BREAST CANCER FOLLOWING MULTIPLE FLUOROSCOPIES

Science-informed Policy Making for Protecting People and the Environment from Radiation

ABSTRACT

The process to arrive at the radiation protection practices of today to protect workers, patients, and the public, including sensitive populations, has been a long and deliberative one. This paper presents an overview of the US Environmental Protection Agency's (US EPA) responsibility in protecting human health and the environment from unnecessary exposure to radiation. The origins of this responsibility can be traced back to early efforts, a century ago, to protect workers from x rays and radium. The system of radiation protection we employ today is robust and informed by the latest scientific consensus. It has helped reduce or eliminate unnecessary exposures to workers, patients, and the public while enabling the safe and beneficial uses of radiation and radioactive material in diverse areas such as energy, medicine, research, and space exploration. Periodic reviews and analyses of research on health effects of radiation by scientific bodies such as the National Academy of Sciences, National Council on Radiation Protection and Measurements, United Nations Scientific Committee on the Effects of Atomic Radiation, and the International Commission on Radiological Protection continue to inform radiation protection practices while new scientific information is gathered. As a public health agency, US EPA is keenly interested in research findings that can better elucidate the effects of exposure to low doses and low dose rates of radiation as applicable to protection of diverse populations from various sources of exposure. Professional organizations such as the Health Physics Society can provide radiation protection practitioners with continuing education programs on the state of the science and describe the key underpinnings of the system of radiological protection. Such efforts will help equip and prepare radiation protection professionals to more effectively communicate radiation health information with their stakeholders.

Fluoroscopy X-Ray Organ-Specific Dosimetry System (FLUXOR) for Estimation of Organ Doses and Their Uncertainties in the Canadian Fluoroscopy Cohort Study

As part of ongoing efforts to assess lifespan disease mortality and incidence in 63,715 patients from the Canadian Fluoroscopy Cohort Study (CFCS) who were treated for tuberculosis between 1930 and 1969, we developed a new FLUoroscopy X-ray ORgan-specific dosimetry system (FLUXOR) to estimate radiation doses to various organs and tissues. Approximately 45% of patients received medical procedures accompanied by fluoroscopy, including artificial pneumothorax (air in pleural cavity to collapse of lungs), pneumoperitoneum (air in peritoneal cavity), aspiration of fluid from pleural cavity and gastrointestinal series. In addition, patients received chest radiographs for purposes of diagnosis and monitoring of disease status. FLUXOR utilizes age-, sex- and body size-dependent dose coefficients for fluoroscopy and radiography exams, estimated using radiation transport simulations in up-to-date computational hybrid anthropomorphic phantoms. The phantoms include an updated heart model, and were adjusted to match the estimated mean height and body mass of tuberculosis patients in Canada during the relevant time period. Patient-specific data (machine settings, exposure duration, patient orientation) used during individual fluoroscopy or radiography exams were not recorded. Doses to patients were based on parameter values inferred from interviews with 91 physicians practicing at the time, historical literature, and estimated number of procedures from patient records. FLUXOR uses probability distributions to represent the uncertainty in the unknown true, average value of each dosimetry parameter. Uncertainties were shared across all patients within specific subgroups of the cohort, defined by age at treatment, sex, type of procedure, time period of exams and region (Nova Scotia or other provinces). Monte Carlo techniques were used to propagate uncertainties, by sampling alternative average values for each parameter. Alternative average doses per exam were estimated for patients in each subgroup, with the total average dose per individual determined by the number of exams received. This process was repeated to produce alternative cohort vectors of average organ doses per patient. This article presents estimates of doses to lungs, female breast, active bone marrow and heart wall. Means and 95% confidence intervals (CI) of average organ doses across all 63,715 patients were 320 (160, 560) mGy to lungs, 250 (120, 450) mGy to female breast, 190 (100, 340) mGy to heart wall and 92 (47, 160) mGy to active bone marrow. Approximately 60% of all patients had average doses to the four studied organs of less than 10 mGy, 10% received between 10 and 100 mGy, 25% between 100 and 1,000 mGy, and 5% above 1,000 mGy. Pneumothorax was the medical procedure that accounted for the largest contribution to cohort average doses. The major contributors to uncertainty in estimated doses per procedure for the four organs of interest are the uncertainties in exposure duration, tube voltage, tube output, and patient orientation relative to the X-ray tube, with the uncertainty in exposure duration being most often the dominant source. Uncertainty in patient orientation was important for doses to female breast, and, to a lesser degree, for doses to heart wall. The uncertainty in number of exams was an important contributor to uncertainty for ∼30% of patients. The estimated organ doses and their uncertainties will be used for analyses of incidence and mortality of cancer and non-cancer diseases. The CFCS cohort is an important addition to existing radio-epidemiological cohorts, given the moderate-to-high doses received fractionated over several years, the type of irradiation (external irradiation only), radiation type (X rays only), a balanced combination of both genders and inclusion of people of all ages.

EPIDEMIOLOGY OF BREAST CANCER IN UKRAINE WITH CONSIDERATION OF THE FACTORS OF THE CHORNOBYL ACCIDENT

OBJECTIVE

Assessment of the possible impact of the Chornobyl accident on the incidence of breast cancer in the female population of Ukraine as a whole and in some affected groups.

OBJECT OF THE STUDY

The female population of Ukraine as a whole and in separate groups of victims - women par- ticipating in the clean-up works in 1986-1987, evacuaees from the exclusion zone and inhabitants of the territo- ries most contaminated with radionuclides.

METHODS

Statistical, mathematical, cartographic.

RESULTS

This study, covering a significant period of time (1976-2016), revealed a steady temporal and territorial agglomeration of regions with a higher incidence of breast cancer in the southern and south-eastern regions of Ukraine. Lower - in the western and northern regions. There is a steady increase in the incidence rate, but in recent years this growth has slowed down. The epidemiological situation regarding the incidence of breast cancer in the female population of Ukraine during the 30 years after the Chornobyl accident is generally stable. At the same time, a marked increase in the frequency of this pathology in the groups of the affected population, especially in women, participated in clean-up works in 1986-1987.

CONCLUSIONS

A stable agglomeration of regions with high levels of incidence in the south and south-east, and low in the west and north of the country is determined. The dynamics of breast cancer in Ukraine as a whole is characterized by steady growth, although in recent years its pace has slightly decreased. Among the individual population groups affected by the Chornobyl catastrophe (female liquidators, evacuated women from the exclusion zone, residents of the most contaminated with radionuclides territories) only among female liquidators of 1986-1987 the significant in- crease was observed in the incidence of breast cancer, which exceeds the national indicators at 1.3-1.6 times.

