Age and Sex in Breast Cancer: Moving Beyond a One-Size-Fits-All Approach

Breast cancer is not a uniform disease. Despite decades of research showing that age and sex shape breast cancer biology and treatment response, clinical and research frameworks continue to rely on a one-size-fits-all approach. Too often, we extrapolate findings from one population to another, assuming that what works for one group will work just as well for another. Ignoring age and sex variables has real consequences. Older adults, who make up the majority of breast cancer cases, are still underrepresented in clinical trials, leaving us with gaps in knowledge about how best to treat them. Male breast cancer is still treated largely by analogy to female breast cancer despite growing evidence that the 2 diseases have distinct molecular features. Here, we discuss a framework on the relationships between age and sex with regard to breast cancer biology and treatment to advance precision medicine and optimize patient outcomes.