Differences In Breast Cancer Mortality Research Articles

La epidemia de cáncer de mama en México: ¿Consecuencia de la transición demográfica?

Objective. Analyze the relation between reductions in fertility and the inverse en breast cancer mortality in the differents states of Mexico for the period 1979-1994. Materials and methods. Fertility rates and beast cancer mortality rates were utilized to analyze the proposed relationship in the states of the country. Principal component analysis and classification analysis were then used in the confirmatory analysis of this relationship. Results. There is an important decrease in fertility trends overall with regional differences: the northern states of Mexico have lowest then the southern states. These regional differences are inversetly related to the observed differences in breast cancer mortality within the states: the northern states have levels of breast cancer mortality much higher than the southern states. Conclusions. The increase in mortality due to breast cancer and its relation to the decrease in fertility illustrates the importance that must be given to the preventive aspect of health services since in the near future Mexican women will exhibit reproductive behaviors similar to women in developed countries.

Breast cancer mortality after 10 years in the UK Trial of Early Detection of Breast Cancer

The United Kingdom Trial of Early Detection of Breast Cancer is a population-based but non-randomized controlled trial of the effect on breast cancer mortality of two early detection strategies: a) screening in which mammography was provided at 24 month intervals in addition to annual physical (clinical) examination for a period of 7 years and b) education in breast self-examination (BSE). Women aged 45–64 at entry in two screening districts, two BSE districts and four comparison districts have been followed up for 10 years through flagging their records at the National Health Service Central Registries. The reduction in breast cancer mortality observed after 7 years in the screening districts has been sustained. The risk in the combined screening populations relative to the comparison populations is 0.80 (95% CI 0.67–0.95) after adjustment for pre-trial breast cancer mortality. No reduction is seen in the BSE centres when viewed together but there is a considerable and unexpected difference between the two. Analysis by age at entry suggests that women aged 45–49 at entry experienced a similar benefit to older women though the power of the study to detect age-specific differences is weak. It was not possible to adjust for all the factors other than the early detection interventions which may have contributed to differences in breast cancer mortality. The non-randomized design of the study has thus proved to be a serious impediment to interpretation of the results but the study continues to provide support for the view that screening can reduce breast cancer mortality by about 20% in the age-group now targeted by the UK national screening programme. Any benefit of teaching BSE remains unproven.

Geographic variation in breast cancer mortality in the United States: A hypothesis involving exposure to solar radiation

Epidemiologic and laboratory evidence suggests that vitamin D may play a role in reducing breast cancer risk. Lack of exposure to ultraviolet sunlight can increase the prevalence of vitamin D deficiency. This deficiency may place some populations at higher risk for breast cancer. The association between total average annual sunlight energy striking the ground and age-adjusted breast cancer mortality rates in 87 regions of the United States was evaluated. Annual age-adjusted mortality rates for breast cancer varied over a 1.8-fold range, from 17–19 per 100,000 in the South and Southwest United States to 33 per 100,000 in the Northeast; the overall U.S. rate was 27.3 per 100,000. Risk of fatal breast cancer in the major urban areas of the United States was inversely proportional to intensity of local sunlight ( r = −0.80, P = 0.0001; multiple regression with stratospheric ozone measurements, r = −0.82, P = 0.0001). Vitamin D from sunlight exposure may be associated with low risk for fatal breast cancer, and differences in ultraviolet light reaching the United States population may account for the striking regional differences in breast cancer mortality. The ecological nature of this study is emphasized, and the possibility that an indirect association with dietary and socioeconomic factors could explain these findings is discussed.

FIRST RESULTS ON MORTALITY REDUCTION IN THE UK TRIAL OF EARLY DETECTION OF BREAST CANCER

Between 1979 and 1981 the UK Trial of Early Detection of Breast Cancer enrolled women aged 45-64 living in eight locations in the United Kingdom. Annual screening by clinical examination of the breast, with mammography in alternate years, was provided over 7 years for 45 841 women; 63 636 were offered teaching in breast self-examination and were provided with a self-referral clinic; and 127 117, for whom no extra services were provided, form a comparison population. Over the 7 years from the start of the trial a reduction in the risk of dying from breast cancer in women offered screening relative to that in the comparison population was observed. The reduction was 14% (RR 0·86, 95% CI 0·69-1·08) when no allowance was made for underlying differences in breast cancer mortality between the populations, but rose to 20% (RR 0·80, 95% CI 0·64-1·01) when adjusted for differences in pretrial mortality rates. These differences fall short of statistical significance. No reduction in mortality was observed during the first 5 years but thereafter the gap widens. These results, though in themselves inconclusive, are consistent with the hypothesis that screening can achieve a worthwhile mortality reduction. No difference in mortality has so far been observed between women offered teaching in breast self-examination and the comparison population