Organ-specific dose coefficients derived from Monte Carlo simulations for historical (1930s to 1960s) fluoroscopic and radiographic examinations of tuberculosis patients

This work provides dose coefficients necessary to reconstruct doses used in epidemiological studies of tuberculosis patients treated from the 1930s through the 1960s, who were exposed to diagnostic imaging while undergoing treatment. We made use of averaged imaging parameters from measurement data, physician interviews, and available literature of the Canadian Fluoroscopy Cohort Study and, on occasion, from a similar study of tuberculosis patients from Massachusetts, United States, treated between 1925 and 1954. We used computational phantoms of the human anatomy and Monte Carlo radiation transport methods to compute dose coefficients that relate dose in air, at a point 20 cm away from the source, to absorbed dose in 58 organs. We selected five male and five female phantoms, based on the mean height and weight of Canadian tuberculosis patients in that era, for the 1-, 5-, 10-, 15-year old and adult ages. Using high-performance computers at the National Institutes of Health, we simulated 2,400 unique fluoroscopic and radiographic exposures by varying x-ray beam quality, field size, field shuttering, imaged anatomy, phantom orientation, and computational phantom. Compared with previous dose coefficients reported for this population, our dosimetry system uses improved anatomical phantoms constructed from computed tomography imaging datasets. The new set of dose coefficients includes tissues that were not previously assessed, in particular, for tissues outside the x-ray field or for pediatric patients. In addition, we provide dose coefficients for radiography and for fluoroscopic procedures not previously assessed in the dosimetry of this cohort (i.e. pneumoperitoneum and chest aspirations). These new dose coefficients would allow a comprehensive assessment of exposures in the cohort. In addition to providing newly derived dose coefficients, we believe the automation and methods developed to complete these dosimetry calculations are generalizable and can be applied to other epidemiological studies interested in an exposure assessment from medical x-ray imaging. These epidemiological studies provide important data for assessing health risks of radiation exposure to help inform the current system of radiological protection and efforts to optimize the use of radiation in medical studies.

State of the evidence 2017: an update on the connection between breast cancer and the environment

BACKGROUND

In this review, we examine the continually expanding and increasingly compelling data linking radiation and various chemicals in our environment to the current high incidence of breast cancer. Singly and in combination, these toxicants may have contributed significantly to the increasing rates of breast cancer observed over the past several decades. Exposures early in development from gestation through adolescence and early adulthood are particularly of concern as they re-shape the program of genetic, epigenetic and physiological processes in the developing mammary system, leading to an increased risk for developing breast cancer. In the 8 years since we last published a comprehensive review of the relevant literature, hundreds of new papers have appeared supporting this link, and in this update, the evidence on this topic is more extensive and of better quality than that previously available.

CONCLUSION

Increasing evidence from epidemiological studies, as well as a better understanding of mechanisms linking toxicants with development of breast cancer, all reinforce the conclusion that exposures to these substances - many of which are found in common, everyday products and byproducts - may lead to increased risk of developing breast cancer. Moving forward, attention to methodological limitations, especially in relevant epidemiological and animal models, will need to be addressed to allow clearer and more direct connections to be evaluated.

Comparison of Contrast Volume, Radiation Dose, Fluoroscopy Time, and Procedure Time in Previously Published Studies of Rotational Versus Conventional Coronary Angiography

Conventional coronary angiography (CA) with static imaging is limited by the ability to properly select the optimal acquisition angle, vessel foreshortening, and significant radiation exposure. Rotational coronary angiography (RA) acquires coronary images in a multitude of viewing angles during a single injection by means of a moving gantry that rapidly completes a predefined arc. This study compares procedural characteristics of CA and RA. Electronic search of databases such as OVID, Medline, and PubMed was conducted to identify studies comparing procedural characteristics of CA and RA. End points for analysis included contrast volume, radiation dose by dose area product, radiation dose by air kerma, fluoroscopy time, and procedure time. Studies were assessed for quality and bias and were included if they compared coronary imaging of both the right and left coronary systems with CA and RA, included one of the end points of interest, and were in English. A total of 11 studies consisting of 940 patients who underwent RA and 976 who underwent CA were included in the final analysis. Contrast volume, radiation dose by dose area product, and radiation dose by air kerma were all found to be significantly lower with RA compared with CA. There was a statistically significant increase in fluoroscopy time, although this was not clinically significant, and there was no difference in procedure time. RA angiography is a feasible alternative to CA and offers reductions in contrast used and radiation exposure.

Medical imaging using ionizing radiation: optimization of dose and image quality in fluoroscopy

The 2012 Summer School of the American Association of Physicists in Medicine (AAPM) focused on optimization of the use of ionizing radiation in medical imaging. Day 2 of the Summer School was devoted to fluoroscopy and interventional radiology and featured seven lectures. These lectures have been distilled into a single review paper covering equipment specification and siting, equipment acceptance testing and quality control, fluoroscope configuration, radiation effects, dose estimation and measurement, and principles of flat panel computed tomography. This review focuses on modern fluoroscopic equipment and is comprised in large part of information not found in textbooks on the subject. While this review does discuss technical aspects of modern fluoroscopic equipment, it focuses mainly on the clinical use and support of such equipment, from initial installation through estimation of patient dose and management of radiation effects. This review will be of interest to those learning about fluoroscopy, to those wishing to update their knowledge of modern fluoroscopic equipment, to those wishing to deepen their knowledge of particular topics, such as flat panel computed tomography, and to those who support fluoroscopic equipment in the clinic.

The quality factor of x-rays/gamma rays as one is realistic?

The quality factor for x-rays, gamma rays and electrons assigned as one need to be revised. It is observed that as the energy decreases, mean lethal radiation dose (Do)decreases as well and become more potent. It is therefore proposed that radiation quality in biological systems should be assessed in the mitotic phase of the cell cycles. Furthermore, based on the mean lethal radiation dose within specific energy range, an appropriate quality factor of x-rays, gamma rays and electrons should be assigned.

Toward a holistic approach in the presentation of benefits and risks of medical radiation

Frequently messages are conveyed about benefit and risk in medical imaging or in imaging-guided medical intervention that are quite different from the intended communication. This is because communication is not merely the words used to express an idea. The message involves many personal factors on the part of the communicator and on the part of the audience. The intent of this article is to disclose some of the underlying factors that disproportionately bias communication of benefit and risk. Suggestions on how to develop a holistic communication of benefits and risks are presented. It is recommended that communication about the application of radiation to patients be disassociated from standard radiation protection concepts. The medical profession should develop unique communication tools to deliver a message that focuses on benefit/risk as a holistic entity, not benefit or risk as separate entities.

