Metastatic breast cancer on the rise in young women
According to a new study, the incidence of metastatic breast cancer, which is the most advanced form of the disease, has increased among younger women between the ages of 24 and 39. In addition, some ethnic disparities were found. The findings were published on February 27 in the Journal of the American Medical Association (JAMA) by researchers affiliated with the University of Washington (Seattle, Washington) and St. Charles Health System (Bend, Oregon).
The researchers noted that evidence from the US National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) database suggests that the incidence of advanced breast cancer in young women is increasing. Therefore, they designed a study with the objective of quantifying this trend and analyze it as a function of stage at diagnosis, race/ethnicity, residence, and hormone receptor status.
The researchers reviewed data regarding breast cancer incidence, incidence trends, and survival rates as a function of age and extent of disease at diagnosis from three SEER registries; the data spanned three time intervals: 1973-2009, 1992-2009, and 2000-2009. SEER defines localized breast cancer as disease confined to the breast, regional breast cancer to contiguous and adjacent organ spread (i.e., lymph nodes, chest wall), and distant disease to remote metastases (i.e., bone, brain, lung). The main outcome measure was the assessment of breast cancer incidence trends in the United States.
The investigators found that in the U.S., the incidence of breast cancer with distant involvement at diagnosis increased in 25- to 39-year-old women from 1.53 per 100,000 in 1976 to 2.90 per 100,000 in 2009. They noted that this difference represented an absolute difference of 1.37 per 100,000, representing an average compounded increase of 2.07% per year (1.57% to 2.58%) over the 34-year interval. No other age group or extent-of-disease subgroup of the same age range had a similar increase. For 25- to 39-year-olds, there was an increased incidence in distant disease among all races and ethnicities evaluated, especially non-Hispanic white and African American, and this occurred in both metropolitan and nonmetropolitan areas. In addition, the incidence for women with estrogen receptor–positive subtypes increased more than for women with estrogen receptor–negative subtypes.
The researchers concluded that, based on SEER data, there was a small but statistically significant increase in the incidence of breast cancer with distant involvement in the United States between 1976 and 2009 for women aged 25 to 39 years, without a corresponding increase in older women.
Prognosis estimates for metastatic breast cancer have improved significantly in the last few decades; however, according to the National Cancer Institute, the five-year survival rate for this stage of breast cancer is still fairly low at 23.8%. In addition, the difference in survival between women with metastatic breast cancer and women diagnosed with either regional or localized disease is approximately 55%
Take home message:
The researchers did not offer an explanation for the increase in metastatic breast cancer among young women; however, a February 19, 2013 report by the World Health Organization (WHO) does offer an explanation. The agency noted that a global surge in birth defects, hormonal cancers, and psychiatric illnesses has occurred. The WHO claims that man-made chemicals in everyday products are likely to be at least partially responsible for the increase. The new report updated a 2002 study on the potential dangers of synthetic chemicals. The authors noted that the situation was “a global threat that needs to be resolved.” It claimed that humans and animals across the planet were probably exposed to hundreds of these often little-studied or understood compounds at any one time. The investigators wrote: “We live in a world in which man-made chemicals have become part of everyday life.