Breast cancer is the most common cancer amongst women and is the leading cause of cancer-related deaths in women between the ages of 35 to 54 years old. While breast cancer can also occur in younger woman, it very uncommon—only 1.8% of all cases are diagnosed in women from 20 to 34 years old and only 10% in woman from 35 to 44 years old.
However, in a study released in The Journal of the American Medical Association in February 2013, researchers reported that the incidence of advanced breast cancer may have increased among younger women, ages 25 to 39. While the findings need to be verified by further research, the study found that advanced cases rose from 1.53 per 100,000 women in 1976 to 2.9 per 100,000 women in 2009. This finding points to an increase of 1.37 cases per 100,000 women in 34 years. While the absolute increase of 1.37 cases per 100,000 is relatively small, the increase is statistically significant. Further, the study demonstrates that there is no evidence of abatement.
The connection between environmental risk factors and breast cancer is not a new area of research. For decades, epidemiological and experimental findings have indicated that environmental pollutants—chemicals from pharmaceuticals, pesticides, insecticides, manufacturing, and gasoline known as “endocrine disruptors” —may affect the incidence of breast cancer in women given their effects on mammary gland development. Furthermore, breast cancer rates in non-industrialized countries are lower than in industrialized countries, suggesting that the presence of industrial processes and pollutants influence the incidence of breast cancer.
The finding of a higher frequency of breast cancer in younger women is alarming from both a human health and environmental perspective. First, breast cancer found in younger woman tends to be more deadly— “young age itself is an independent adverse prognostic factor for breast cancer.” For example, the 5-year survival rate for distant disease for 25 to 39 year old women is only 31%. Additionally, because breast cancer has been relatively uncommon in younger women, the finding that there has been an increased incidence of advanced breast cancer in younger women suggests that there are external environmental factors affecting this increase. Thus, this finding should spur additional research in the connection between environmental risk factors and breast cancer to prevent, reduce, and abate the prevalence of this deadly cancer, particularly in younger women.