Lauriston S. Taylor lecture: radiation epidemiology--the golden age and future challenges

Epidemiology is the study of the distribution and causes of disease in humans. Studies of human populations exposed to ionizing radiation have been conducted for nearly 100 y during the "Golden Age of Radiation Epidemiology." Radiation epidemiology is now so sophisticated that human studies are the basis for radiation protection standards and for compensation schemes in response to claims of ill health from prior exposures. The studies of exposed human populations are very broad and include not only the Japanese atomic bomb survivors, but also patients given radiotherapy for cancer, patients treated with radiation for nonmalignant disease, patients given diagnostic radiation, persons with intakes of radionuclides, workers exposed to occupational radiation, and communities exposed to environmental sources of radiation. But there is more to be learned, and future knowledge may be advanced from new and continued occupational studies of the early radiation workers, atomic veterans, medically exposed patients, and populations living in areas of high natural background radiation. The interaction between radiation and underlying genetic susceptibilities is an important emerging area of research. It is indeed an honor to be included among the Lauriston S. Taylor Lecturers.

Survival and radiation risk in patients obtaining more than six CT examinations during one year

BACKGROUND

During a review of the current practice for computer tomography (CT) in 2005 at the Department of Radiology, Aarhus University Hospital, we observed 300 patients with more than six CT examinations during one year. They comprised 8% of the patients and accounted for 27% of all examinations. These patients needed further analysis.

MATERIAL AND METHODS

The 300 patients were analyzed concerning age, type of diseases indicating multiple CTs and the CT protocols used. The effective dose and risk of low dose radiation was estimated and survival of the patients after >1.5 year was analyzed.

RESULTS

A total of 289 patients had malignancies, the most frequent being lung cancer, bladder cancer and colon cancer. A total of 4.3% of the patients with malignancies were < or =40 year old, 13.3% were 41-50 years old and 62.7% 51-70 years old. The highest average number of CT examinations was observed in patients with sarcomas (11.2 examinations per patient). Eleven patients (aged 15-77 years) had traumatic lesions. Their number of examinations varied from 7 to 20. The total radiation dose for all 300 patients was 21.42 Sv, which may imply induction of a fatal cancer in one of the patients. However, only 102 patients survived their disease.

CONCLUSION

A total of 198 patients had serious disease and were not alive 1.5 years after the examinations. The multiple CT examinations were necessary to monitor their treatment. For the surviving 102 patients the use of CT contributed to an optimal therapy, but the examinations implied a risk for radiation induced malignancies.

Review of relative biological effectiveness dependence on linear energy transfer for low-LET radiations

Information on Japanese A-bomb survivors exposed to gamma radiation has been used to estimate cancer risks for the whole range of photon (x-rays) and electron energies which are commonly encountered by radiation workers in the work place or by patients and workers in diagnostic radiology. However, there is some uncertainty regarding the radiation effectiveness of various low-linear energy transfer (low-LET) radiations (x-rays, gamma radiation and electrons). In this paper we review information on the effectiveness of low-LET radiations on the basis of epidemiological and in vitro radiobiological studies. Data from various experimental studies for chromosome aberrations and cell transformation in human lymphocytes and from epidemiological studies of the Japanese A-bomb survivors, patients medically exposed to radiation for diagnostic and therapeutic procedures, and occupational exposures of nuclear workers are considered. On the basis of in vitro cellular radiobiology, there is considerable evidence that the relative biological effectiveness (RBE) of high-energy low-LET radiation (gamma radiation, electrons) is less than that of low-energy low-LET radiation (x-rays, betas). This is a factor of about 3 to 4 for 29 kVp x-rays (e.g. as in diagnostic radiation exposures of the female breast) and for tritium beta-rays (encountered in parts of the nuclear industry) relative to Co-60 gamma radiation and 2-5 MeV gamma-rays (as received by the Japanese A-bomb survivors). In epidemiological studies, although for thyroid and breast cancer there appears to be a small tendency for the excess relative risks to decrease as the radiation energy increases for low-LET radiations, it is not statistically feasible to draw any conclusion regarding an underlying dependence of cancer risk on LET for the nominally low-LET radiations.

Unilateral and bilateral breast cancer in women surviving pediatric Hodgkin's disease

PURPOSE

To define demographic and therapeutic associations with the risk of breast cancer in children treated for Hodgkin's disease (HD), particularly the frequency and interval to the development of contralateral breast cancer.

METHODS AND MATERIALS

All 398 female patients (<19 years) treated for HD in five institutions during the accrual period were evaluated. Mean follow-up was 16.9 years. The standardized incidence ratio (SIR) was calculated as the ratio of the observed number of cases to the expected number of cases, estimated using age-matched controls from the Surveillance, Epidemiology, and End Results database.

RESULTS

A total of 29 women developed breast cancer (25 invasive, 4 ductal carcinoma in situ; SIR, 37.25; 95% confidence interval, 24.96-53.64). Time to diagnosis was 9.4 to 36.1 years. Cumulative incidence was 24% at 30 years. Ten patients (34%) had bilateral disease (9 metachronous, 1 synchronous). The interval to contralateral breast cancer was 12 to 34 months. On univariate analysis, significant variables included stage of HD, mantle radiation dose, pelvic radiation (protective), and follow-up time. On multivariate analysis, early stage and older age at diagnosis of HD (<or=12 vs. >12 years) were significant predictors of secondary breast cancer.

CONCLUSIONS

Women surviving pediatric HD were found to have a 37-fold increase in the risk of breast cancer and a high likelihood of rapidly developing bilateral disease. Early-stage HD and age greater than 12 years at diagnosis of HD were independent risk factors. Higher radiation doses may augment risk, and pelvic radiation may be protective. Breast cancer screening methodology and frequency, plus the role of prophylaxis in patients with unilateral disease, require definition.

[Epidemiologic data on radiation-induced breast cancer]

BACKGROUND

Female breast cancer is the most frequent cancer, both in incidence and mortality. It is well known that exposure to ionizing radiation increases the risk, but some questions remain concerning low dose and low-dose rate effects and cofactors. These potential effects have to be taken into account to carry out adequate risk assessment on medically exposed populations. A literature review is proposed on this issue.

