Cancer incidence in atomic bomb survivors. Part II: Solid tumors, 1958-1987

The risk of non-melanoma skin cancer incidence in the Japanese atomic bomb survivors

The latest Japanese atomic bomb survivor non-melanoma skin cancer incidence dataset is analysed and indicates substantial curvilinearity in the dose-response curve, consistent with a possible dose threshold of about 1 Sv, or with a dose-response in which the excess relative risk is proportional to the fourth power of dose, with a turning-over in the dose-response at high doses (> 3 Sv). The time distribution of the radiation-induced excess risk is best described by a model in which the relative excess risk is proportional to a product of powers of time since exposure and attained age. The fits of generalized relative risk models with exponential functions of time and age at exposure (and in particular of attained age) to adjust the relative risk are less satisfactory, as also are the fits of other models in which products of powers of time since exposure, age at exposure and attained age adjust the excess absolute risk. Sensitivity analyses indicate the importance of likely adjustments to the Hiroshima neutron doses for the optimal model parameters, particularly if values of the neutron relative biological effectiveness (RBE) of more than 5 are assumed. If adjustments recently proposed are made to the Hiroshima neutron doses, then using the optimal model (in which excess risk is proportional to the fourth power of dose) the best estimate of the neutron RBE is 1.3 (95% CI < 07.1). However, uncertainties in skin dose estimates for the atomic bomb survivors means that the findings with respect to the neutron RBE and the non-linearity in the dose-response curve should be treated with caution.

Late consequences of radioiodine for diagnosis and therapy in Sweden

With the exception of tobacco, ionizing radiation is probably the most studied carcinogen; however, it is not yet possible to determine whether a specific cancer was induced by radiation. Epidemiologic studies provide the primary data on cancer risk in humans after exposure to ionizing radiation. The present paper reviews the current epidemiologic knowledge on radiation-induced cancer, focusing on exposure to radioiodines, and describes the latest findings from the Swedish iodine cohorts.

Solid cancers after bone marrow transplantation

BACKGROUND

The late effects of bone marrow transplantation, including cancer, need to be determined in a large population at risk.

METHODS

We studied 19,229 patients who received allogeneic transplants (97.2 percent) or syngeneic transplants (2.8 percent) between 1964 and 1992 at 235 centers to evaluate the risk of the development of a new solid cancer. Risk factors relating to the patient, the transplant, and the course after transplantation were evaluated.

RESULTS

The transplant recipients were at significantly higher risk of new solid cancers than the general population (observed cases, 80; ratio of observed to expected cases, 2.7; P<0.001). The risk was 8.3 times higher than expected among those who survived 10 or more years after transplantation. The cumulative incidence rate was 2.2 percent (95 percent confidence interval, 1.5 to 3.0 percent) at 10 years and 6.7 percent (95 percent confidence interval, 3.7 to 9.6 percent) at 15 years. The risk was significantly elevated (P<0.05) for malignant melanoma (ratio of observed to expected cases, 5.0) and cancers of the buccal cavity (11.1), liver (7.5), brain or other parts of the central nervous system (7.6), thyroid (6.6), bone (13.4), and connective tissue (8.0). The risk was higher for recipients who were younger at the time of transplantation than for those who were older (P for trend <0.001). In multivariate analyses, higher doses of total-body irradiation were associated with a higher risk of solid cancers. Chronic graft-versus-host disease and male sex were strongly linked with an excess risk of squamous-cell cancers of the buccal cavity and skin.

CONCLUSIONS

Patients undergoing bone marrow transplantation have an increased risk of new solid cancers later in life. The trend toward an increased risk over time after transplantation and the greater risk among younger patients indicate the need for life-long surveillance.

Risk factors for primary breast cancer in Japan: 8-year follow-up of atomic bomb survivors

BACKGROUND

Findings from the Life Span Study (LSS) of the health effects of exposure to atomic bomb radiation have documented a strong dose-response relation between radiation exposure and breast cancer incidence.

PURPOSE

We analyzed data from the LSS cohort to identify nonradiation risk factors for breast cancer and to determine whether these factors were independent of the effects of radiation on breast cancer occurrence.

