Global Progress: Breast Cancer Mortality

The long-term, worldwide trend of rising breast cancer mortality has apparently been reversed in several countries, with significant declines reported in the 1990s in the United States, United Kingdom, and Canada. These are the findings of a study conducted at Roswell Park Cancer Institute by Curtis J. Mettlin, PhD, Department of Cancer Prevention, Epidemiology and Biostatistics, and published in the May/June 1999 issue of CA—A Cancer Journal for Physicians.

Dr. Mettlin drew his conclusion following a statistical analysis of breast cancer mortality in 41 countries reporting 1,000 or more breast cancer deaths annually, as tabulated in the World Health Organization Cancer Mortality Databank.

The overall pattern for breast cancer mortality was found to be high for western, industrialized nations, particularly those in northern Europe and North America, and lower for less industrialized and Asian countries. “These differences may be attributable to factors that are thought to be important in breast cancer etiology such as nulliparity and later age at first live birth, diets high in polyunsaturated fat and other environmental factors,” said Dr. Mettlin.

Possible Causes of Mortality Decline

The decline in breast cancer mortality observed in many countries, including the United States, United Kingdom, Canada, Austria, and Sweden, may be due to earlier diagnosis from increased mammographic screening and improved survival from increased use of adjuvant therapy. “The data support and other studies have shown a more general decline in death rates among women diagnosed after 1980,” said Dr. Mettlin.

He cautioned, however, that the decline in death rates is not seen in all regions. “For example, the favorable trends in northern Europe are not evident in Spain, Portugal, Greece, Hungary, Poland, and Italy. Also, in Japan, where breast cancer death rates have been low, mortality is increasing as the disease becomes more common among Japanese women.”

Dr. Mettlin feels that viewing breast cancer mortality globally reveals features that may not be seen by viewing data from individual countries or regions. “The severalfold difference in risk between countries in North America and northern Europe compared to Asian regions, for example, suggests that environmental factors may be profoundly involved in the etiology of the disease.” He advocates expanding the network of cancer registries and reporting systems that make these observations possible for future monitoring of worldwide progress against the disease