Impact of timing and breastfeeding on postpartum breast cancer diagnostic patterns and outcomes.

Purpose: Postpartum breast cancers (PPBC) have a worse prognosis than other breast cancers, but the impact of timing postpartum (PP) and concurrent breastfeeding (BF) on diagnostic patterns and outcomes remains unclear.

Methods: We analyzed 161 PPBC patients diagnosed from 2002 to 2014, hypothesizing that diagnosis < 2 years PP (vs 2-5 years) and concurrent BF (vs not BF) at diagnosis would be associated with delayed diagnosis. We compared 2-year PP patients (N = 60) and 2-5 year PP patients (N = 101), and subsequently, patients who were (n = 36) and were not (n = 24) BF at diagnosis among the 2-year PP group with respect to clinicopathologic characteristics, breastfeeding details, diagnostic patterns, and disease outcomes. Differences were evaluated using chi-square and Mann-Whitney tests. Kaplan-Meier analysis assessed overall survival (OS) and distant disease-free survival (DDFS).

Results: Median follow-up was 54 months. Patients in the 2-year PP group were more likely to be BF at diagnosis (60% vs 7%, p < 0.001), and have their symptoms attributed to lactational change (37 vs 9%, p < 0.001). They were also diagnosed at a higher stage (43 vs 24% Stage III/IV, p = 0.01), had worse 5-year OS (79% vs 97%, p < 0.001), and DDFS (74% vs 93%, p = 0.003) compared to 2-5 year PP patients. Among 2-year PP patients, patients BF at diagnosis were more likely to be diagnosed with mastitis preceding diagnosis (31% vs 4%, p = 0.03), more often had their symptoms attributed to lactational change (58% vs 4%), trended toward higher stage at diagnosis (53 vs 29% Stage III/IV, p = 0.1), had significantly worse 5-year DDFS (62% vs 91%, p = 0.032), and trended toward worse OS (74% vs 86%, p = 0.08) compared to those not BF.

Conclusions: Our findings suggest that early PPBC and BF at diagnosis are associated with diagnostic delay and higher stage at diagnosis, which may have implications for prognosis.