METHODS

A Medline search was undertaken. Keywords used were ionizing radiation, breast cancer and epidemiology. More studies were added through references included in the first list of articles. The focus was placed on studies including quantitative dose-effect relationship analyses.

RESULTS

A latency of five to 10 to 13 years is observed in the appearance of risk. The risk diminishes with age at exposure. A diminution with age at risk is also suspected. The excess relative risk per gray varies between 0.3 and 1.5 for an age at first exposure of 25 years. The study of Hiroshima and Nagasaki survivors shows that risk is increased even if doses are restricted to below 0.5Gy. Above high doses (20Gy), the risk no longer increases. This can be interpreted as a cell-killing effect. The excess subsists if doses are fractionated, but a diminution of the effect is suspected.

CONCLUSION

The effects of exposure to levels of doses used for medical diagnostic are very difficult to study in the general population by epidemiological methods. Only studies conducted on very young children could achieve enough power, because of their high radiosensitivity. Available information on the effects of doses above 0.5Gy allows extrapolation on maximal effects. Models deduced from existing cohorts can be used to assess risk, with their limits due to associated uncertainties. Preston et al. proposed an excess absolute-risk model, which makes estimates from the more comprehensive cohorts compatible. This model has been retained by the 2006 committee "Biological effects of ionizing radiation" (report VII).

Cancer risks from diagnostic radiology

In recent years, there has been a rapid increase in the number of CT scans performed, both in the US and the UK, which has fuelled concern about the long-term consequences of these exposures, particularly in terms of cancer induction. Statistics from the US and the UK indicate a 20-fold and 12-fold increase, respectively, in CT usage over the past two decades, with per caput CT usage in the US being about five times that in the UK. In both countries, most of the collective dose from diagnostic radiology comes from high-dose (in the radiological context) procedures such as CT, interventional radiology and barium enemas; for these procedures, the relevant organ doses are in the range for which there is now direct credible epidemiological evidence of an excess risk of cancer, without the need to extrapolate risks from higher doses. Even for high-dose radiological procedures, the risk to the individual patient is small, so that the benefit/risk balance is generally in the patients' favour. Concerns arise when CT examinations are used without a proven clinical rationale, when alternative modalities could be used with equal efficacy, or when CT scans are repeated unnecessarily. It has been estimated, at least in the US, that these scenarios account for up to one-third of all CT scans. A further issue is the increasing use of CT scans as a screening procedure in asymptomatic patients; at this time, the benefit/risk balance for any of the commonly suggested CT screening techniques has yet to be established.

Pediatric CT research elevates public health concerns: low-dose radiation issues are highly politicized

This article presents an analysis of issues related to low-dose radiation, with a focus on pediatric computed tomography (CT). It references several early studies that are seldom quoted in radiation research papers, then quantifies the excess lifetime fatal cancer yield attributable to an estimated 6.5 million pediatric abdominal CT scans. The authors highlight an important policy document issued jointly by the National Cancer Institute and the Society for Pediatric Radiology--specifically, its conclusion that a small dose from CT represents "a public health concern." Finally, the article identifies several contentious issues and proposes policy initiatives that, if implemented, could result in significant reductions of future radiogenic cancers and chronic injuries. The authors call for discussions between professional radiology societies and public interest health organizations, thereby involving all stakeholders.

Medical radiation exposure and breast cancer risk: findings from the Breast Cancer Family Registry

Moderate to high-dose radiotherapy is known to increase the risk of breast cancer. Uncertainties remain about the effects of low-dose chest X-rays, particularly in individuals at increased genetic risk. We analyzed case-control data from the Breast Cancer Family Registry. Self-reported data on therapeutic and diagnostic radiation exposures to the chest were available for 2,254 breast cancer cases and 3,431 controls (1,556 unaffected sisters and 1,875 unrelated population controls). We used unconditional logistic regression analyses to estimate odds ratios (OR) and 95% confidence intervals (CI) associated with radiation exposure, after adjusting for age, study center, country of birth, and education. Increased risks for breast cancer were found for women who had radiotherapy for a previous cancer (OR=3.55, CI=1.47-8.54) and diagnostic chest X-rays for tuberculosis (OR=2.49, CI=1.82-3.40) or pneumonia (OR=2.19, CI=1.38-3.47). Risks were highest for women with a large number of exposures at a young age or exposed in earlier calendar years. There was no evidence of increased risk associated with other diagnostic chest X-rays (not including tuberculosis or pneumonia), both in women with and without indicators of increased genetic risk (i.e., diagnosed at age <40 years or family history of breast cancer). Given the widespread and increasing use of medical diagnostic radiation, continued surveillance of breast cancer risk is warranted, particularly in women at specific genetic risk, such as those carrying mutations in BRCA1 or BRCA2.

Increased standardized incidence ratio of breast cancer in female electronics workers

BACKGROUND

In 1994, a hazardous waste site, polluted by the dumping of solvents from a former electronics factory, was discovered in Taoyuan, Taiwan. This subsequently emerged as a serious case of contamination through chlorinated hydrocarbons with suspected occupational cancer. The objective of this study was to determine if there was any increased risk of breast cancer among female workers in a 23-year follow-up period.

METHODS

A total of 63,982 female workers were retrospectively recruited from the database of the Bureau of Labor Insurance (BLI) covering the period 1973-1997; the data were then linked with data, up to 2001, from the National Cancer Registry at the Taiwanese Department of Health, from which standardized incidence ratios (SIRs) for different types of cancer were calculated as compared to the general population.

RESULTS

There were a total of 286 cases of breast cancer, and after adjustment for calendar year and age, the SIR was close to 1. When stratified by the year 1974 (the year in which the regulations on solvent use were promulgated), the SIR of the cohort of workers who were first employed prior to 1974 increased to 1.38 (95% confidence interval, 1.11-1.70). No such trend was discernible for workers employed after 1974. When 10 years of employment was considered, there was a further increase in the SIR for breast cancer, to 1.62. Those workers with breast cancer who were first employed prior to 1974 were employed at a younger age and for a longer period. Previous qualitative studies of interviews with the workers, corroborated by inspection records, showed a short-term high exposure to chlorinated alkanes and alkenes, particularly trichloroethylene before 1974. There were no similar findings on other types of cancer.

CONCLUSION

Female workers with exposure to trichloroethylene and/or mixture of solvents, first employed prior to 1974, may have an excess risk of breast cancer.

