07 for the fifth vs. first quintile; P for trend = 0.06); however, there were no clear effects of meat-cooking method or doneness level. Individuals who did not drink coffee appeared to have a higher risk of acute myeloid leukemia than those who drank various quantities of coffee. Neither fruit nor vegetable intake was associated with acute myeloid leukemia. This large prospective study identified smoking and meat intake as risk factors for acute myeloid leukemia.

Cigarette Smoking and Acute Leukemia

Recent cohort and case-control studies have suggested that cigarette smoking may be involved in the etiology of leukemia. Rising trends have been observed for all leukemias when the amount of cigarettes smoked increased. However, the magnitude of the trend was strongest for myeloid leukemia. Although no detailed biological mechanism has been proposed, a causal link is made plausible by evidence of systemic effects of cigarette smoke and the presence in cigarette smoke of chemicals (benzene) and radioactive substances that have been associated with leukemia risk. Cigarette smoking has a deleterious effect on survival in leukemia by shortening complete remission duration and subsequent survival. The data reported in this review are derived from the medical literature and from the experience of the authors.

Acute Myeloid Leukemia: Epidemiology and Etiology

Although acute leukemias are infrequent diseases, they are highly malignant neoplasms responsible for a large number of cancer-related deaths. Acute myeloid leukemia (AML) is the most common type of leukemia in adults, yet continues to have the lowest survival rate of all leukemias. While results of treatment have improved steadily in younger adults over the past 20 years, there have been limited changes in survival among individuals of age >60 years [1, 2].

Acute myeloid leukemia: epidemiology and etiology

Acute myeloid leukemias (AMLs) are infrequent, yet highly malignant neoplasms responsible for a large number of cancer-related deaths. The incidence has been near stable over the last years. It continuously shows 2 peaks in occurrence in early childhood and later adulthood. With an incidence of 3.7 per 100,000 persons and an age-dependent mortality of 2.7 to nearly 18 per 100,000 persons, there is a rising awareness in the Western world of AML's special attributes resulting from an ever-aging population. To objectively describe epidemiologic data on this patient population, recent publications were evaluated to make transparent the current trends and facts. A review of the literature is presented, reflecting highlights of current research with respect to AML etiology. To estimate outcome and discuss informed treatment decisions with AML patients of different age groups and different biologic risk categories, it is mandatory to consider that the outcome results reported in clinical trials were until now heavily biased toward younger patients, whereas the overall dismal prognosis documented in population-based studies most likely reflects the exclusion of older patients from aggressive treatment. The etiology for most cases of AML is unclear, but a growing knowledge concerning leukemogenenic agents within chemotherapy regimens for other malignancies is already available. This includes specific associations of the most frequent balanced translocations in AML, including the "good-risk" abnormalities comprised by the core binding factor leukemias (i.e., AML with the translocation (8;21) and inversion of chromosome 16, and acute promyelocytic leukemia with the translocation (15;17)). In contrast to these genetic alterations, epigenetic lesions, e.g., promoter silencing by hypermethylation of the p15/INK4b and other genes, are increasingly recognized as important in the pathogenesis of AML.

Influence of cigarette smoking on the presentation and course of acute myeloid leukemia

BACKGROUND

It is known that cigarette smoking is associated with an approximately 50% increase in leukemia risk. In order to detect a possible influence of cigarette smoking on initial characteristics at the time of presentation and on the course of the disease, we conducted a retrospective study in 643 patients with newly diagnosed acute myeloid leukemia.

PATIENTS AND METHODS

The study comprised 339 males and 304 females (median age 59 years, range 18-84 years). Two hundred and ninety-six patients (46%), smoking at least one cigarette per day for 6 months, were considered as smokers, while 347 patients (54%) were non-smokers.

