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

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.

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).

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.

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.