METHODS

Breast cancer incidence was ascertained among a cohort of 22,200 residents of Hiroshima and Nagasaki, Japan, who had completed a mail survey between 1979 and 1981 to study nonradiation risk factors for disease. During the subsequent follow-up period (average 8.31 years), 161 cases of primary breast cancer were identified through population-based tumor registries in the two cities.

RESULTS

The risk of breast cancer was inversely related to age at menarche and weakly positive in relation to age at menopause and years of menstruation. A significant negative association of full-term pregnancy against breast cancer was observed, although the number of pregnancies beyond the first was not related to the rate of breast cancer in the cohort. Women having their first full-term pregnancy before age 30 were at decreased risk of breast cancer relative to older women, but there was no trend. A nonsignificant, positive trend in risk was associated with increasing weight and body mass (kg/m2). The risk of breast cancer among women with a history of estrogen use was 1.64 (95% confidence interval 1.02-2.64) and with diabetes 2.06 (95% confidence interval 1.27-3.34). It was not possible to distinguish among additive and multiplicative models of the joint association of radiation dose and various non-radiation-related exposures (age at menarche, full-term pregnancy, female hormone preparations) identified in this analysis.

CONCLUSIONS

Nonradiation risk factors for breast cancer among Japanese atomic bomb survivors were consistent with those identified among other populations of women, although the prevalence of common risk factors was low. Reproductive factors and hormone use appear to act independently of radiation exposure on the risk of breast cancer among this population.

Gastrointestinal cancer after treatment of Hodgkin's disease

PURPOSE

This study aimed to quantify the risk of gastrointestinal cancer following Hodgkin's disease treatment according to age at treatment, type of treatment, and anatomic sites.

METHODS AND MATERIALS

Cases were identified from the records of 2,441 patients treated for Hodgkin's disease between 1961 and 1994. Follow-up averaged 10.9 years, representing 26,590 person-years of observation. Relative risks (RR) for gastrointestinal cancer incidence and mortality were computed by comparison with expected annualized rates for a general population matched for age, sex, and race.

RESULTS

Gastrointestinal cancers developed in 25 patients. The incidence RR was 2.5 [95% confidence interval (CI), 1.5-3.5] and mortality RR was 3.8 (CI, 2.4-4.7). Sites associated with significantly increased risks included the stomach [RR 7.3 (CI, 3.4-13.8)], small intestine [RR 11.6 (CI, 1.9-38.3)], and pancreas [RR 3.5 (CI, 1.1-8.5)]. Risk was significantly elevated after combined modality therapy, RR 3.9 (CI, 2.2-5.6). The risk after radiotherapy alone was 2.0 (CI, 1.0-3.4), not a statistically significant elevation. The RR for gastrointestinal cancer was greatest after treatment at young age and decreased with advancing age. It was significantly elevated within 10 years after treatment [RR 2.0 (CI, 1.1-3.5)] and increased further after 20 years [RR 6.1 (CI, 2.5-12.7)]. Risk assessed by attained age paralleled risk according to age at treatment. Fifteen cases of gastrointestinal cancers arose within the irradiation fields.

CONCLUSION

Patients treated for Hodgkin's disease are at modestly increased risk for secondary gastrointestinal cancer, especially after combined modality therapy and treatment at a young age. Risk was highest more than 20 years after treatment, but was significantly elevated within 10 years. Gastrointestinal sites with increased risk included the stomach, pancreas, and small intestine.

Head and neck radiation carcinogenesis: epidemiologic evidence

This article provides an overview of the long-term carcinogenic effects of medical radiation exposure to the head and neck and focuses on studies that allow risk quantification. The thyroid gland in children is extremely sensitive to the tumorigenic effects of external radiation for many years after exposure. Risk of thyroid cancer decreases with increasing age at exposure, with little risk, if any, apparent among persons exposed as adults. Large risks of neural tumors have been reported after moderate- and high-dose radiotherapy in childhood; however, the magnitude of the risk at low doses and for adult exposures is unclear. Data on salivary gland tumors are limited but tend to support an association with radiation exposure. In contrast, the pituitary gland appears to be relatively resistant to the tumorigenic effects of radiation. Several cohort studies have reported an increased risk of hyperparathyroidism among irradiated populations. In summary, radiation exposure to the head and neck can result in tumors of the thyroid, salivary, and parathyroid glands, as well as the brain and central nervous system.