Factors affecting decreasing radiation dose for mammography in North Carolina after 2002: an analysis of Food and Drug Administration annual surveys

RATIONALE AND OBJECTIVES

We sought to determine which factors affected the decrease in average glandular dose recorded at the annual U.S. Food and Drug Administration Mammography Quality Standards Act inspections of mammography equipment in North Carolina from 2002 through 2005.

MATERIALS AND METHODS

Average glandular dose, half-value layer, kVp, equipment age, processing speed, and system speed for every mammography unit in the state were collected by Food and Drug Administration-trained state inspectors. A mixed-effect model was used to evaluate the changes of glandular dose over time and to identify the factors associated with these changes.

RESULTS

There was a statistically significant decrease in average glandular dose in North Carolina since 2002. Factors that were statistically significantly associated with this effect were changes in kVp, equipment age, processing speed, and system speed.

CONCLUSION

Average glandular dose for mammography has decreased in North Carolina after 2002. This change is probably at least partially due to the cumulative effect of direct intervention by mammography consultants and statewide educational seminars on mammography quality control.

Radiation injury is a potentially serious complication to fluoroscopically-guided complex interventions

Radiation-induced injury to skin is an infrequent but potentially serious complication to complex fluoroscopically-guided interventional procedures. Due to a lack of experience with such injuries, the medical community has found fluoroscopically-induced injuries difficult to diagnose. Injuries have occurred globally in many countries. Serious injuries most frequently occur on the back but have also occurred on the neck, buttocks and anterior of the chest. Severities of injuries range from skin rashes and epilation to necrosis of the skin and its underlying structures. This article reviews the characteristics of these injuries and some actions that can be taken to reduce their likelihood or seriousness.

Risk of breast cancer in female survivors of childhood Hodgkin's disease in Britain: a population-based study

There is now widespread evidence that female survivors of Hodgkin's disease who have been treated with supradiaphragmatic radiotherapy are at an increased risk of breast cancer. Mantle irradiation, which includes irradiation of the mediastinum, conveys a particularly high risk. Previously published studies have found a wide variation in risk. To provide British estimates of risk to inform surveillance programmes, we carried out the first British population-based cohort study of breast cancer in female survivors of childhood Hodgkin's disease. From the underlying cohort of the British Childhood Cancer Survivor Study, a cohort of 18,123 British 5-year survivors of childhood cancer diagnosed between 1940 and 1991, there were in total 383 female 5-year survivors of childhood Hodgkin's disease. Sixteen of these 383 survivors went on to develop invasive breast cancer subsequent to 5-year survival (standardised incidence ratio, 11.5; 95% confidence interval (95% CI), 6.6-18.6) and all of these 16 survivors had been treated with supradiaphragmatic irradiation as treatment for childhood Hodgkin's disease. The cumulative risk of breast cancer by 25 years of follow up was 9.9% (95% CI, 3.3-16.6) for all patients and 12.2% (95% CI, 4.3-20.1) for those treated with supradiaphragmatic radiotherapy. The cumulative risk of breast cancer in female survivors of childhood Hodgkin's disease in Britain is at the lower end of previous estimates. We hope that our data may provide a basis for future surveillance and for counselling survivors as to their likely risk of breast cancer.

Coronary calcium scoring with MDCT: The radiation dose to the breast and the effectiveness of bismuth breast shield

OBJECTIVE

The purpose of our study was to determine the breast radiation dose during coronary calcium scoring with multidetector computerized tomography (MDCT). We also evaluated the degree of dose reduction by using a bismuth breast shield when performing coronary calcium scoring with MDCT.

MATERIALS AND METHODS

The dose reduction achievable by shielding the adult (35 years or older) female breasts was studied in 25 women who underwent coronary calcium scoring with MDCT. All examinations were performed with a 16-MDCT scanner. To compare the shielded versus unshielded breast dose, the examinations were performed with (right breast) and without (left breast) breast shielding in all patients. With this technique the superficial breast doses were calculated. To determine the average glandular breast radiation dose, we imaged an anthropomorphic dosimetric phantom into which calibrated dosimeters were placed to measure the dose to the breast. The phantom was imaged using the same protocol. Radiation doses to the breasts with and without the breast shielding were measured and compared using the Student's t-test.

RESULTS

The mean radiation doses with and without the breast shield were 5.71+/-1.1 mGy versus 9.08+/-1.5 mGy, respectively. The breast shield provided a 37.12% decrease in radiation dose to the breast with shielding. The difference between the dose received by the breasts with and without bismuth shielding was significant, with a p-value of less than 0.001.

CONCLUSION

The high radiation during MDCT greatly exceeds the recommended doses and should not be underestimated. Bismuth in plane shielding for coronary calcium scoring with MDCT decreased the radiation dose to the breast. We recommend routine use of breast shields in female patients undergoing calcium scoring with MDCT.

Female Breast Radiation Exposure During Thorax Multidetector Computed Tomography and the Effectiveness of Bismuth Breast Shield to Reduce Breast Radiation Dose

OBJECTIVE

The purpose of our study was to determine the breast radiation dose when performing routine thoracic multidetector computed tomography (MDCT). We also evaluated dose reduction and the effect on image quality of using a bismuth breast shield when performing thoracic MDCT.

MATERIAL AND METHODS

The dose reduction achievable by shielding the adult (18 years or older) female breasts was studied in 50 women who underwent routine thoracic MDCT. All examinations were performed with a 16-MDCT scanner (Sensation Cardiac 16; Siemens Medical Solutions). To compare the shielded/unshielded breast dose, the examination was performed with (right breast) and without (left breast) breast shielding in all patients. With this technique, the superficial breast doses were calculated. To determine the average glandular breast radiation dose, we imaged an anthropomorphic dosimetric phantom into which calibrated dosimeters were placed to measure the dose to breast. The phantom was imaged using the same protocol. Radiation doses to the breasts with and without the breast shielding were measured and compared using the Student t test.

RESULTS

In the qualitative evaluation of the MDCT scans, all were considered to be of diagnostic quality. We did not see any differences in quality between the shielded and unshielded lung. The mean radiation doses to the breasts with the shield and to those without the shield were 8.6 +/- 2.33 versus 14.46 +/- 3.94 mGy, respectively. The breast shield enabled a 40.53% decrease in radiation dose to the breast. The difference between the dose received by the breasts with and that received by the breasts without bismuth shielding was significant, with a P value of less than 0.001.

CONCLUSIONS

Bismuth in-plane shielding for routine thoracic MDCT decreased radiation dose to the breast without qualitative changes in image quality. The other radiosensitive superficial organs (eg, testes and thyroid gland) specifically must be protected with shielding.

