Breast cancer incidence in women aged 25 to 39 has been steadily increasing for the last 80 years, with the increase beginning at least a decade before the baby boom, according to a study published in JAMA Network Open.
The researchers also suggested that this increase cannot be attributed to changes in parity over time.
“Because our age of interest is younger than 40 years, the significant increase in breast cancer incidence also cannot be explained by increased mammography starting in the 1970s,” the authors wrote. “The trend analysis also shows that the increase in breast cancer began long before routine mammography was initiated.”
In this population-based cohort study, researchers used aggregate-level data from the Connecticut Tumor Registry (CTR), the oldest population-based registry in the US, to look at breast cancer incidence and age-standardized rates among women…