First mammogram-detected cancers portend worse survival in young women diagnosed with breast cancer.

Purpose: Breast cancer (BC) screening guidelines for women ages 40-45 have differed across multiple organizations, resulting in variable ages of screening commencement among women in the US. We previously reported that delay in screening beyond age 40 increases risk for first mammogram cancer diagnoses. We hypothesize that first mammogram cancer detection may also diminish recurrence-free and overall survival (RFS, OS).

Study design: This retrospective cohort study included 738 women diagnosed with BC from ages 40-45 years and treated within a single hospital system from 2010 to 2019. First mammogram cancers were defined as those with tissue diagnoses established within 3 months of baseline mammogram. RFS after surgery and OS after BC diagnosis were analyzed in patients diagnosed on first versus subsequent mammograms via the Kaplan-Meier method, with p-values generated by log rank tests. Cumulative incidences of local and distant recurrence were also assessed.

Results: Of 738 women, 218 had first mammogram cancers while 520 were diagnosed on subsequent mammograms. Median follow-up was 72.2 months (0.5-155.8 months). At 5 and 10 years after diagnosis, OS was significantly worse in patients diagnosed on their first mammogram (0.88 [0.83-0.93] and 0.80 [0.73-0.87]) versus subsequent mammograms (0.95 [0.93-0.97] and 0.90 [0.86-0.93]), p = 0.003. Patients with first mammogram cancers also had inferior 5- and 10-years RFS rates (0.81 [0.71-0.88] and 0.74 [0.65-0.83] vs. 0.88 [0.85-0.92] and 0.77 [0.72-0.83]), p = 0.04.

Conclusion: First mammogram cancers were associated with worse survival in our study cohort, reinforcing the importance of consistent guidelines for screening commencement at age 40.