Does Mastitis Increase the Risk of Breast Cancer? A Systematic Review and Meta-Analysis

Background: Breast cancer (BC), is the most prevalent malignant neoplasm in women. There are well-established risk factors such as family history, genetic mutations, among others. Several inflammations have been confirmed to be associated with an increased risk of malignancy but the correlation between Mastitis and BC isn’t clear. So, this study aims to explore mastitis as a potential risk factor for BC. Methods: We performed a systematic review and meta-analysis with case control (CC) and cohort studies (CS). PubMed, Scopus, Web of Science, and the Cochrane Library databases were searched for eligible studies. Statistical meta-analyses (MA) were performed in R Studio 4.4.2 software, to calculate the odds ratio (OR) and de Hazard ratio (HR), we considered statistically significant values with P less than 0.05, with a confidence interval (CI) of 95%. I² statistics were used to calculate heterogeneity between studies. Results: Four studies were included in this MA, three CS and one CC, involving a total of 51,125 patients;. The statistical analyses results showed that in the four studies the incidence of breast cancer was increased in patients with mastitis, (OR 2.12; 95% CI 1.44–3.11; P = 0.0423; I² = 63.4%). Analyzing HR it shows that the incidence of BC was increased in the MG, (HR 2.0421; 95% CI 1.16–3.58; p < 0.01). I² = 80.7%, p = 0.0056). Conclusions: Our findings suggest that women with a history of mastitis face a substantially elevated risk of developing BC.