A study published today in the Journal of the American Medical Association cites a troubling trend: the number of young women, age 25-39, being diagnosed with advanced (metastatic) breast cancer appears to be rising steadily over time. As a young woman, what does this mean to you? Earlier mammograms? More stress? Or simply “knowledge is power”?

The vast majority of breast cancer diagnoses – greater than 90% – come in women over the age of 40. 

So, if you’re a woman under age 40, you basically don’t need to worry about breast cancer – right? Sure, be alert to a new lump in your breast, but really, breast cancer is way down the list of health issues you need to concern yourself with.

Right?

Not so fast. The study noted above, tracking over 900,000 women for upwards of 35 years (1976-2009), reveals that, while the incidence of advanced breast cancer is still small in young women, it’s rising steadily.  

In 1976, an average of 1.53 women per 100,000, age 25-39, were diagnosed with advanced (metastatic) breast cancer – a.k.a. stage IV cancer, disease that had spread beyond the breast and adjacent lymph nodes to other organs: principally lungs, brain, liver, or bones.

By 2009, an average of 2.9 women per 100,000 in that same age group were being diagnosed with metastatic breast cancer. 

That’s a near doubling of cases – but the absolute number is still tiny. So why should this data be troubling?

Because the rate of increase shows no sign of slowing down, despite greater breast cancer awareness, and improvements in screening and diagnosis.

According to the authors of the study, “The trajectory of the incidence trend predicts that an increasing number of young women in the United States will present with metastatic breast cancer in an age group that already has the worst prognosis, no recommended routine screening practice, the least health insurance, and the most potential years of life.” (Bernal, 2013)

In other words, going forward, more and more women under age 40 will be diagnosed with incurable breast cancer. And these women arguably have the most to lose (many potential years of life; often mothers of young children); with the fewest defenses (no routine screening; more likely to be uninsured or under-insured).

What’s behind this trend? Deputy Chief Medical Officer of the American Cancer Society, Dr. Len Lichtenfeld, surmises that the change might involve the later age at which many American women are giving birth to their first child; the earlier a woman has children, the greater her protection against breast cancer. Lichtenfeld also speculated that toxic chemicals in the environment might be to blame. (Knox, 2013)

But Lichtenfeld also advised women not to over-react. "When people hear about research like this, they tend to become far more concerned than the numbers reflect," he says. "These are very small numbers.” (Knox, 2013)