Incidence of intracranial meningiomas in Nagasaki atomic-bomb survivors

Among the Nagasaki atomic-bomb survivors registered at the Scientific Data Center for Atomic-Bomb Disaster, Nagasaki University School of Medicine, 45 cases of surgically treated intracranial meningioma were collected from 6 hospitals with departments of neurosurgery in or near Nagasaki City during the period from 1973 to 1992. All 45 patients were over 40 years of age at the time of diagnosis. Subsequently, the 45 cases were statistically analyzed in relationship to the estimated distance from the hypocenter by age, gender, intracranial location, histology and latent period. The analysis showed a high correlation between incidence of meningiomas and distance from the hypocenter. The incidence among Nagasaki atomic-bomb survivors over 40 years of age, especially in those proximally exposed, appears to be increasing, in inverse proportion to the exposure distance, since 1981, 36 years after the explosion of the atomic bomb.

Evidence for curvilinearity in the cancer incidence dose-response in the Japanese atomic bomb survivors

The recently released data on cancer incidence in the Japanese atomic bomb survivors are analysed using a variety of relative risk models which take account of errors in estimates of dose to assess the dose-response at low doses. For all solid cancers analysed together there is a significant positive dose-response (at the one-sided 2.5% significance level) if all survivors who received < 0.5 Sv are considered, but the significance vanishes if doses of < 0.2 Sv are considered. If a relative risk model with a threshold (the dose-response being assumed linear above the threshold) is fitted to the solid cancer data, a threshold of more than about 0.2 Sv is inconsistent with the data, whereas these data are consistent with there being no threshold. Linear-quadratic models and linear-quadratic models with an exponential cell-sterilization term provide no better fit than the linear model. For the three main radiation-inducible leukaemia subtypes analysed together (acute lymphatic leukaemia, acute myeloid leukaemia and chronic myeloid leukaemia) there is a significant positive dose-response (at the one-sided 2.5% significance level) if all survivors who received < 0.5 Sv are considered, but the significance vanishes if doses of < 0.2 Sv are considered. If a relative risk model with a threshold (the dose-response being assumed linear above the threshold) is fitted to the leukaemia data, a thresh-old of more than about 0.3 Sv is inconsistent with the data. In contrast with the solid cancer data, the best estimate for the threshold level in the leukaemia data is significantly different from zero, even when allowance is made for a possible quadratic term in the dose-response, albeit at borderline levels of statistical significance (p = 0.04). There is little evidence for curvature in the leukaemia dose-response from 0.2 Sv upwards. However, the possible underestimation of the errors in the estimates of the dose threshold as a result of confounding and uncertainties not taken into account in the analysis, together with the lack of biological plausibility of a threshold, makes the interpretation of this finding questionable.

Phenotypic and functional characterisation of tumour-infiltrating lymphocytes derived from thyroid tumours

The natural history of thyroid tumours and the hyper-reactivity of the immune system in patients with thyroid cancer suggest that immune surveillance may play a role in the control of this disease. A study was therefore undertaken to analyse the phenotypic and functional features of tumour-infiltrating lymphocytes (TILs) derived from thyroid tumours. In a series of experiments, it was found that, in contrast to TILs derived from patients with melanoma or renal cell carcinoma, thyroid TILs could be efficiently expanded in vitro only in the presence of allogeneic EBV transformed B (B. EBV) cells. Indeed, only one of the seven thyroid-derived TILs grew in vitro without feeder cells, whereas all 16 thyroid-derived TILs could be expanded in the presence of allogeneic B. EBV feeder cells. Phenotypic analysis of these TILs revealed a frequent in vitro expansion of an unusual T cell population that expressed both the CD4 and CD8 markers. Indeed, it was demonstrated that in five of 14 TILs in short-term culture (< day 23) and four of 11 TILs in long-term culture (> day 40), a lymphocyte population that coexpressed CD4 and CD8 antigen accounted for more than 15% of the total TIL population. This double-positive T cell population was not observed in TILs derived from melanoma or renal cell carcinoma. Thyroid-derived TILs also displayed an intense cytolytic activity against NK-sensitive tumour targets with 10 of 11 TILs exhibiting significant cytotoxicity towards the NK-sensitive K562 cell line. Six of 11 TILs were also cytotoxic towards autologous tumour, but when cold target inhibition with K562 was performed with three cultures, unlabelled K562 completely inhibited lysis of autologous tumour cells. A significant expansion of CD3+CD56+ T cells in the different TIL populations may explain this high level of NK-like cytotoxicity. In conclusion, TILs derived from thyroid tumours could be efficiently expanded in vitro under certain culture conditions. Different strategies must be explored to enhance their specific tumour autologous specificity, however, before they can be used in immunotherapy protocols.