Factors affecting increasing radiation dose for mammography in North Carolina from 1997 through 2001: an analysis of Food and Drug Administration annual surveys

RATIONALE AND OBJECTIVES

To determine which factors affected the increase in average glandular dose recorded at the annual US Food and Drug Administration Mammography Quality Standards Act inspections of mammography equipment in North Carolina from 1997 to 2001.

MATERIALS AND METHODS

Average glandular dose, HVL, kVp, ambient light, luminance, equipment age, processing speed, and system speed for every mammography unit at all facilities in the state were collected by state inspectors. A mixed-effect model was used to assess the average changes of glandular dose over time and to identify the factors associated with these changes.

RESULTS

There was a statistically significant increase in the average glandular dose in North Carolina in 1999, 2000, and 2001 when compared with the baseline year of 1997. Factors that were statistically significantly linked to this effect were changes in kVp, processing speed, and system speed.

CONCLUSION

Average glandular dose for mammography has recently increased in North Carolina. This change is likely caused by changes in screen-film products and processing techniques.

Long-term follow-up of the residents of the Three Mile Island accident area: 1979-1998

The Three Mile Island (TMI) nuclear power plant accident (1979) prompted the Pennsylvania Department of Health to initiate a cohort mortality study in the TMI accident area. This study is significant because of the long follow-up (1979-1998), large cohort size (32,135), and evidence from earlier reports indicating increased cancer risks. Standardized mortality ratios (SMRs) were calculated to assess the mortality experience of the cohort compared with a local population. Relative risk (RR) regression modeling was performed to assess cause-specific mortality associated with radiation-related exposure variables after adjustment for individual smoking and lifestyle factors. Overall cancer mortality in this cohort was similar to the local population [SMRs = 103.7 (male); 99.8 (female)]. RR modeling showed neither maximum gamma nor likely gamma exposure was a significant predictor of all malignant neoplasms; bronchus, trachea, and lung; or heart disease mortality after adjusting for known confounders. The RR estimates for maximum gamma exposure (less than or equal to 8, 8-19, 20-34, greater than or equal to 35 mrem) in relation to all lymphatic and hematopoietic tissue (LHT) are significantly elevated (RRs = 1.00, 1.16, 2.54, 2.45, respectively) for males and are suggestive of a potential dose-response relationship, although the test for trend was not significant. An upward trend of RRs and SMRs for levels of maximum gamma exposure in relation to breast cancer in females (RRs = 1.00, 1.08, 1.13, 1.31; SMRs = 104.2, 113.2, 117.9) was also noted. Although the surveillance within the TMI cohort provides no consistent evidence that radioactivity released during the nuclear accident has had a significant impact on the overall mortality experience of these residents, several elevations persist, and certain potential dose-response relationships cannot be definitively excluded.

Pure Squamous Cell Carcinoma of the Breast in a Patient with Previous Adenocarcinoma of the Breast: A Case Report and Review of the Literature

We report a case of squamous cell carcinoma of the breast in a patient with previous adenocarcinoma in the unilateral breast. Squamous cell carcinoma is often cystic in nature with a variable presentation on mammogram. Its diagnosis necessitates the preclusion of a primary site of squamous carcinoma elsewhere in the body. The treatment of this cancer is similar to other types of breast carcinoma. Its prognosis remains unclear.

Radiation and breast carcinogenesis

With the possible exception of radiation-induced leukemia, more is known about radiation-induced breast cancer than any other malignancy. Fourteen cohort studies have provided quantitative information on the level of risk following a wide range of doses in different populations around the world. Comprehensive studies have been conducted in Canada, Germany, Japan, Sweden and other Nordic countries, the United Kingdom, and the USA [Table I in text]. Key features are the linearity in the dose response (i.e., a straight line adequately fits the observed data), and the effect modification of age at exposure (i.e., risk is inversely related to exposure age and exposures past the menopausal ages appear to carry a very low risk); and the minimal effect of fractionating dose on subsequent risk. A recent combined analysis of almost 78,000 women and 1,500 breast cancer cases from eight cohorts confirmed the downturn in risk at the highest dose levels (related in part to the killing of cells rather than transformation) and that fractionation of dose has little influence on risk, at least on an absolute scale. It is not known whether persons predisposed to cancer are at enhanced risk of radiation-induced breast cancer from low-dose exposures, although this seems unlikely. New data on the effects of high doses following childhood exposures will be forthcoming from long-term studies of the survivors of childhood cancer.

Carcinoma of the male breast

Male breast cancer accounts for less than 1% of all breast cancers in the United States. The low incidence of this disease prevents therapeutic questions from being addressed in prospective randomized trials. As such, treatment algorithms have generally been extrapolated from those used in female breast cancer. Similar to female breast cancer, lymph node involvement and the size of the primary tumor are the most important factors in predicting disease-free and overall survival. Modified radical mastectomy remains the standard local therapeutic approach, with radiation therapy indicated for patients who have clinicopathologic features associated with a high risk for postmastectomy chest wall or lymph node recurrence. Similar to female breast cancer, adjuvant chemotherapy or hormonal therapy is indicated in the majority of men with breast cancer, specifically those with tumors larger than 1 cm or those with lymph node-positive disease.

Mortality among the residents of the Three Mile Island accident area: 1979-1992

The largest U.S. population exposed to low-level radioactivity released by an accident at a nuclear power plant is composed of residents near the Three Mile Island (TMI) Plant on 28 March 1979. This paper (a collaboration of The University of Pittsburgh and the Pennsylvania Department of Health) reports on the mortality experience of the 32,135 members in this cohort for 1979-1992. We analyzed standardized mortality ratios (SMRs) using a local comparison population and performed relative risk regression modeling to assess overall mortality and specific cancer risks by confounding factors and radiation-related exposure variables. Total mortality was significantly elevated for both men and women (SMRs = 109 and 118, respectively). All heart disease accounted for 43.3% of total deaths and demonstrated elevated SMRs for heart disease of 113 and 130 for men and women, respectively; however, when controlling for confounders and natural background radiation, these elevations in heart disease were no longer evident. Overall cancer mortality was similar in this cohort as compared to the local population (male SMR = 100; female SMR = 101). In the relative risk modeling, there was a significant effect for all lymphatic and hematopoietic tissue in males in relation to natural background exposure (p = 0.04). However, no trend was noted. We found a significant linear trend for female breast cancer risk in relation to increasing levels of TMI-related likely [gamma]-exposure (p = 0.02). Although such a relationship has been noted in other investigations, emissions from the TMI incident were significantly lower than in other documented studies. Therefore, it is unlikely that this observed increase is related to radiation exposure on the day of the accident. The mortality surveillance of this cohort does not provide consistent evidence that radioactivity released during the TMI accident has a significant impact on the mortality experience of this cohort to date. However, continued follow-up of these individuals will provide a more comprehensive description of the morbidity and mortality experience of the cohort.

