Comparison of patients with small (≤2 cm) breast cancer according to adherence to breast screening program

Background
We investigated whether adherence to breast screening would yield a clinical benefit even among patients with small breast cancer (≤2 cm) by comparing differences between those who did and did not adhere to breast screening.
Methods
Patients who were diagnosed with invasive T1 breast cancer and treated at Gangnam Severance Hospital from January 2006 to June 2014 were included. Of the 632 study patients, 450 and 182 were classified as screen-adherent and non-adherent. Adherence to the breast screening program was defined as the completion of breast screening examinations within 3 years before cancer diagnosis. Recurrence-free survival (RFS) and metastasis-free survival (MFS) were compared between the groups. Propensity score matching were applied to compare survival outcome.
Results
Adherent patients were more likely to have a lower histologic grade (P < 0.001), high estrogen receptor expression (P = 0.040), and lower HER2-positivity (P = 0.026). The adherent group had more favorable subtypes compared to the non-adherent group, with a greater percentage of Luminal/HER2-negative subtype (66.7% vs. 56.5%) and a lower percentage of HER2 subtype (8.3% vs. 16.7%). The RFS and MFS were significantly better in the adherent group (P = 0.003, 0.010, respectively). In the case-matched cohort, superior survival of the adherent group was maintained.
Conclusions
Adherence to breast screening in patients with small breast tumors was associated with more favorable tumor biology and better prognosis. Our findings suggest that adherence to breast screening might offer clinical benefits in terms of tumor biology as well as early detection.