The Effect of Metformin on Chemotherapy-Induced Toxicities in Non-diabetic Breast Cancer Patients: A Randomised Controlled Study

Background and Objective Breast cancer patients treated with adriamycin-cyclophosphamide plus paclitaxel (AC-T) are often challenged with serious adverse effects for which no effective therapies are available.

Here, we investigated whether metformin, an antidiabetic drug with additional pleiotropic effects could favourably offset AC-T induced toxicities.

Patients and Methods Seventy non-diabetic breast cancer patients were randomised to receive either AC-T (adriamycin 60 mg/m^2 + cyclophosphamide 600 mg/m^2 × 4 cycles Q21 days, followed by weekly paclitaxel 80 mg/m^2 × 12 cycles) alone or AC-T plus metformin (1700 mg/day).

Patients were assessed regularly after each cycle to record the incidence and severity of adverse events based on the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE), version 5.0.

Moreover, baseline echocardiography and ultrasonography were done and repeated after the end of neoadjuvant therapy.

Results Addition of metformin to AC-T resulted in significantly less incidence and severity of peripheral neuropathy, oral mucositis, and fatigue ( p < 0.05) compared to control arm.

Moreover, the left ventricular ejection fraction (LVEF%) in the control arm dropped from a mean of 66.69 ± 4.57 to 62.2 ± 5.22% ( p = 0.0004) versus a preserved cardiac function in the metformin arm (64.87 ± 4.84 to 65.94 ± 3.44%, p = 0.2667).

Furthermore, fatty liver incidence was significantly lower in metformin compared with control arm (8.33% vs 51.85%, p = 0.001).

By contrast, haematological disturbances caused by AC-T were preserved after concurrent metformin administration ( p > 0.05).

Conclusion Metformin offers a therapeutic opportunity for controlling toxicities caused by neoadjuvant chemotherapy in non-diabetic breast cancer patients.

Trial Registration This randomised controlled trial was registered on November 20, 2019 in ClinicalTrials.gov under registration number: NCT04170465.