The following article features coverage from the San Antonio Breast Cancer Symposium (SABCS) 2017 meeting. Click here to read more of Cancer Therapy Advisor‘s conference coverage.

Adding metformin to neoadjuvant chemotherapy with trastuzumab did not significantly improve the pathological complete response (pCR) rate among patients with HER2-positive, early-stage breast cancer, according to findings being presented at the 2017 San Antonio Breast Cancer Symposium.1

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Previous studies suggest that metformin, which is used to treat diabetes, benefits patients with breast cancer. The purpose of this phase 2 study was to assess the effect of adding metformin to first-line breast cancer therapy.

Researchers randomly assigned 84 women with HER2-positive breast cancer to receive metformin 1700 mg for 6 months concurrently with weekly paclitaxel for 12 cycles plus trastuzumab, followed by 4 cycles of fluorouracil, epirubicin, and cyclophosphamide plus trastuzumab (Arm A, 41 patients), or an equivalent chemotherapy regimen plus trastuzumab without metformin (Arm B, 43 patients). Study patients were to undergo surgery upon completion of treatment.

Results showed that 65.5% (95% CI, 47%-80%) of patients in Arm A had a pCR compared with 58.6% (95% CI, 41%-74%) of patients in Arm B (odds ratio [OR], 1.34; 95% CI, 0.46-3.89; P = .589). Patients in Arm A and Arm B had a combined pCR/near-pCR of 79.3% and 72.4%, respectively.

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The most frequently reported adverse events in the entire cohort were diarrhea, nausea, mucositis, liver function–related events, alopecia, sensory neuropathy, neutropenia, and fatigue. Ninety percent of these events were grade 1 or 2.

Seven patients had left ventricular ejection fraction decreases, though only 1 patient progressed to symptomatic heart failure.

The authors concluded that “[e]valuation of long-term outcome data such as 5-year disease-free survival and correlative biological studies are needed to evaluate the clinic-molecular relevance of these findings.”

Read more of Cancer Therapy Advisor‘s coverage of the San Antonio Breast Cancer Symposium (SABCS) 2017 meeting by visiting the conference page.


  1. Pernas S, Dorca J, Álvarez-López I, et al. Safety and efficacy of neoadjuvant metformin with trastuzumab and chemotherapy in women with HER2-positive early breast cancer: A randomized, open-label, multicenter, phase 2 trial. Poster presented at: 2017 San Antonio Breast Cancer Symposium (SABCS); December 5-9, 2017; San Antonio, TX.