[Cancer epidemiology after the Chernobyl accident]. / Epidémiologie de l'après-Tchernobyl.

The radioactive fallout from the Chernobyl accident, on 26 April 1986, has caused contamination of very wide areas of the northern hemisphere, in particular in Europe, causing chronic exposure of millions of people to a mixture of external and internal radiation. This paper summarizes the epidemiological studies published to date on the risks of cancer following the Chernobyl accident. An increase in the incidence of thyroid cancer observed among those exposed in childhood and adolescence in the most contaminated territories of Belarus, Russia and Ukraine is at present the only scientifically demonstrated radiation-related increase in cancer incidence. This observation provided important information on the risk of thyroid cancer related to 131I and on factors, such as iodine deficiency and stable iodine supplementation, which can modify this risk. The reports on increases in the incidence of other types of cancer are difficult to interpret because of methodological limitations. As the majority of these studies cover a relatively short time period, it is not possible to fully evaluate the radiological impact of the accident, and it is premature to draw conclusions on the risk of cancers other than that of thyroid. Predictions, based on the experience of other populations exposed to ionizing radiation, suggest that a substantial number of cancers could occur in Europe, especially in the most contaminated areas. Well-focused studies could verify these predictions, in particular with regard to the risks of leukaemia among liquidators and breast cancer among young women in the most contaminated areas.

Leukemia and exposure to ionizing radiation among German uranium miners.

BACKGROUND: It is well known that uranium miners are at an increased risk of lung cancer. Whether they also have an increased risk for other cancer sites remains under discussion. The aim of this study was to examine the leukemia risk among miners. METHODS: An individually matched case-control study of former uranium miners in East Germany was conducted with 377 cases and 980 controls. RESULTS: Using conditional logistic regression models, a dose-response relationship between leukemia risk and radon progeny could not be confirmed. Yet, a significantly elevated risk is seen in the category > or = 400 mSv when combining gamma-radiation and long-lived radionuclides. CONCLUSIONS: The results suggest that an elevated risk for leukemia is restricted to employees with a very long occupational career in underground uranium mining or uranium processing. Moreover, the study does not support the hypothesis of an association between exposure to short-lived radon progeny and leukemia risk.

Uranium-235 and childhood leukaemia around Greenham Common airfield.

There has been considerable publicity recently concerning the possible release of enriched uranium from the Greenham Common USAF base near Newbury in Berkshire. Evidence for the release relies on an internal report of the Atomic Weapons Research Establishment at Aldermaston, the authors of which postulated that it resulted from a fire in 1958 involving a B47 bomber standing on the runway. Their report contained a much publicised contour map of excess 235U levels estimated from the ratio of 235U to 238U in 26 evergreen leaf samples examined. The current concern of the inhabitants of Newbury centres mostly on the incidence of leukaemia, which was known beforehand to be slightly elevated in parts of West Berkshire, at least for young children. A number of cases have received considerable press publicity, with suggestions that their homes are located close to the base or the flight-path. The reports are, however, anecdotal and are not based on a complete register of cases. We have examined the evidence for this putative association by re-analysing the uranium data and determining the spatial relationship to the base of cases of childhood leukaemia diagnosed in the years 1966-87. We conclude that, although the excess uranium found has a non-random distribution, it does not support the pattern depicted by the contours and bears no relation to the incidence of childhood leukaemia for the period we examined. In any case, the increase in level of environmental radiation as a result of the putative release must be very small and is at variance with the reporting in some of the national press.

Treatment-related leukemia in breast cancer patients treated with fluorouracil-doxorubicin-cyclophosphamide combination adjuvant chemotherapy: the University of Texas M.D. Anderson Cancer Center experience.

