"ABSTRACT

Introduction

Increasing epidemiological evidence suggests that diabetes is associated with a modest but significant elevation in breast cancer risk, as well as poorer clinical outcomes following diagnosis. This integrative review critically synthesizes current epidemiological, biological and clinical evidence to elucidate the role of diabetes in breast cancer development and progression among women.

Methods

We conducted a structured literature search (2010–2025) to identify original studies examining the relationship between diabetes and breast cancer risk and outcomes. English‐language human studies were included. Titles, abstracts and full texts were screened against predefined criteria, and relevant data were extracted and synthesized narratively.

Results

Studies indicate that women with diabetes experience an increased incidence of breast cancer, with stronger associations observed in postmenopausal populations, and partial attenuation of risk following adjustment for obesity, highlighting both shared and independent metabolic contributions. Mechanistically, chronic hyperinsulinemia, altered insulin‐like growth factor signalling, low‐grade systemic inflammation, oxidative stress and oestrogen‐metabolic crosstalk are frequently proposed as biologically plausible pathways through which diabetes may influence breast carcinogenesis, particularly in hormone‐receptor‐positive tumours. Clinically, diabetes has been linked to delayed diagnosis, increased treatment‐related complications, and higher breast cancer‐specific mortality, underscoring the need for integrated metabolic and oncologic care.

Conclusion

Diabetes mellitus, particularly type 2 diabetes, is consistently associated in observational studies with a small increment in breast cancer risk and a more clearly adverse impact on survival. Mechanistic and translational evidence supports biologically plausible pathways linking metabolic dysregulation to tumour initiation, progression and treatment tolerance, but definitive causal effects remain uncertain. Medication and biomarker‐based research and practice should be incorporated in metabolic‐oncologic care and research to enhance prevention and outcomes.

Keywords: breast cancer risk, diabetes, epidemiology, incidence, mortality, prognosis"