RESULTS

Cigarette smoking was significantly related to male gender (P <0.0001), professional occupancy (P = 0.002), presence of organomegaly (P = 0.01), and lower peripheral blood and bone marrow leukemic cell involvement (P = 0.007 and P = 0.0001, respectively). Leukemia of French-American-British (FAB) M1 subtype was more frequent in non-smokers (P = 0.005). Although not statistically significant, smokers tended to have lower leukocyte counts than non-smokers. No difference was noted in terms of complete remission rates between smokers and non-smokers (67% compared to 64%). However, a higher rate of severe pulmonary infection was observed in smokers during induction chemotherapy (P = 0.02). Cigarette smoking (>or=20 pack-years or smoking duration >or=30 years) was significantly associated with shorter disease-free survival (P = 0.03) and overall survival (OS; P = 0.02 and P = 0.004, respectively). Other characteristics associated with poor prognosis included mainly older age, unfavorable karyotype, secondary acute myeloid leukemia (AML) and elevated World Health Organization (WHO) performance status. Cigarette smoking was associated with shorter OS in younger adults, but did not significantly influence survival in patients >60 years old. Cigarette smoking worsened the poor OS in patients with unfavorable karyotype, but did not significantly influence the prognosis of other karyotypic risk groups. In a multivariate analysis, only karyotypic grouping and age remained of prognostic value for the occurrence of disease-free and overall survival.

CONCLUSIONS

Cigarette smoking has a deleterious effect on survival in AML by shortening complete remission duration and subsequent survival. It was associated with severe infections during aplasia. Leukemogenic compounds favoring complex karyotypic abnormalities could also be involved.

Acute myelogenous leukemia after exposure to strontium-89 for the treatment of adenocarcinoma of the prostate

BACKGROUND

Strontium-89 is a pure Beta-emitting radioactive analogue of calcium that has been shown to be beneficial in the palliation of pain due to osseous metastases from adenocarcinoma of the prostate. The most significant reported toxicity is dose-related, reversible, myelosuppression characterized primarily by thrombocytopenia.

METHODS

A report of two patients in whom acute myelogenous leukemia (AML) developed after treatment with strontium-89 and a review of the literature are presented.

RESULTS

The two patients described in the current study developed AML 17 months and 26 months, respectively, after exposure to strontium-89 for the treatment of prostate carcinoma. To the authors' knowledge these patients represent the first two reported cases of AML after strontium-89 therapy for prostate carcinoma.

CONCLUSIONS

The results of the current study suggest the leukemogenic potential of strontium-89 treatment in humans. To the authors' knowledge, the current study represents the first report of AML after therapeutic exposure to strontium-89. As this agent is used more frequently (and earlier in the disease course) in patients with prostate carcinoma, an increased incidence of secondary AML complicating the clinical management of patients with prostate carcinoma may be observed. [See editorial on pages 497-9, this issue.]

[Delayed effects of organochlorine pesticides in man]

Available information on organochlorines and the chronic effects of exposure to them are set out. Organochlorinated compounds are the most persistent pesticides and can be found in all ecosystems. Although they are generally efficient in pest control, they are also a potent environment pollutant and can provoke health problems in man. The evidences of the carcinogenic potential of organochlorines are controversial and insufficient, but they have been related to an increase in the incidence of some kinds of tumors, such as leukemia and solid tumors. Reproductive effects, due to anti-androgenic and estrogenic action, on embryonic virilization, the incidence of abortion and the frequency of prematurity, have also been observed. The accumulation of the organochlorines in the adipous tissue is positively correlated to the increase in aging and could be implicated in the development of aging diseases, such as Parkinson's disease. The effects of pesticides on human health have not yet been completely elucidated. Genotoxicity is one of the most serious of the possible harmful effects caused by these compounds and calls for special attention in view of the irreversible nature of the process and to the long latency associated with its manifestation.

Hematopoietic and lymphatic malignancies in vehicle mechanics

Although it is generally acknowledged that benzene causes leukemia, especially acute myeloid leukemia, considerable divergences persist in the assessment of the leukemia risk due to occupational low-level benzene exposure. Specifically, the risk for vehicle mechanics is considered by some authors as being nondetectable with epidemiologic methods, whereas others calculated that the incidence rate of leukemia (all types) in vehicle mechanics is increased more than 60 times. The purpose of this review is to examine the publications on this topic in light of criteria for causal inference and to discuss the possible role of bias, confounding factors, and chance. The results of this analysis reveal that there are surprisingly few epidemiologic observations supporting an increased incidence of leukemia in vehicle mechanics. Apparently, publications suggesting a leukemogenic effect of low-level benzene exposure in garage mechanics are more often quoted than their negative counterparts, although they are not better designed.

