Metformin improves survival in patients with concurrent diabetes and small cell lung cancer: a meta-analysis.

Introduction: To compare survival outcome among the patients with concurrent small cell lung cancer (SCLC) and diabetes mellitus (DM) using metformin or without metformin.

Evidence acquisition: A systematic literature search for relevant studies up to Oct 2020 was conducted. Outcome of the included studies included overall survival (OS) or disease-free survival (DFS). HR values were pooled to estimate the effect of metformin on survival outcomes.

Evidence synthesis: Six studies with 539 participants with both SCLC and diabetes were included in the analysis. The patients with metformin usage had significantly longer OS and DFS than those without metformin usage (OS: HR=0.72 [0.53-0.98], P=0.04; DFS: HR=0.59 [0.45-0.76], P<0.0001). The studies included were not significantly different in the two analyses by heterogeneity test. There was no obvious publication bias.

Conclusions: Metformin may improve survival among patients with concurrent SCLC and DM. Further investigations especially randomized control trials are warranted, especially among the patients who do not have diabetes.