Breast cancer in women under age 40: A decade of trend analysis at a single institution.

Abstract Background Women should be evaluated for breast cancer risk by age 30 to assess for screening need. Recent trends in breast cancer in this population may further inform recommendations. Objective The aim of this study was to analyze trends over time in the rate of breast cancer, tumor characteristics and treatment in women under age 40. Methods Retrospective cohort study of women under age 40 at our institution diagnosed with breast cancer from January 2007 to April 2018 was conducted. Patient demographics, tumor characteristics and treatment outcomes were collected. Descriptive statistics and the Mann-Kendell Trend test were calculated. Two-proportion z-tests were used to compare proportions of stage, pathology and treatment between 2007-2013 and 2014–2018. Results 197 women under age 40 were treated for a new diagnosis of breast cancer at our institution. A higher proportion of women were diagnosed with invasive carcinoma in 2013–2018 (91%) compared to 2007–2012 (78%), p = 0.008. A higher proportion of women were diagnosed with advanced stage disease (stage III-IV) in 2013–2018 (24%) compared to 2007–2012 (2%), p = 0.001. No statistically significant evidence for an increasing trend of overall rate of breast cancer over the last 11 years (p = 0.419) was observed. Conclusions While no statistically significant increase in overall rate of breast cancer was noted, an increase in invasive and later staged breast cancers was observed. Clinical impact Rise in more aggressive cancers in a population that is largely not screened may have implications both on the individual young woman's morbidity as well as on a public health level.