Migrant Studies Aid the Search for Factors Linked to Breast Cancer Risk

Extract

Breast cancer is by far the most common nonskin cancer in U.S. women. However, breast cancer rates vary widely around the world. Most cases occur in industrialized countries in Europe and North America, whereas the disease is less common among developing countries in Africa and Asia. Rates in the Netherlands, France, Denmark, and the United States, for example, cluster around 90–100 cases per 100,000 women, whereas those in China, India, Turkey, and Rwanda range from 10–20 cases per 100,000 women.

Over the past four decades, many studies have shown that breast cancer rates change when women move to a new country, providing evidence for the importance of lifestyle and environment in breast cancer risk. However, most of the studies have not been designed to answer questions about which factors are driving the increased risk.

Now, data from several recent studies of people who have migrated from their home countries are beginning to suggest some answers. “Migration provides a kind of natural experiment allowing the comparison of populations of similar genetic background living in different environments,” said Max Parkin, M.D., an epidemiologist at the University of Oxford in the United Kingdom.