Effects of radiation on incidence of primary liver cancer among atomic bomb survivors.

We describe the radiation risk for primary liver cancers between 1958 and 1987 in a cohort of atomic bomb survivors in Hiroshima and Nagasaki, Japan. The analysis is based on a comprehensive pathology review of known or suspected liver neoplasms that generated 518 incident, first primary cases, mostly hepatocellular carcinoma. Excess relative risk from atomic bomb radiation was linear: 0.81 per sievert weighted liver dose (95% CI [0.32, 1.43]; P < 0.001). Males and females had similar relative risk so that, given a threefold higher background incidence in males, the radiation-related excess incidence was substantially higher in males. Excess risk peaked for those with age at exposure in the early 20s; there was essentially no excess risk in those exposed before age 10 or after age 45. Whether this was due to a difference in sensitivity or possible confounding by other factors could not be addressed retrospectively in the full cohort. A paucity of cholangiocarcinoma and hemangiosarcoma cases suggested that they are not significantly associated with whole-body radiation exposure, as they are with the internal alpha-particle-emitting radiological contrast medium Thorotrast. Because most of the radiation-related excess cases occurred among males, it is important to ascertain what factors put men at greater risk of radiation-related liver cancer.

Chernobyl-related thyroid cancer in children of Belarus: a case-control study.

The accident at the Chernobyl nuclear power plant on April 26, 1986, released approximately 2 EBq of 131I and other radioiodine isotopes that heavily contaminated southern Belarus. An increase in thyroid cancer reported in 1992 and attributed to the Chernobyl accident was challenged as possibly the result of intensive screening. We began a case-control study to test the hypothesis that the Chernobyl accident caused the increase in thyroid cancer. Records of childhood thyroid cancer in the national therapy centers in Minsk in 1992 yielded 107 individuals with confirmed pathology diagnoses and available for interview. Pathways to diagnosis were (1) routine endocrinological screening in 63, (2) presentation with enlarged or nodular thyroid in 25 and (3) an incidental finding in 19. Two sets of controls were chosen, one matched on pathway to diagnosis, the other representing the area of heavy fallout, both matched on age, sex and rural/urban residence in 1986. The 131I dose to the thyroid was estimated from ground deposition of 137Cs, ground deposition of 131I, a data bank of 1986 thyroid radiation measurements, questionnaires and interviews. Highly significant differences were observed between cases and controls (both sets) with respect to dose. The differences persisted within pathway to diagnosis, gender, age and year of diagnosis, and level of iodine in the soil, and were most marked in the southern portion of the Gomel region. The case-control comparisons indicate a strong relationship between thyroid cancer and estimated radiation dose from the Chernobyl accident.

Malignant mesothelioma: attributable risk of asbestos exposure.

OBJECTIVES: To evaluate a case-control study of malignant mesothelioma through patterns of exposure to asbestos based upon information from telephone interviews with next of kin. METHODS: Potential cases, identified from medical files and death certificates, included all people diagnosed with malignant mesothelioma and registered during 1975-1980 by the Los Angeles County Cancer Surveillance Program, the New York State Cancer Registry (excluding New York City), and 39 large Veterans Administration hospitals. Cases whose diagnosis was confirmed in a special pathology review as definite or probable mesothelioma (n = 208) were included in the analysis. Controls (n = 533) had died of other causes, excluding cancer, respiratory disease, suicide, or violence. Direct exposure to asbestos was determined from responses to three types of questions: specific queries as to any exposure to asbestos; occupational or non-vocational participation in any of nine specific activities thought to entail exposure to asbestos; and analysis of life-time work histories. Indirect exposures were assessed through residential histories and reported contact with family members exposed to asbestos. RESULTS: Among men with pleural mesothelioma the attributable risk (AR) for exposure to asbestos was 88% (95% confidence interval (95% CI) 76-95%). For men, the AR of peritoneal cancer was 58% (95% CI 20-89%). For women (both sites combined), the AR was 23% (95% CI 3-72%). The large differences in AR by sex are compatible with the explanations: a lower background incidence rate in women, lower exposure to asbestos, and greater misclassification among women. CONCLUSIONS: Most of the pleural and peritoneal mesotheliomas in the men studied were attributable to exposure to asbestos. The situation in women was less definitive.

Mortality follow-up of the 1942 epidemic of hepatitis B in the U.S. Army.

