Garland Lecture. On the question of cancer induction by small X-ray doses

Is routine cardiac catheterization necessary in the management of patients with single ventricles across staged Fontan reconstruction? No!

With the advent of cardiac magnetic resonance imaging and high-resolution echocardiography, cardiac catheterization is unnecessary in clinical protocols in the "routine" single ventricle patient. Catheterization adds little to clinical care in these cases, and there are significant risks and costs associated with it. Catheterization should be reserved for cases in which noninvasive evaluations are equivocal, conflictory, demonstrate deterioration, or needed for intervention. This article delineates the role of noninvasive evaluations relative to cardiac catheterization in the routine single ventricle patient.

Hematologic consequences of exposure to ionizing radiation

From the early 1900s, it has been known that ionizing radiation (IR) impairs hematopoiesis through a variety of mechanisms. IR exposure directly damages hematopoietic stem cells and alters the capacity of bone marrow stromal elements to support and/or maintain hematopoiesis in vivo and in vitro. Exposure to IR induces dose-dependent declines in circulating hematopoietic cells not only through reduced bone marrow production, but also by redistribution and apoptosis of mature formed elements of the blood. Recently, the importance of using lymphocyte depletion kinetics to provide a "crude" dose estimate has been emphasized, particularly in rapid assessment of large numbers of individuals who may be exposed to IR through acts of terrorism or by accident. A practical strategy to estimate radiation dose and triage victims based upon clinical symptomatology is presented. An explosion of knowledge has occurred regarding molecular and cellular pathways that trigger and mediate hematologic responses to IR. In addition to damaging DNA, IR alters gene expression and transcription, and interferes with intracellular and intercellular signaling pathways. The clinical expression of these disturbances may be the development of leukemia, the most significant hematologic complication of IR exposure among survivors of the atomic bomb detonations over Japan. Those at greatest risk for leukemia are individuals exposed during childhood. The association of leukemia with chronic, low-dose-rate exposure from nuclear power plant accidents and/or nuclear device testing has been more difficult to establish, due in part to lack of precision and sensitivity of methods to assess doses that approach background radiation dose. Nevertheless, multiple myeloma may be associated with chronic exposure, particularly in those exposed at older ages.

Which paradigm for managing the risk of ionizing radiation?

This article tackles the problem of controversies expressed by experts in the field of estimating and managing ionizing radiation risks. We analyze the paradigms that were conceived on this subject, in particular the studies carried out by the International Commission on Radiological Protection (ICRP), as well as the papers stating either that the effect of low doses is relatively weak or, on the contrary, relatively serious. Uncertainties, which taint the risk estimations, assume a particular importance because they are at the origin of the request for expert and value judgments and represent the critical point of the discussions on the ionizing radiation risks. Our study allows us to look further into the problem of the paradigm's formation, uncertainties, and expert and value judgments, and provides areas for consideration that may contribute to a better understanding of certain gridlocks in the decision-making process, as regards to environmental, health, and energy policies.

The effects, risks, and guidelines for radiation use in orthopaedic surgery

Radiation is used during orthopaedic surgery in more than 15 million studies performed yearly. The biologic effects of radiation have been shown to inhibit mitosis by producing irrepairable deoxyribonucleic acid double strand breaks or create structural changes by damaging the nucleus, thereby producing potential genetic transmissions. Although human cells are thought to be resistant to malignant change and no studies have shown toxic effects resulting from long-term exposure to low-dose radiation, risks still are assumed. To decrease all risks, radiographic units should undergo periodic calibration, surgeons should wear protective devices, increase their working distance from the x-ray beam, and limit their duration of radiation exposure by making certain that they follow the guidelines set forth by the National Council for Radiation Protection and Measurement.

Screening for lung cancer. Another look; a different view

PURPOSE

There is widespread acceptance that screening for lung cancer is not indicated, to our knowledge, because no randomized trial has demonstrated a reduction in mortality as a result of screening. The objectives of this work are to review prospective studies on lung cancer screening and to analyze the extent to which known biases may have influenced observed results.

BACKGROUND

Four randomized controlled trials have been conducted. The Memorial-Sloan Kettering and Johns Hopkins Lung Projects compared annual chest radiographs (CXRs) in a control group with CXRs and sputum cytologic findings in an experimental group. Although both studies failed to demonstrate any difference in outcome by the addition of cytologic study to CXR, long-term survival in both studies was approximately three times that predicted by other data. Accordingly, these results are at least consistent with the hypothesis that the screening CXRs may have improved survival. Two randomized trials, the Mayo Lung Project and the Czechoslovak study, compared regular and frequent rescreening CXRs in an experimental group with sporadic and/or infrequent rescreening in a control group.

