Frequent chest X-ray fluoroscopy and breast cancer incidence among tuberculosis patients in Massachusetts

The incidence of breast cancer was determined in 4940 women treated for tuberculosis between 1925 and 1954 in Massachusetts. Among 2573 women examined by X-ray fluoroscopy an average of 88 times during lung collapse therapy and followed for an average of 30 years, 147 breast cancers occurred in contrast to 113.6 expected [observed/expected (O/E) = 1.29; 95% confidence interval (CI) = 1.1-1.5]. No excess of breast cancer was seen among 2367 women treated by other means: 87 observed versus 100.9 expected. Increased rates for breast cancer were not apparent until about 10 to 15 years after the initial fluoroscopy examination. Excess risk then remained high throughout all intervals of follow-up, up to 50 years after first exposure. Age at exposure strongly influenced the risk of radiation-induced breast cancer with young women being at highest risk and those over age 40 being at lowest risk [relative risk (RR) = 1.06]. Mean radiation dose to the breast was estimated to be 79 cGy, and there was strong evidence for a linear relationship between dose and breast cancer risk. Allowing for a 10-year minimum latent period, the relative risk at 1 Gy was estimated as 1.61 and the absolute excess as 10.7 per 10(4) woman-years per gray. When compared to other studies, our data suggest that the breast is one of the most sensitive tissues to the carcinogenic force of radiation, that fractionated exposures are similar to single exposures of the same total dose in their ability to induce breast cancer, that risk remains high for many years after exposure, and that young women are especially vulnerable to radiation injury.     

Breast cancer following multiple chest fluoroscopy: the Ontario experience

The hypothesis, derived from experience in Nova Scotia, that artificial pneumothorax, requiring repeated fluoroscopy of the chest, is associated with an increased risk of subsequent breast cancer was tested in Ontario by means of a retrospective cancer patient/control study using record linkage. Sanatorium patients treated by artificial pneumothorax were estimated to have incurred a risk of breast cancer between two and three times as high as that of matched, contemporary sanatorium patients treated by other means. There was a tendency for the malignant disease to develop on the side of collapse, and there was evidence of a characteristic latent interval between exposure and onset.     

Tuberculosis in female nurses in British Columbia: implications for control programs.

All 57 cases of active tuberculosis in women in nursing and related assisting occupations (henceforth called nurses) notified in British Columbia between 1969 and 1979 were reviewed. This represented a mean annual incidence of active tuberculosis of 2.6/10 000, similar to that in other women, adjusted for age and birthplace. The rate varied according to birthplace: among nurses born in Canada the rate was 2.0, almost twice that of other women born in Canada, and among those born in Asia it was 24.8, less than half that of other women born in Asia. The nurses born in Canada who had received BCG (bacille Calmette-Guérin) during their training were least likely to contract tuberculosis, the incidence rate being comparable to that among other women. Those whose results of tuberculin testing were negative but who were not vaccinated were twice as likely to contract tuberculosis, whereas those whose results were positive at the start of training were four times as likely to contract tuberculosis. The feasibility and implications of a tuberculosis screening and surveillance program are discussed.     

Animal carcinogenicity studies: implications for the REACH system

The 2001 European Commission proposal for the Registration, Evaluation and Authorisation of Chemicals (REACH) aims to improve public and environmental health by assessing the toxicity of, and restricting exposure to, potentially toxic chemicals. The greatest benefits are expected to accrue from decreased cancer incidences. Hence the accurate identification of chemical carcinogens must be a top priority for the REACH system. Due to a paucity of human clinical data, the identification of potential human carcinogens has conventionally relied on animal tests. However, our survey of the US Environmental Protection Agency's (EPAs) toxic chemicals database revealed that, for a majority of the chemicals of greatest public health concern (93/160, i.e. 58.1%), the EPA found animal carcinogenicity data to be inadequate to support classifications of probable human carcinogen or non-carcinogen. A wide variety of species were used, with rodents predominating; a wide variety of routes of administration were used; and a particularly wide variety of organ systems were affected. These factors raise serious biological obstacles that render accurate extrapolation to humans profoundly difficult. Furthermore, significantly different International Agency for Research on Cancer assessments of identical chemicals, indicate that the true human predictivity of animal carcinogenicity data is even poorer than is indicated by the EPA figures alone. Consequently, we propose the replacement of animal carcinogenicity bioassays with a tiered combination of non-animal assays, which can be expected to yield a weight-of-evidence characterisation of carcinogenic risk with superior human predictivity. Additional advantages include substantial savings of financial, human and animal resources, and potentially greater insights into mechanisms of carcinogenicity.     