The hypothesis that adult infection with the hepatitis B virus in the United States leads to a carrier state with a high risk of primary liver cancer was tested in two ways: (a) a cohort mortality study of U.S. Army veterans given yellow fever vaccine contaminated with hepatitis B virus in 1942 and controls and (b) a case-control study comparing veterans with hepatocellular carcinoma in Veterans Affairs hospitals with matched controls with respect to receipt of contaminated vaccine in 1942. Three groups totaling 69,988 men were the subjects of the cohort study: group 1 comprised men hospitalized with hepatitis in 1942, group 2 comprised men subclinically infected in 1942 and group 3 comprised controls who entered service after the contaminated vaccine was discontinued. Hepatocellular carcinoma cases (n = 24) and control subjects (n = 63) derived from Veterans Affairs hospital discharge files were the subjects of the case-control study. Group comparisons of death rates from liver cancer were refined by expert review of records to select hepatocellular carcinoma from among all causes of death so diagnosed in the cohort study. Slightly excess mortality was found for hepatocellular carcinoma in group 2 (subclinical hepatitis B) but not for group 1 (overt hepatitis B) compared with group 3 (controls) (p = 0.08). Mortality from nonalcoholic chronic liver disease was less in group 2 than in group 3. In the case-control study, the relative risk for hepatocellular carcinoma conferred by receipt of contaminated vaccine was estimated as 3.3 (p = 0.06). We conclude from the cohort study that immunocompetent adult males rarely become carriers after hepatitis B virus infection, probably far less often than the frequently assumed rate of 5% to 10%. The small excess liver cancer mortality seen in the cohort study and the results of the case-control study are consistent, nevertheless, with the now well-established etiological role of hepatitis B virus infection in liver cancer.

Thyroid nodularity and chromosome aberrations among women in areas of high background radiation in China.

Thyroid nodularity following continuous low-dose radiation exposure in China was determined in 1,001 women aged 50-65 years who resided in areas of high background radiation (330 mR/yr) their entire lives, and in 1,005 comparison subjects exposed to normal levels of radiation (114 mR/yr). Cumulative doses to the thyroid were estimated to be of the order of 14 cGy and 5 cGy, respectively. Personal interviews and physical examinations were conducted, and measurements were made of serum thyroid hormone levels, urinary iodine concentrations, and chromosome aberrations in circulating lymphocytes. For all nodular disease, the prevalences in the high background and control areas were 9.5% and 9.3%, respectively. For single nodules, the prevalences were 7.4% in the high background area and 6.6% in the control area (prevalence ratio = 1.13; 95% confidence interval = 0.82-1.55). There were no differences found in serum levels of thyroid hormones. Women in the high background region, however, had significantly lower concentrations of urinary iodine and significantly higher frequencies of stable and unstable chromosome aberrations. Increased intake of allium vegetables such as garlic and onions was associated with a decreased risk of nodular disease, which seems consistent with experimental studies suggesting that allium compounds can inhibit tumor growth and proliferation. The prevalence of mild diffuse goiter was higher in the high background radiation region, perhaps related to a low dietary intake of iodine. These data suggest that continuous exposure to low-level radiation throughout life is unlikely to appreciably increase the risk of thyroid cancer. However, such exposure may cause chromosomal damage.

Studies of cancer among the Japanese A-bomb survivors.

Studies of cancer among the Japanese survivors of the A-bombs dropped on Nagasaki and Hiroshima are the major source of information on radiation carcinogenesis in humans. They have already made important contributions to the estimation of the risk of radiation-induced cancer and to our understanding of key factors influencing risk, especially tissue sensitivity, age at exposure, and the temporal distribution of radiogenic cancers. The size of the exposed population still surviving virtually guarantees the continued productivity of the research conducted in Hiroshima and Nagasaki. It should not be supposed, however, that these studies will ever provide all the information needed for radiation protection standards or risk estimation. The experience of the A-bomb survivors simply does not include all important aspects of radiation exposure for which information is needed. Moreover, despite the size of the sample remaining under study, it is most unlikely that direct, empirical estimates can be made that will remove the necessity for dependence upon mathematical models to derive estimates of risk in the low-dose region.

A serologic follow-up of the 1942 epidemic of post-vaccination hepatitis in the United States Army.

An epidemic of icteric hepatitis in 1942 affected approximately 50,000 U.S. Army personnel. This outbreak was linked to specific lots of yellow-fever vaccine stabilized with human serum. To identify the responsible virus and the consequences of the epidemic, during 1985 we interviewed and serologically screened 597 veterans who had been in the army in 1942. These subjects were selected from three groups. Group I consisted of patients who had received the implicated vaccine and had jaundice; Group II had received the implicated vaccine but remained well; Group III had received a new, serum-free vaccine, with no subsequent jaundice. Ninety-seven percent of Group I, 76 percent of Group II, and 13 percent of Group III were positive for antibodies to hepatitis B virus. Only one subject had hepatitis B surface antigen, for a carrier rate of 0.26 percent among recipients of the implicated vaccine. The prevalence of hepatitis A antibody was similar in all three groups, and no subject had antibody to hepatitis delta virus. We conclude that hepatitis B caused the outbreak, that about 330,000 persons may have been infected, that the hepatitis B virus carrier state was a rare consequence, and that the outbreak induced hepatitis B antibodies that appear to persist for life.

Recent trends in mesothelioma incidence in the United States.