PURPOSE: Adjuvant chemotherapy for breast cancer has been the routine practice in the past decade. A number of studies have observed an increased incidence of treatment-related leukemias following chemotherapy with alkylating agents and/or topoisomerase II inhibitors. We evaluated the incidence of treatment-related leukemias in breast cancer patients treated in four adjuvant and two neoadjuvant chemotherapy trials at The University of Texas M.D. Anderson Cancer Center. PATIENTS AND METHODS: Between 1974 and 1989, 1,474 patients with stage II or III breast cancer were treated in six prospective trials of adjuvant (n = 4) or neoadjuvant (n = 2) chemotherapy with fluorouracil, doxorubicin, and cyclophosphamide (CTX) (FAC) with or without other drugs. The median observation time was 97 months. In 1,107 patients, FAC chemotherapy was given postoperatively; 367 patients received induction chemotherapy, as well as postoperative chemotherapy. Eight hundred ten patients had surgery followed by radiotherapy and chemotherapy; 664 patients had surgery and chemotherapy only. Patients in two adjuvant and one neoadjuvant study received higher cumulative doses of CTX compared with those in the other studies. RESULTS: Fourteen cases of leukemia were observed. Twelve of these patients had received radiotherapy and chemotherapy, and two had received chemotherapy only. Six of the reported patients with leukemia were treated with a cumulative CTX dose of greater than 6 g/ m2. Five of these patients had received both radiotherapy and chemotherapy. The median latency period in the 14 patients was 66 months (range, 22 to 113). Six of 10 patients with adequate cytogenetic analyses had abnormalities that involved chromosomes 5 and/or 7. The rest of the patients had nonspecific cytogenetic abnormalities or lacked cytogenetic information. The 10-year estimated leukemia rate was 1.5% (95% confidence interval [CI], 0.7% to 2.9%) for all patients treated, 2.5% (95% CI, 1.0% to 5.1%) for the radiotherapy-plus-chemotherapy group, and 0.5% (95% CI, 0.1% to 2.4%) for the chemotherapy-only group; this difference was statistically significant (P = .01). The 10-year estimated leukemia risk for the higher-dose (> 6 g/m2) CTX group was 2% (95% CI, 0.5% to 5.0%) compared with 1.3% (95% CI, 0.4% to 3.0%) for the lower-dose group, a difference that was not statistically significant (P = .53). CONCLUSION: These data illustrate that patients treated with adjuvant FAC chemotherapy plus radiotherapy have a slightly increased risk of leukemia. This information needs to be considered in the treatment plans for patients with breast cancer. However, for most patients, the benefits of adjuvant therapy exceed the risk of treatment-related leukemia.

Magnetic healing, quackery, and the debate about the health effects of electromagnetic fields.

Although the biological effects of low-frequency electromagnetic radiation have been studied since the time of Paracelsus, there is still no consensus on whether these effects are physiologically significant. The recent discovery of deposits of magnetite within the human brain as well as recent, highly publicized tort litigation charging adverse effects after exposure to magnetic fields has rekindled the debate. New data suggest that electromagnetic radiation generated from power lines may lead to physiologic effects with potentially dangerous results. Whether these effects are important enough to produce major epidemiologic consequences remains to be established. The assumption of quackery that has attended this subject since the time of Mesmer's original "animal magnetism" investigations continues to hamper efforts to compile a reliable data base on the health effects of electromagnetic fields.

Cancer risk from the lifetime intake of Ra and U isotopes.

From extensive human data on the induction of skeletal cancers (bone sarcomas and carcinomas of the head sinuses) by 226Ra, 228Ra and 224Ra, the cumulative lifetime risk to 1 million people, each ingesting 5 pCi of a Ra isotope per day, was calculated to be nine bone sarcomas plus 12 head carcinomas for 226Ra, 22 bone sarcomas for 228Ra, and 1.6 bone sarcomas for 224Ra. Assuming that the risk per rad of average skeletal dose is equal for 226Ra and the U isotopes with half-lives exceeding 1000 yr and that the equilibrium skeletal content is 25 times the daily ingestion of 226Ra, but 11 times the daily ingestion of long-lived U, the cumulative life-span risk to 1 million persons, each ingesting 5 pCi per day of 233U, 234U, 235U, 236U or 238U, is estimated to be about 1.5 bone sarcomas. The U risk is not well established and additional research is needed on the metabolism of U in humans and its carcinogenicity in laboratory animals. These estimates assume linear dose responses. However, if incidence varies with the square of dose, virtually no induced cancers would be expected from these levels of radioactivity.