Adding metformin to chemoradiotherapy does not improve efficacy and may increase toxicity in patients with non-small cell lung cancer (NSCLC), according to a pair of phase 2 trials published in JAMA Oncology.

In the OCOG-ALMERA trial ( Identifier: NCT02115464), metformin was associated with an increase in treatment failure and toxicity, as well as worse progression-free survival (PFS) and overall survival (OS).1

In the NRG-LU001 trial ( Identifier: NCT02186847), PFS, OS, and toxicity outcomes were similar between the metformin and control arms.2

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The OCOG-ALMERA study included 54 patients with unresected, locally advanced NSCLC who did not have diabetes. The patients were randomly assigned to receive platinum-based chemotherapy and concurrent chest radiotherapy with or without consolidation (n=28) or the same treatment plus 2000 mg per day of metformin (n=26).

The primary outcome was the proportion of patients who failed treatment within 12 months, with failure defined as disease progression, distant metastasis, death, or discontinuation for any reason.

The rate of treatment failure was 69.2% in the metformin arm and 42.9% in the control arm (P =.05).

The 1-year PFS rate was 34.8% in the metformin arm and 63.0% in the control arm (hazard ratio [HR], 2.42; 95% CI, 1.14-5.10). The OS rate was 47.4% and 85.2%, respectively (HR, 3.80; 95% CI, 1.49-9.73).

The rate of grade 3 or higher adverse events (AEs) was 53.8% in the metformin arm and 25.0% in the control arm. The most common AEs in the metformin arm were esophagitis (19.2%) and lung infection (23.1%).

“[T]he addition of metformin to chemoradiotherapy was associated with worse treatment efficacy and increased toxic effects compared with combined modality therapy alone,” the study authors wrote. “Metformin is not recommended in patients with [locally advanced] NSCLC who are candidates for chemoradiotherapy.”