Breast cancer is the most common malignancy among women and its incidence continues to rise globally. Coexisting Type 2 diabetes mellitus (T2DM) is a frequent comorbidity that can adversely affect breast cancer outcomes. Metformin, the guideline-recommended first-line agent for T2DM, has been proposed to possess antineoplastic effects and to alter cancer progression and treatment response. The present study evaluated whether metformin use is associated with differences in demographic, pathological, and clinical outcomes among breast cancer patients with T2DM in an Iranian clinical population.
This was a retrospective cross-sectional analysis of medical records for 104 patients diagnosed with both breast cancer and T2DM who received care at the Velayat Educational and Therapeutic Center, Qazvin, Iran, between 2019 and 2023. Patients were categorized into two groups based on recorded antidiabetic treatment: metformin users (n = 46) and non-metformin users (n = 58). Extracted variables included demographic characteristics, disease duration, disease stage at presentation, lymph node involvement, hormone receptor status (including estrogen receptor [ER]), HER2 status, treatment response, prognosis, recurrence, and metastasis.
Statistical analyses were performed with SPSS version 25. Group comparisons were assessed with appropriate univariate tests and statistical significance was set at p < 0.05. Both unadjusted and adjusted logistic regression analyses were used to identify independent predictors of prognosis. The abstract reports principal comparisons and which variables remained associated with prognosis after adjustment; the exact list of covariates included in adjusted models is reported in the full article rather than the abstract.
Among the 104 patients, 46 were recorded as metformin users and 58 as non-users. Key findings reported in the abstract include:
Mean disease duration: Significantly shorter in metformin users compared with non-metformin users (p = 0.036).
Disease stage: Metformin users were more often diagnosed at earlier stages of disease; the difference in distribution of stage between groups reached statistical significance (p = 0.003).
Lymph node involvement: The proportion of patients with lymph node involvement was significantly lower in the metformin group (p = 0.008).
Treatment response: Patients using metformin demonstrated a significantly better treatment response compared with non-users (p = 0.028).
Prognosis: Overall prognosis was significantly more favorable in the metformin group (p = 0.009).
Hormone receptors and outcomes without association: No significant differences were observed between metformin users and non-users for ER status (p = 0.293), HER2 status (p = 0.762), metastasis rates (p = 0.249), or recurrence rates (p = 0.770).
Figure 1 in the source compares clinicopathological characteristics between metformin users and non-users and visually summarizes the higher proportion of early-stage disease, lower lymphatic involvement, improved treatment response, and better prognosis among metformin users.
The authors performed multivariable logistic regression to control for potential confounders. After adjustment, three variables remained independently associated with prognosis: disease duration, HER2 status, and metformin use. The abstract does not list the full set of covariates included in the model, the adjusted odds ratios, or confidence intervals; those details are provided in the full text.
In this retrospective cohort of Iranian breast cancer patients with T2DM, recorded use of metformin was associated with presentation at an earlier disease stage, fewer involved lymph nodes, better treatment response, and improved prognosis. No significant associations were found with ER or HER2 receptor distribution, metastasis, or recurrence in unadjusted comparisons, although HER2 status was an independent predictor of prognosis in adjusted analysis alongside metformin use and disease duration.
The authors conclude that metformin may have a beneficial role in breast cancer progression and treatment outcomes among patients with T2DM, and they recommend prospective studies to confirm these associations and to investigate underlying mechanisms. The abstract notes that further clinical research is warranted; specifics such as metformin dosing, duration of therapy, and detailed model covariates were not reported in the abstract and require consultation of the full article for comprehensive assessment.
Conflict of interest
The authors declared no conflicts of interest in the source article.
Keywords
breast cancer, metformin, Type 2 diabetes mellitus, lymph node involvement, prognosis