Acute lymphoblastic leukemia. A comprehensive review with emphasis on biology and therapy

BACKGROUND

Acute lymphoblastic leukemia (ALL) is the most common malignancy in children. It is now curable in 60-70% of children. Most of the current understanding of the biology and treatment of ALL originates from studies of children. In adults, although much progress has been achieved, ALL is curable in only 20-35% of patients.

METHODS

A review of the biology and treatment of ALL from the English literature was performed.

RESULTS

Immunophenotypic and cytogenetic analyses of ALL have contributed to a more rational classification of ALL. These analyses have identified subgroups with poor prognosis or with different therapeutic requirements. Overall, 60-70% of adults with ALL have poor prognostic features, including older age, a high leukocyte count, non-T-cell immunophenotype, Ph-positive genotype, and longer time to achieve a complete remission. These patients have a cure rate of 20-25%, whereas those without these risk factors, have a 60-70% probability of survival. The use of more intensive induction regimens with growth factor support may improve survival rates. Also, intensive consolidation-intensification may improve survival rates. Most patients benefit from maintenance therapy, but the dose schedule must be optimized. Central nervous system (CNS) prophylaxis is beneficial, particularly for patients with a high risk for CNS relapse and when introduced early during induction of remission. Patients with high risk characteristics may benefit from allogeneic bone marrow transplantation (BMT) during first remission, and all other patients may benefit from it during first or subsequent relapse. Autologous BMT may be a valuable option for poor compliant patients.

CONCLUSIONS

Although the prognosis of patients with ALL has improved markedly during the past decades, newer strategies, including more dose-intensive therapy, the search for new drugs, and more target-specific therapy, are needed to improve the current cure rates.

Acute leukemia and residential proximity to potential sources of environmental pollutants

Possible associations between location of residence and acute leukemia risk were investigated in a study of 610 newly diagnosed patients, aged 18-79 y, and 618 population controls. There was an association between ever living within 5 miles (8 km) of an industrial plant and leukemia risk, with adjusted odds ratios (ORs) of 1.4 (95% confidence interval [95% CI] = 1.0-1.9) for all acute leukemias combined, 1.4 (95% CI = 1.0-2.0) for acute myeloid leukemia, and 1.7 (95% CI = 1.0-2.7) for acute lymphocytic leukemia. Odds ratios increased with decreasing distance from industrial sites, but a gradient with duration of residence was seen only among those less than age 60 who had lived within a mile of any industry. Suggestive associations were also observed for residence near specific industries, but the number of individuals living near any one industry was small.

Distinct cytogenetic and clinicopathologic features in acute myeloid leukemia after occupational exposure to pesticides and organic solvents

BACKGROUND

To study the correlation of environmental exposure to potentially mutagenic agents and the clinicopathologic picture in acute myeloid leukemia (AML), clinical features, morphologic characteristics, immunophenotype, and cytogenetics were studied in 59 patients with newly diagnosed AML.

METHODS

Based on interviews on occupational hazards and hobbies showing prolonged contact with pesticides (18 patients) and organic solvents (7 patients), 25 patients were categorized as "exposed". Thirty-four patients were categorized as "unexposed,", based on anamnestic findings.

RESULTS

Light microscopic studies showed myelodysplasia involving multiple cell lineages in all assessable patients with professional exposure to pesticides and organic solvents, whereas morphologic aberrations of the non-blast cell population were confined to a minority of cells in unexposed patients. These findings were confirmed by electron microscopic studies in 31 patients. Immunologic analysis showed the presence of a minor megakaryoblastic component in six exposed patients and showed positive findings for the CD34 stem cell marker in 85% of exposed patients, a figure significantly higher as compared with that for unexposed subjects. Cytogenetic studies confirmed the frequent occurrence of 5q and/or 7q aberrations in patients occupationally exposed (10 of 25 cases). Other recurring chromosome aberrations in the exposed group were 17p-, trisomy 11q, and translocation of 16q, 6p, 7p, and 11p, whereas the classic AML-specific translocations (i.e., t[15;17]; t[8;21]) were detected only in unexposed subjects. Conventional chemotherapy achieved complete remission in 1 of 19 exposed patients, as opposed to 14 of 29 unexposed patients, with a median survival of 2 months in the former group and 8 months in the latter.