RESULTS

Both the Mayo and Czech studies demonstrated a striking advantage for screening with respect to stage distribution, resectability, survival, and fatality. Nevertheless, mortality was somewhat higher in the screened groups in both studies. Survival and fatality comparisons in randomized trials can be confounded by overdiagnosis bias, lead-time bias, and length bias, while mortality is not subject to these biases. Accordingly, it is believed that a mortality reduction represents the strongest evidence for screening efficacy. Mortality is directly proportional to cumulative incidence. In both the Mayo and Czech studies, incidence of lung cancer was higher in the screened group. The higher cumulative incidence (which in the Mayo Lung Project was statistically significant) made possible the discordant findings of superior survival/fatality and inferior mortality in the screened populations. Overdiagnosis has been widely accepted to account for the "missing cases" in the control populations in the Mayo and Czech studies. However, epidemiologic and autopsy evidence as well as an outcome analysis of unresected early-stage screen-detected lung cancer demonstrates that screening does not lead to the overdiagnosis of lung cancer. Similarly, lead-time bias and length bias cannot account for the outcome differences in the Mayo Lung Project or Czech study. If survival and fatality comparisons (which suggest a striking benefit from screening) are not biased, then mortality comparisons (which suggest no benefit) cannot accurately reflect lung cancer death rates in these trials. Population heterogeneity may provide an explanation for how outcome differences may have been misrepresented by mortality comparisons in these two trials, as well as other large population-based randomized studies.

CONCLUSIONS

Periodic screening CXRs lead to clinically meaningful improvements in stage distribution, resectability, survival, and fatality in lung cancer. Mortality reductions have not been demonstrated, but mortality did not accurately reflect lung cancer death rates in the Mayo Lung Project and Czechoslovak study. Accordingly, reconsideration of the desirability of periodic CXR screening may be appropriate for individuals at high risk of lung cancer.

Detection of breast cancer at a smaller size can reduce the likelihood of metastatic spread: a quantitative analysis

RATIONALE AND OBJECTIVES

The authors extrapolated the lognormal relationship between size of tumor and probability of metastasis to include small tumors.

METHODS

Extrapolation was performed by using linear weighted regression analysis techniques to estimate prediction intervals for the predicted probabilities.

RESULTS

Tumors detected at 1 cm in diameter had a 7.31% probability of metastasis (95% prediction interval [PI], 4.36% to 11.6%). Tumors detected at 5 mm in diameter had a 1.23% probability of metastasis (95% PI, 0.45% to 3.0%). Tumors detected at 2 mm had a 0.049% probability of metastasis (95% PI, 0.00705% to 0.267%).

CONCLUSION

This analysis shows a major reduction in metastasis probability when tumors are detected at small sizes. These results suggest that detection of very early tumors can substantially reduce the likelihood of metastatic spread.

Chest X-ray screening improves outcome in lung cancer. A reappraisal of randomized trials on lung cancer screening

It is believed that population-based screening for cancer should be advocated only when screening reduces disease-specific mortality. Four randomized controlled studies on lung cancer screening have been conducted in male cigarette smokers, and none has demonstrated reduced mortality. Accordingly, no organization that formulates screening policy advocates any specific early detection strategies for lung cancer. Yet, despite this public policy against screening, there is considerable evidence that chest x-ray screening is associated with earlier detection and improved survival. Two randomized trials, the Memorial Sloan-Kettering and Johns Hopkins Lung Projects, were specifically designed to evaluate the effectiveness of sputum cytologic study. Both evaluated the efficacy of the addition of sputum cytologic studies to annual chest radiographs, and both demonstrated that cytologic study did not favorably influence outcome. All individuals in experimental and control groups in both studies had annual chest radiographs. Because survival rates observed in both studies were about three times higher than predicted, based either on the National Cancer Institute's Surveillance Epidemiology and End Results database or based on the American Cancer Society's annual Cancer Statistics, raises the possibility that the periodic chest radiographs performed in all patients in both studies contributed to an improved outcome. In the Mayo Lung Project and in the Czechoslovak study on lung cancer screening, the experimental groups underwent a program of relatively intensive and regular rescreening with chest radiographs and sputum cytologic study, while the control groups underwent either less-frequent rescreening or no rescreening. In both studies, the screened groups achieved meaningful improvements in stage distribution, resectability, and survival. However, increases in cumulative incidence of lung cancer in the experimental group in both studies (which in the Mayo Lung Project reached statistical significance) prevented significant improvements in survival from translating into corresponding reductions in mortality. The possibility that screening may be associated with lung cancer "overdiagnosis" has been widely postulated to account for higher survival and incidence rates and equivalent mortality rates. However, analysis of autopsy information and of disease outcome in individuals with screen-detected early stage lung cancer who do not undergo surgical resection strongly supports the conclusion that screening does not lead to overdiagnosis of lung cancer. Similarly, lead-time and length bias do not adequately account for the differences in cumulative incidence observed in the Mayo and Czech studies.(ABSTRACT TRUNCATED AT 400 WORDS)

The iatrogenic leukaemias induced by radio- and/or chemotherapy

A short review, limited to recently published series of data, has been compiled on the 'therapy-induced' secondary malignancies. Their frequency, peak of incidence, haematological and clinical criteria, the influence of age, treated primary disease, choice of drug(s) and modality of prescription and the role of genetic and environmental factors are analyzed. The risk varies between 0.6 and 20.5% after different treatment forms. Some suggestions for the choice of treatment of chronic malignant disorders, and for the design of future epidemiological studies are given.