Real-time portal monitoring to estimate dose to skin of patients from high dose fluoroscopy

Since doses to skin of patients from fluoroscopically-guided interventional procedures can be very high, real-time monitoring of skin dose is important for both patient management and quality control. The use of a scintillation detector, placed on the X-ray port to measure potential skin dose, was investigated, focusing on the uncertainties related to the technique. Sources of uncertainty include performance characteristics of the dosemeter, errors in calibration, patient set-up and changes during the procedure. Some of the largest sources of error include uncertainty in source-to-skin distance, heel effect, difficulty in identifying the area of skin principally exposed, calibration error, energy dependence of the dosemeter and the dose rate dependence of the monitor. This technique is found to be beneficial for radiation management, but users must be cognizant of the potential errors of the method and the limitations that these place on quality control and patient management. Knowing the limitations and minimizing the sources of error enhance the utility of the technique.

Incidence of breast carcinoma in women with thyroid carcinoma

BACKGROUND

Breast carcinoma and differentiated thyroid carcinoma(the most common endocrine malignancy) occur predominantly in women. An association between the two tumors has been suggested by some investigators, but the potential impact of treatment of one of these diseases on the development of the other remains unclear. The authors examined the relation between the occurrence of these two tumors.

METHODS

There were 41,686 patients with breast carcinoma and 3662 with thyroid carcinoma who registered at The University of Texas M. D. Anderson Cancer Center between March 1944 and April 1997. Women who received both diagnoses since 1976 were identified and incidence rates and relative risks of secondary tumor development were calculated. Surveillance, Epidemiology and End Results (SEER) program data on the age-adjusted incidences of these diseases during the same time period were used for the expected incidences in the same population.

RESULTS

Among 18,931 women with a diagnosis of breast carcinoma since 1976, 11 developed differentiated thyroid carcinoma > or = 2 years after the diagnosis of breast carcinoma. These breast carcinoma patients contributed 129,336 person-years of follow-up; the observed incidence of thyroid carcinoma in this group was not different from that in a similar age group of women in the SEER database. Among 1013 women with a diagnosis of thyroid carcinoma since 1976, 24 developed breast carcinoma > or = 2 years after the diagnosis of thyroid carcinoma. These thyroid carcinoma patients contributed 8380 person-years of follow-up; the observed incidence of breast carcinoma in women ages 40-49 years was significantly higher than the expected incidence for women in the same age group in the SEER database.

CONCLUSIONS

Breast carcinoma developing after thyroid carcinoma was diagnosed more frequently than expected in young adult women seen at the study institution since 1976. This potential association and plausible mechanisms of breast carcinoma development after thyroid carcinoma should be evaluated in larger cohorts of patients.

High risk of breast carcinoma after irradiation of young women with Hodgkin's disease

BACKGROUND

Treatment-associated second neoplasms have emerged as a major threat to the continued survival of patients cured of Hodgkin's disease. In this study, the authors investigated the risk of breast carcinoma in an irradiated Hodgkin's disease population.

METHODS

One hundred and eleven women younger than 60 years presenting between 1964 and 1984 with Stage I and II Hodgkin's disease who received mantle irradiation were retrospectively analyzed and compared with an age specific population. Median follow-up was 18 years (range, 10-30 years), and the median age at initiation of therapy was 24 years. Kaplan-Meier actuarial risks, relative risks (RRs) (the ratio of the observed to the expected cases) with 95% confidence intervals (CIs), and the log rank test for trends were calculated.

RESULTS

Fourteen women developed breast carcinoma: 8 of 33 patients younger than 20 years at the time of irradiation, 5 of 48 patients age 20 to 29 years, and 1 of 30 patients age 30 years or older. Actuarial calculation predicted a 34.0% (CI, 14.2-53.8) risk of breast carcinoma at 25 years after therapy for the youngest group, 22.3% (CI, 4.1-40.5) for the group of intermediate age, and 3.5% (CI, 0-10.1) for the oldest group. The RR of breast carcinoma was 56 (CI, 23.3-107) for those 19 years or younger at the time of treatment, 7.0 (CI, 2.3-16.4) for those age 20-29 years, and 0.9 (CI, 0-5.3) for those 30 years and older. Excluding 1 patient who was age 38 years at the time of irradiation, the remaining 13 breast carcinomas were tightly clustered in women irradiated between the ages of 14 through 25, and were detected in years 11 through 25 after treatment, with 7 occurring in years 15 through 18.

CONCLUSIONS

Women younger than 30 years, particularly those younger than 20 years, who have received mantle irradiation for Hodgkin's disease require meticulous follow-up for breast carcinoma. The high incidence of breast carcinoma in this patient population should be considered when making treatment decisions in young women with early stage Hodgkin's disease.

Breast cancer and other second neoplasms after childhood Hodgkin's disease

BACKGROUND

Patients who survive Hodgkin's disease are at increased risk for second neoplasms. As survival times increase, solid tumors are emerging as a serious long-term complication.

METHODS

The Late Effects Study Group followed a cohort of 1380 children with Hodgkin's disease to determine the incidence of second neoplasms and the risk factors associated with them.

RESULTS

In this cohort, there were 88 second neoplasms as compared with 4.4 expected in the general population (standardized incidence ratio, 18.1; 95 percent confidence interval, 14.3 to 22.3). The estimated actuarial incidence of any second neoplasm 15 years after the diagnosis of Hodgkin's disease was 7.0 percent (95 percent confidence interval, 5.2 to 8.8 percent); the incidence of solid tumors was 3.9 percent (95 percent confidence interval, 2.3 to 5.5 percent). Breast cancer was the most common solid tumor (standardized incidence ratio 75.3; 95 percent confidence interval, 44.9 to 118.4), with an estimated actuarial incidence in women that approached 35 percent (95 percent confidence interval, 17.4 to 52.6 percent) by 40 years of age. Older age (10 to 16 vs. <10 years) at the time of radiation treatment (relative risk, 1.9) and a higher dose (2000 to 4000 vs. <2000 cGy) of radiation (relative risk, 5.9) were associated with significantly increased risk of breast cancer. The estimated actuarial incidence of leukemia reached a plateau of 2.8 percent (95 percent confidence interval, 0.8 to 4.8 percent) 14 years after diagnosis. Treatment with alkylating agents, older age at the diagnosis of Hodgkin's disease, recurrence of Hodgkin's disease, and a late stage of disease at diagnosis were risk factors for leukemia.