CONCLUSIONS

Taken together, these findings document that AML in patients professionally exposed to toxic substances may represent a distinct cytogenetic and clinicopathologic entity. The clinicobiologic characteristics in these exposed patients are similar to the features of AML arising in patients with prior chemotherapy for another tumor, thus suggesting that similar transformation pathways may underlie leukemogenesis induced by cytotoxic drugs and by environmental exposure to some pesticides or organic solvents.

[Tobacco and leukemia]

Although some epidemiological studies have published findings supporting the hypothesis that smokers are at a higher risk of developing leukemia, the causal relationship between tobacco and leukemia has not been considered conclusive due to the weak association found, to the lack of a dose-response relationship and to the inconsistencies found throughout the different studies. However, most of these studies were not specifically designed to establish the tobacco-leukemia relationship and therefore their capacity to evaluate this hypothesis is rather limited. This hypothesis could be supported by the fact that tobacco causes cancer in sites which are not in direct contact with tobacco smoke. Likewise, the presence of benzene and radioactive compounds would provide some biologic plausibility to the hypothesis that tobacco could be a cause of leukemia. However, since the etiology of leukemia is not well understood, the small excess risk detected may be confounded by some uncontrolled factor.

Occupation and leukemia mortality among men in 16 states: 1985-1987

The relationship between leukemia and occupation was investigated in a case-control study using death certificates of 5,147 men who died of leukemia (ICD-9 codes 204-208) and 51,470 who died of other causes in 16 U.S. states from 1985 to 1987. Of six occupational activities identified previously as potentially increasing the risk of leukemia, only petroleum refining and rubber manufacturing had excess deaths for all leukemias combined (odds ratios (ORs) = 1.3, 95% confidence intervals (CI) = 0.6-2.8 and 0.9-1.8, respectively). Meat workers and wood workers had elevated mortality from acute lymphocytic leukemia (OR = 2.2, 95% CI = 0.7-7.0 and OR = 1.3, 95% CI = 0.8-2.2, respectively). There was no leukemia excess among farmers or auto mechanics. A survey of 43 other occupational groups indicated a widespread excess of leukemia among white collar occupations, primarily managers and professionals, but none among blue collar workers. This pattern was most pronounced for men under 65 years of age, and existed for all leukemia subtypes and among both blacks and whites. Despite the lack of specific exposure information and other limitations of death certificate data, these results encourage further examination of occupational causes of leukemia.

Occupational history and involvement of chromosomes 5 and 7 in acute nonlymphocytic leukemia

We compared the histories of exposure to leukemogens for two groups of patients presenting with myelodysplastic syndrome (MDS) or acute nonlymphocytic leukemia (ANLL). In one group there were 59 patients with an acquired abnormality of chromosomes 5 or 7 in the marrow at time of diagnosis. In the other group there were 39 patients with a normal marrow karyotype at the time of diagnosis. A much higher proportion of the chromosomally abnormal cases had a history of treatment for a previous malignancy (odds ratio = 13.0, p less than 0.01). There was little difference found between the occupational histories of the patients with de novo ANLL with and without cytogenetic abnormalities. An occupational history of exposure to chemicals or metals was more common in males with either a deletion of the long arm of chromosome 7 or with monosomy 7 or monosomy 5 (82.3%) than in males with a normal karyotype (52.1%). The odds ratios did not, however, reach statistical significance.

Minnesota Highway Maintenance Worker Study: cancer mortality

Highway maintenance workers (HMWs) have been exposed to a broad range of potentially toxic substances, including diesel fuels and exhaust, asphalts and tars, herbicides, gasoline, polynuclear aromatic hydrocarbons, benzene, and lead. The number of current and former state, county, and municipal HMWs in the United States exceeds 500,000, yet the health risks of this occupation had never been studied. To fill this void and to respond to the public perception that Minnesota HMWs were at high risk of developing leukemia, an occupational cohort mortality study was conducted of Minnesota HMWs employed between 1945 and 1984. Leukemia mortality in HMWs with 30-39 years of work (standardized mortality ratio [SMR] = 425; 95% confidence interval [CI] = 171-876) and urologic cancer mortality in HMWs with 40-49 year latency (SMR = 292; CI = 117-602) were significantly elevated. The extent to which these and other findings were directly related to work exposures is unknown. Further investigations to resolve the significance of the risks associated with the HMW occupation are currently underway.