Mesothelioma incidence rates based on data from population-based cancer registries in New York State (exclusive of New York City), Los Angeles County, California, and the SEER Program of the National Cancer Institute were analyzed for trends, using original cancer registry diagnoses. Results indicate a significant increase in incidence during 1973-80 for pleural mesothelioma among white males older than 55 at time of diagnosis but not for other age-race-sex-site subgroups. A histopathologic review of New York State and Los Angeles County cases by two independent pathologists, expert in the diagnosis of mesothelioma, lowered the overall estimates but a significant upward trend remained. The observed trend does not appear to be related to changes in diagnostic practice. The results of a five-member panel of expert pathologists will be published in a separate methodology paper.

Epidemiology of multiple sclerosis in US veterans: III. Migration and the risk of MS.

World War II or Korean Conflict veterans with MS (5,305 in number) and pre-illness-matched controls were compared for residence at birth and entry on active duty (EAD) within three north-south tiers of states in the United States. A strong north-south gradient of MS risk was present. Migrants were defined as those whose birth and EAD tier differed. For white men of World War II, all white men, and all whites, there were highly significant reductions in risk for moves southward from either the north or middle tier, and increases in risk for moves northward from the middle tier. Increases similar in magnitude of middle to north did not attain statistical significance in the few southern-born migrants. For the small groups of black men and white men of Korean service, trends were similar but did not attain significance, whereas for white women, they were of borderline significance. Findings imply an environmental cause for MS, with acquisition years before symptom-onset.

Chronic disease in the workplace and the environment. Record linkage: methodologic and legal issues.

Research on chronic disease arising from occupational exposure typically requires that events widely separated in time be linked through records created and maintained by more than one institution or agency. Too little attention is paid, in creating record forms, to the mechanics of record linkage and to the nature of the information needed for studies of the effect of the workplace on health. Record linkage also suffers from a highly decentralized federal statistical system and from changes in privacy legislation and in public attitudes toward personal privacy, changes motivated by invasions of privacy that have arisen from activities entirely unrelated to medical research. If medical research capabilities are to match the information needs of society a more adequate balance will have to be struck between those needs and personal privacy.

A methodologic assessment of radiation epidemiology studies.

Epidemiologic studies of the late effects of ionizing radiation have used the entire spectrum of situations in which man has been exposed. These studies have provided insights into the dependence of human effects upon not only dose to target tissues but also other dimensions of exposure, host characteristics, and time following exposure. Over the past three decades studies have progressed from the mere identification of effects to their measurement. Because investigators of human effects have no control over the exposure situation, validity must be sought in the consistency of findings among independent studies and with accepted biologic principles. Because exposure may be confounded with factors that are hidden from view, bias may enter into any study of human exposure. Avoidance of bias and attainment of sufficient power to detect relationships that are real--these are the methodologic challenges. Many methodologic issues, e.g. those associated with the definition and measurement of specific end points, or with the selection of appropriate controls, permeate epidemiologic work in all fields. Others, especially those concerned with the measurement of exposure, the patterning of events in time after exposure, and the prediction of events beyond the scope of existing observations--these give radiation epidemiology its distinctive character.

Epidemiology of multiple sclerosis in U.S. veterans: 2. Latitude, climate and the risk of multiple sclerosis.

An analysis of ten climatic factors and elevation for the counties of birth of 4371 U.S. white male veterans with multiple sclerosis and matched controls has been made in relation to birthplace latitude. The climatic factors include an air pollution index, concentrations of minerals in ground water, measures of annual solar radiation, both in energy per unit area and in hours of sunshine, mean annual periods of high and low temperatures, and measures of annual rainfall and average humidity. These variables all significantly influence the risk of multiple sclerosis when analyzed alone, but when they are adjusted for latitude, their effect is found to be due to their correlation with this variable.

The design of clinical studies to assess therapeutic efficacy in multiple sclerosis.

Poorly designed trials of therapy for multiple sclerosis (MS) can waste time and money, and may lead either to false hopes or to the overlooking of a potentially effective treatment. A well-designed trial may well develop useful scientific information even if the putative therapy fails to show any therapeutic effect. The diagnosis, clinical course, and definitions of the stages of MS are discussed as they relate to trials of therapy. The goals of such trials include favorable modification of an exacerbation, favorable modification or prevention of future exacerbations, effective treatment of the progressive stage, and improvement of function in the stable-deficit stage. There should be an orderly progression from a small preliminary trial to a modest pilot trial and, when indicated, a full trial. All types of trials require careful organization and management, appropriate selection of patients, and properly planned and recorded observations. The treatment contrast--how the new treatment will be evaluated--provides the essential structure of the trial. The hypothesis being examined, the treatment contrast, and the observations being made in the designed clinical trial will govern the form of the analysis and the nature of the interpretations. Each goal requires that specific strategies and design considerations be applied to preliminary, pilot, and full trials.