A Trial of Standard Chemotherapy With Metformin (vs Placebo) in Women With Metastatic Breast Cancer

A double blind Phase II randomized study of metformin versus (vs) placebo in non-diabetic women on first to fourth line chemotherapy with anthracycline, taxane, platinum, capecitabine or vinorelbine based regimens for metastatic or unresectable locally advanced breast cancer (BC). Patients were randomized to receive metformin 850 mg tablets or placebo once daily for two days as ramp-up, followed by one tablet twice a day for the duration of the study. Randomization was stratified by line of chemotherapy (1st, 2nd, 3rd and 4th line) and hormone receptor status (ER and/or PgR positive versus both negative). All patients were required to have measureable or non-measureable, but evaluable metastases at study entry. Metformin or placebo was to be continued until disease progression, even if chemotherapy was changed or stopped prior to disease progression. Recruitment took place at five sites in Ontario, Canada: Mount Sinai Hospital, Princess Margaret Cancer Centre, St. Michael's Hospital, Toronto and London Regional Cancer Centre, London.