Lung carcinoma and malignant mesothelioma in patients exposed to Thorotrast: incidence, histology and p53 status

In a previous registry-based survey of 999 patients injected with alpha-emitting 232ThO2 (Thorotrast), we identified elevated risks for lung carcinoma and malignant mesothelioma. Since injected Thorotrast is retained lifelong mostly in liver, spleen and lymph nodes, the mesothelial surfaces of these organs are constantly irradiated. Thorotrast-administered patients also perpetually exhale 220Rn, a 232Th-daughter. Study of Thorotrast-exposed patients may, therefore, provide data with regard to carcinogenicity of radon exposure, a current public health concern, as well as the pathogenesis of malignant mesothelioma. The incidence and histologic types of lung carcinoma and malignant mesothelioma within the cohort were examined by review of available histopathologic material and medical records. Further, mutations of the p53 gene were analyzed whenever possible as it has previously been suggested that radon-associated lung carcinomas exhibit specific mutational patterns. The cumulative risk for lung carcinoma reached 11.0% based on 20 confirmed cases. Nine were small cell lung cancer (SCLC), whereas the expected frequency was 18%. The risk for malignant mesothelioma reached 2.5% based on 7 cases. The actuarial risk of malignant mesothelioma for patients given more than 20 ml Thorotrast was 7.8% compared to 1.4% for patients administered smaller amounts. Seven lung carcinomas and 5 malignant mesotheliomas were analyzed for p53 mutations; only 1 (in a lung adenocarcinoma) was detected. A possible association between Thorotrast and SCLC is suggested. In addition, a possible dose-response gradient exists for Thorotrast and malignant mesothelioma.

Late effects of radiation on the human immune system: an overview of immune response among the atomic-bomb survivors

The studies of the late effects of atomic-bomb (A-bomb) radiation on the immune system were started about 20 years after the bombings in 1945. The most remarkable late effects of radiation are the functional and quantitative abnormalities of T and B cells in survivors exposed to high doses (> or = 1.0 Gy). Abnormalities of T-cell immunity include (1) a decreased proportion of CD3+ T cells in peripheral blood lymphocytes, particularly the proportion of CD4+ CD45RA+ naive T cells (study period 1987-91); (2) an increased frequency of CD4- and CD8- (double negative) alpha beta + T cells (1987-91); and (3) functional defects in T-cell responses to mitogens and alloantigens (1974-85). B-cell abnormalities include: (1) a significant increase in the proportion of B cells among peripheral lymphocytes (1987-91); (2) an increase in serum immunoglobulin A levels in females and immunoglobulin M and the incidence of rheumatoid factor in both sexes (1987-89); and (3) an increased level of anti-Epstein-Barr virus antibody titer (1987-90). In contrast, suggestive (0.05 < p < 0.1) or not significant (p > 0.1) dose effects were observed for the number and function of natural killer cells (1983-91), and benign monoclonal gammopathy (1979-87). In addition, studies initiated sooner after the bombing such as the incidence of autoimmune diseases (1958-87), systemic bacterial infections (1954-67), and granulocyte functions (1947-79) also show little dose-effects. Thus, A-bomb radiation induced the alteration of the balance/interaction between the T- and B-cell subsets--specifically, a decrease in the T-cell population and an increase in the B-cell population in the periphery.

Normal genetic response to gamma irradiation in familial adenomatous polyposis

The present study, a co-operative project between three European institutes, was aimed at elucidating whether the APC gene in carriers of familial adenomatous polyposis coli (FAP) also causes some genetic sensitivity revealed by DNA damage and the yield of chromosome aberrations in peripheral blood lymphocytes exposed to gamma rays. In addition, it seemed of interest to study whether DNA repair is modified after irradiation of lymphocytes from FAP patients compared to controls. To this end, we have used the inhibition of the poly(ADP-ribose) polymerase (ADPRP) by 3-aminobenzamide (3ABA) and studied the effect of 3ABA on the frequency of DNA strand breaks and chromosome aberrations. The data indicate that FAP is not associated with an increased chromosomal sensitivity towards ionising radiation.

