OBJECTIVETo evaluate the colorectal cancer (CRC) prevention effect of metformin in comparison with that of other T2DM medications from a Markov model perspective.

METHODSLiterature concerning CRC morbidity of T2DM patients with metformin or other diabetes medications treatment was reviewed in PubMed and Cochrane Library database from September 2010 to December 2016.

INCLUSION CRITERIA(1)enrolled population was adult patients with T2DM but without CRC; (2) any of the parameters applied in our model was reported; (3) randomized clinical trials (RCTs), quasi-randomized trials, prospective or retrospective cohort studies. With CRC morbidity as endpoint, parameters were extracted to construct Markov model to assess CRC morbidity and cumulative tumor-free survival in each group over 11 years' follow-up period. Finally, Monte Carlo analysis was performed to evaluate the influence of parameter instability on the model.

RESULTSSeven literatures were recruited and 10 000 patients were virtually allocated for each arm. In contrast with non-metformin group, T2DM patients treated with metformin had a lower rate of CRC(1.670% vs. 2.146%, P=0.016). Moreover, cumulative tumor-free survival of metformin group was, slightly but significantly, better than that of non-metformin group (10.908 years vs. 10.882 years, P=0.000).

CONCLUSIONST2DM patients treated with metformin have a lower morbidity of CRC and a better cumulative tumor-free survival than those of non-metformin group. Large scale RCTs are needed to illustrate the role of metformin in the prevention of CRC.