LAUSR

Highlights • A prospective pilot phase I/II study on metformin given concurrently with neoadjuvant chemoradiation (CRT) in non-diabetic rectal cancer patients.• Three patients had a clinical complete response (cCR) and did not have surgical resection.• Of the 12 patients who underwent surgery, there were two pCRs. For the combined pCR/cCR rate of 33% (95% CI 19–47%), a total of 85 patients will be required to yield a 95% CI with a 10% margin of error.• These pilot results are encouraging, and will serve to refine the design and conduct of a future phase 2 trial to determine whether adding metformin to CRT improves pCR/cCR rates.