CONCLUSIONS

The risk of solid tumors, especially breast cancer, is high among women who were treated with radiation for childhood Hodgkin's disease. Systematic screening for breast cancer could be important in the health care of such women.

Recent developments in breast imaging

A review of breast imaging has already appeared in 1982 in this journal. Consequently, the present article concentrates on a discussion of only those developments of a more recent nature. Although the emphasis is placed on the physical aspects of the different imaging methods concerned, the essential factors relating to the clinical background and the associated radiation risk are also outlined. The completeness of detail depends on the present clinical importance of the method under discussion. X-ray mammography, which is still the most important breast imaging technique and has proved to be an effective method for breast cancer screening, is therefore treated in greater detail. Since the early 1980s, ultrasound B-mode scanning has evolved to an indispensable adjunct to x-ray mammography. For Doppler sonography, diaphanography, contrast-enhanced MRI, CT and DSA, the visualization of a tumour depends essentially on the enhanced vascularity of the lesion. Whether this will prove to be a reliable indicator for malignancy remains to be shown in controlled clinical studies. Common to all imaging systems is the increasing use of digital methods for signal processing, which also offers the possibility of computer-aided diagnosis by texture analysis and pattern recognition.

Manipulation under anaesthetic of children's fractures: use of the image intensifier reduces radiation exposure to patients and theatre personnel

During simulated manipulation of children's forearm fractures, levels of scattered radiation from both plain radiographs and an image intensifier in different modes were measured at various sites on the surgeon, anaesthetist, radiographer, and patient both with and without recommended shielding. By using fluoroscopy in the pulsed screening mode but allowing only single pulses to occur, radiation levels could be substantially reduced to the eye, thyroid, and gonads of all those exposed. The radiographer and the anaesthetist were so far from the source and guarded by various pieces of equipment that levels were almost unrecordable. Effective dose equivalent for the surgeon using pulsed mode, based on circa six pulses per manipulation, during 100 manipulations per year, would equate to 1 microSv even in the unshielded state (< 0.1 microSv shielded), which is approximately 1/1,000 of background radiation at sea level. Because the current dose limit is 50 mSv (50,000 microSv) per year for employees, we are many orders of magnitude in the safety zone.

Breast cancer

This synthesis of the literature on radiotherapy for breast cancer is based on 97 scientific articles, including 5 meta-analyses, 38 randomized studies, and 27 retrospective studies. These studies involve 387634 patients. Radiotherapy is the most effective method for preventing locoregional recurrence following primary surgery for invasive breast cancer, and radiotherapy is currently more effective than adjuvant chemotherapy after either mastectomy or breast-conserving surgery. Radiotherapy in patients at high risk for locoregional recurrence, eg, patients with spread to the axillary lymph nodes, leads to a significant increase in relapse free survival (eg, 1, 3). Meta-analyses have shown that radiotherapy in these subgroups of patients can reduce the risk for distant metastasis and reduce the risk for cancer death. These analyses have not statistically confirmed an improvement in total survival, probably because reduced mortality from breast cancer has been offset by increased mortality from cardiovascular disease. However, the results have successively improved, and survival gains are significantly greater in recent studies using modern treatment methods. It is probable that survival gains from radiotherapy do not exceed those that can be achieved by other adjuvant treatment of breast cancer such as chemotherapy or hormones, ie, a reduction in mortality by 20% to 30%, leading to an increased total survival after, eg, 10 years of 5% to 10%. The heart is the most important organ at risk during radiotherapy for breast cancer. Minimizing radiation doses to the heart muscle and the coronary arteries is necessary for avoiding later effects of ischemic cardiovascular disease. These side effects were particularly prominent in early treatment studies that used older radiotherapy methods. Radiotherapy in conjunction with breast-conserving surgery for invasive breast cancer significantly reduces the recurrence frequency in the breast. Clinical studies are under way that aim at further defining the role of radiotherapy as an element in a breast-conserving treatment strategy, e.g., determining the value of boost, and identifying prognostic/predictive factors for breast recurrence. Improved knowledge about such factors should eventually permit identification of patient groups at such low risk for breast recurrence that routine radiotherapy is unnecessary, or at such high risk-even with radiotherapy-that alternatives to breast conserving surgery should be considered. Radiotherapy also reduces the risk for recurrence in the breast following breast-conserving surgery of DCIS. Controlled trials are under way that aim at more closely defining the roles of surgical methods and radiotherapy for various subgroups of patients, eg, regarding different histopathologic types of DCIS. Radiotherapy has a substantial palliative value to patients who cannot be cured. It can reduce, prevent, or delay unpleasant symptoms from advanced disease, eg, pain, cancer lesions, fractures, neurologic symptoms. etc.

Timing of weight gain in relation to breast cancer risk

Excessive weight gain in women at the time of intense hormonal change can result in metabolic dysfunction. The metabolic/endocrine effect of puberty, pregnancy or menopause on breast tissue 'aging' is likely to be more relevant to a woman's breast cancer risk than is her degree of obesity at the time when the cancer presents. Experimental evidence suggests that the susceptibility of mammary tissue to carcinogenesis is greatest in early adult life, and multiple studies show that a history of weight gain in early adult life is associated with increased breast cancer risk in Western women. Excessive weight gain in that age group is associated with the development of hyperinsulinaemia in individuals with genetic susceptibility to insulin resistance. The insulin resistance syndrome may be a metabolic link between weight gain and breast cancer risk in Western women. Some studies suggest that in postmenopausal women, hyperinsulinaemia is related more to overall obesity, whereas in premenopausal women it is related more to abdominal localisation of fat. This may explain why an increased body mass index is a risk marker for breast cancer in postmenopausal but not premenopausal women. (A premenopausal woman with an average body mass index may have a large intra-abdominal fat mass associated with the presence of hyperinsulinaemia.) It is hypothesised that over-nutrition and inadequate physical exercise favour the development of hyperinsulinaemia and also increase breast cancer risk in women with a genetic susceptibility to both conditions. The hypothesis can be tested by specific intervention studies.