Second primary cancer after treatment for cervical cancer. An international cancer registries study

BACKGROUND

The pattern of second cancers after treatment for cervical cancer provides important information on the risk of radiation-induced malignancies. Large numbers of women survive many years and can be studied for late effects.

METHODS

Incident second cancers in 86,193 patients with cervical cancer reported to 13 population-based cancer registries in 5 countries were evaluated to estimate the risk of second cancer among very long term survivors.

RESULTS

Overall, 7543 second cancers were observed versus 6015 cancers expected based on population rates (observed/expected = 1.2). Lung cancer accounted for nearly half of the excess cancers. Among the 49,828 women treated with radiation, 3750 survived 30 or more years and a two-fold risk of cancers of heavily irradiated organs was seen. Most of the excess cancers were of the rectum, vagina, vulva, ovary, and bladder. Patterns of risk over time since treatment were consistent with a radiation etiology. Significant increases of nonchronic lymphocytic leukemia and cancers of the bone and kidney were also linked to radiotherapy. Women treated surgically were also at significant risk of second cancers, in all likelihood related to cigarette smoking and risk factors similar to those of cervical cancer.

CONCLUSIONS

Curative therapy for cervical cancer results in large numbers of long term survivors who develop second cancers very late in life. Radiation is an important cause of this increase and there is no evidence that risk returns to normal levels.

100 years of radiobiology: implications for biomedicine and future perspectives

The development of radiobiology from the very early detection of the biological action of X-rays to the knowledge of today is described in sections on radiation chemistry and biochemistry, mutation and cancer induction, and embryonic damage, as well as the dependence of radiation response on radiation quality and temporal dose distribution (repair) and the interaction with other factors. For medicine radiobiology serves as a basis for radiotherapy and radiological protection. The effect of very low doses, and their possible biopositive effect (hormesis and adaptive response), is also discussed, as are the health hazard of radon, health risks after the Chernobyl accident, and space radiobiology. The radiobiology of the future will be concerned with biomolecular and genetic implications, problems of damage and repair, and connected problems like hormesis.

Risk of solid tumors after irradiation in infancy

Cancer incidence was studied in 14,351 subjects exposed to ionizing radiation for skin hemangioma at the Radiumhemmet, 1920-1959. Record-linkage was done with the Swedish Cancer Registry for the period 1958-1986. After a mean follow-up of 39 years, 300 cancers were observed and the standardized incidence ratio (SIR) was 1.11 (95% confidence interval (CI) 0.99-1.24). The absorbed dose to different organs varied from < 0.01 Gy to > 40 Gy. The thyroid cancer incidence was significantly increased (SIR = 2.28; 95% CI 1.33-3.65) and for cancer of the breast SIR was 1.24 (95% CI 0.98-1.54). Regarding pancreatic cancer and tumors of the endocrine glands the statistically significantly increased SIRs were based on a small number of cases and might therefore only be a coincidence. No confirmed increased incidence could be established for other cancer sites.

A cohort study with regard to the risk of haematological malignancies in patients treated with x-rays for benign lesions in the locomotor system. I. Epidemiological analyses

Roentgen treatment for painful benign conditions in the locomotor system as arthrosis and spondylosis was in Sweden very common up to the beginning of the 1960s. The mode of treatment differed from the British ankylosing spondylitis series as smaller parts of the red bone marrow were exposed and smaller doses were applied. A cohort of 20,024 such patients treated 1950-1964 at two hospitals in northern Sweden was analysed with regard to the risk of haematological malignancies. Average factors for conversion of prescribed skin doses to mean absorbed red bone marrow doses were estimated on random samples of the different treatment sites and then applied on the cohort in its whole. The standard incidence ratio (SIR) for leukaemia was 1.18 (95% CI: 0.98-1.42) and the standard mortality ratio (SMR) 1.25 (0.99-1.45). In the highest dose group (mean absorbed red bone marrow dose > 0.5 Gy) the corresponding values were 1.40 (1.00-1.92) and 1.50 (1.08-2.04). In the mortality analysis also a slightly increased myeloma risk was noted with SMR = 1.20 (0.99-1.56). Extension of the cohort and nested case-control studies are under progress.