FPs have vital role in ensuring success of breast cancer screening programs

SCREENING IS THE ONLY PROVEN STRATEGY for reducing breast cancer mortality in women older than 50. Over the last 9 years, 8 provinces and 2 (territories have established independent dedicated mammography programs. A recent workshop on screening programs was told that family physicians play a crucial role in the ultimate success of these programs because of their referral role.     

Estimated benefits and risks of screening for breast cancer.

A controlled randomized trial of breast cancer screening has been initiated in Canada. This paper presents an analysis of the possible benefit from screening relative to the possible radiation risk from mammography for those women who will be screened in the trial. It shows that with modern low-dose mammography, even when a conservative estimate of possible reduction in mortality due to early detection is applied to the data, the estimated benefit substantially exceeds any possible hazard.     

Mammographic screening and mortality from breast cancer: the Malm? mammographic screening trial.

STUDY OBJECTIVE--To determine whether mortality from breast cancer could be reduced by repeated mammographic screening. DESIGN--Birth year cohorts of city population separately randomised into study and control groups. SETTING--Screening clinic outside main hospital. PATIENTS--Women aged over 45; 21,088 invited for screening and 21,195 in control group. INTERVENTIONS--Women in the study group were invited to attend for mammographic screening at intervals of 18-24 months. Five rounds of screening were completed. Breast cancer was treated according to stage at diagnosis. END POINT--Mortality from breast cancer. MEASUREMENTS AND MAIN RESULTS--All women were followed up and classed at end point as alive without breast cancer, alive with breast cancer, dead from breast cancer, or dead from other causes. Cause of death was taken from national mortality registry and for patients with breast cancer was validated independently. Mean follow up was 8.8 years. Altogether 588 cases of breast cancer were diagnosed in the study group and 447 in the control group; 99 v 94 women died of all causes and 63 v 66 women died of breast cancer (no significant difference; relative risk 0.96 (95% confidence interval 0.68 to 1.35)). In the study group 29% more women aged less than 55 died of breast cancer (28 v 22; relative risk 1.29 (0.74 to 2.25)). More women in the study group died from breast cancer in the first seven years; after that the trend reversed, especially in women aged greater than or equal to 55 at entry. Overall, women in the study group aged greater than or equal to 55 had a 20% reduction in mortality from breast cancer (35 v 44; relative risk 0.79 (0.51 to 1.24)). OTHER FINDINGS--In the study group 100 (17%) cancers appeared in intervals between screenings and 107 (18%) in non-attenders; 51 of these women died from breast cancer. Cancers classed as stages II-IV comprised 33% (190/579) of cancers in the study group and 52% (231/443) in the control group. CONCLUSIONS--Invitation to mammographic screening may lead to reduced mortality from breast cancer, at least in women aged 55 or over.     

Cervical cancer screening programs: summary of the 1982. Canadian task force report.

The Canadian Task Force on Cervical Cancer Screening Programs, which produced its first report in 1976, was reconvened by the Department of National Health and Welfare in 1980 in response to concerns expressed about the significance of new data, changing sociosexual patterns and wide variations in the implementation of the 1976 recommendations. This article is a summary of the 1982 task force report. In addition to updates of the 1976 material new sections appear on groups at risk, mathematical models of screening, quality control in screening programs, cytologic screening coverage of the Canadian population and management of patients with abnormal smears. The 1982 recommendations deal with frequency of screening, laboratory quality control and follow-up mechanisms. The task force concludes that measures to improve the quality and sensitivity of screening programs and to include women who have never been screened will be more effective in reducing mortality from carcinoma of the cervix than will attempts to increase the frequency of screening. The task force views as unnecessary the annual screening of women over 35 years of age whose previous smears have been normal. Since younger women are sexually more active and tend to have more than one sexual partner they are at high risk. Therefore, the task force recommends annual screening for sexually active women aged 18 to 35 years. Physicians, health care professionals and government health agencies have a role to play in informing women about the recommended intervals for cervical smears and ensuring that screening programs of adequate quality are available. Although women are primarily responsible for entering and continuing in such a program, government-sponsored registries are essential if the full potential of cervical smear programs is to be realized.