Outpatient radiographic exposure in the first five years of life

Young children receive a variety of diagnostic radiographs over time. In some cases the exposure to radiation may be unwarranted because the films may yield confusing results, or may also need to be repeated because of poor technical quality. Even when the results are clearly negative, the subsequent treatment may proceed as if the film had been positive because of the child's clinical condition. The cumulative effect of such low-dose radiation on infants and children over time is unknown. The number and types of outpatient radiographs received by a cohort of poor children from a hospital-based continuity clinic during their first 5 years of life were reviewed. Also noted were the reason for obtaining the film, whether it was positive for that reason or another, whether the child had a chronic condition that prompted the use of radiograph, and the child's sex, race, and age when the film was obtained. Of the 218 children, 132 (60.6%) received 349 sets of films in their first 5 years. There was no difference in the number of films by race or sex. Chest and posttrauma bone or joint films accounted for 315 sets of films or 90.3% of the total. Overall, 25.8% of the 267 chest films were positive; this varied by age. Only 15% of the chest films were positive in the first year compared with 29 to 49% in the second through fifth years (p less than 0.001). Cough was the respiratory symptom most reliably associated with a positive chest film, both for the cohort (p less than 0.0001) and for children in the first year of life (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Computed tomography evaluation of pheochromocytoma in pregnancy

Two cases representative of the spectrum of the problem of pheochromocytoma in pregnancy are presented. One patient was typical of many cases of pheochromocytoma not diagnosed until delivery, with resultant maternal and fetal death. Computed tomography accurately preoperatively localized a pheochromocytoma involving the organ of Zuckerkandl in the second patient, with subsequent uncomplicated removal of the tumor during a cesarean delivery. A discussion of pheochromocytomas in pregnancy and the relative risk and benefits of preoperative localization with computed tomography are presented.

Peripheral blood lymphocyte subsets in radiologists exposed to ionizing radiation

To investigate whether low dose ionizing radiation caused perturbation of peripheral blood lymphocytes in radiology unit staff, the T-helper/suppressor ratio was examined in eight radiologists exposed to low dose radiation over a period of 6 to 27 years (mean 12 years). No significant difference was noted in the T-cell subsets between exposed radiologists and non-exposed control subjects. The effect of low dose ionizing radiation on peripheral blood lymphocyte subsets seems to be virtually negligible. Further, measurement of the T-helper/suppressor ratio is not a reliable way of demonstrating any damage to bone marrow caused by low dose ionizing radiation.

Radiation exposure and protection in cardiac catheterization laboratories

Cardiac catheterization with angiography can deliver the greatest dose of x-radiation of any diagnostic medical examination. The physicians and technologists in the angiography room receive low-level scattered radiation over a period of months to decades. Although the radiobiology is complex, the physicians who perform cardiac catheterization should be familiar with the potential genetic and somatic effects of radiation and with the methods to reduce or eliminate x-ray exposure. The aim of radiation protection criteria is to reduce the risk of cancer death to less than the fatality risk for other occupations regarded as safe. This report is a review of the literature relating to radiation exposure and protection in cardiac catheterization laboratories. Catheterization personnel have control over the time duration of exposure, placement of technologists, shielding, location of equipment and monitoring of dose received.

How dangerous are diagnostic X-rays?

A review is made of the assessments of the magnitude of harm arising from diagnostic X-ray exposures. Factors influencing the effect of radiation are described. Financial values are estimated for the harm, both from carcinogenesis and genetic injury. The chance of injury to an individual patient is small and the number and type of examinations should be dictated by the clinical needs of the patient. An X-ray department is a safe place to work.

Analysis of risk in computerized tomography and other diagnostic radiology procedures

Medical practice entails continuous risks to the patient taken in good faith by the physician for the benefit of the patient. Risk of radiation induced cancer death approximates 10(-4) per cGy (rad). Assuming an average whole body dose of 0.1 cGy for many diagnostic X-ray procedures, the probability of radiation-induced cancer death is about 10(-5). The purpose of this paper is to compare the risks of common diagnostic X-ray procedures including computerized tomography (CT) with risks of smoking or automobile travel. Such comparisons should be constructive in putting radiation in perspective and facilitating explanation of risk/benefit to patients.