We aimed to evaluate the role of breastfeeding as a risk factor of IBC compared to non-IBC and according to hormonal (HR) and human epidermal growth factors receptors (HER2) receptor status.
Cases of IBC (n = 160) and controls of non-IBC (n = 580) were collected from the cohort of breast cancer patients treated in two oncology centers 1:1 matched on the basis of age at cohort entry (+-2 years). Data about breastfeeding were collected, association and odds ratios were calculated. Breastfeeding was also evaluated in 3 further sub-groups: (HR+, HER2-), (HER2+, HR-) and triple negative (TN) patients.
Breastfeeding rate was similar between IBC and non-IBC patients (62% vs 65.3%, p = 0.57). However, breast feeding duration>12months was significantly more common in IBC vs non-IBC (30% vs 8.4%, p = 0.01). This observation was also confirmed in HR positive (32.5% vs 9.2%, p < 0.01) and HER2 positive (35.8% vs 6.35%, p < 0.01) but not in TN groups (24.3 vs 10.7, p = 0,06). We did not observe an association between breast feeding and occurrence of IBC, with an odds ratio of 1.1 [95% confidence interval (CI) 0.7-1.8], neither among HR+, HER2+ and TN groups. Odds ratio for developing IBC in breast feeding duration>12 months relative to shorter duration was 4.6 [2.9-7.2]. In HR+ tumors, it was 3.5 [1.5-8.1], and in HER2+ it was 5.7 [3-10.7]. However in TN tumors, odds ratio was not significant (2.6 [0.9-7.4]).
Patients with breastfeeding duration>12 months, were 4.6 times more likely to develop IBC compared to non IBC. This risk became 3.5 times in HR+ and 5.7 times in HER2.This observation was not confirmed in TN tumors.
Abderrahmen Mami Hospital.
Has not received any funding.
All authors have declared no conflicts of interest.