***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Aims /hypothesisObservational and mechanistic studies have suggested a possible relationship between treatment with metformin and decreased incidence of cancer in participants with type 2 diabetes . We extracted data for malignancies from the ADOPT ( A Diabetes Outcome Progression Trial ) and RECORD ( Rosiglitazone Evaluated for Cardiovascular Outcomes and Regulation of Glycaemia in Diabetes ) r and omised controlled clinical trials , in which the efficacy and /or safety of metformin was assessed in comparison with sulfonylureas and rosiglitazone . Methods Neoplasm occurrences were collected as adverse events in these studies . We review ed and re-analysed the individual participant data in both studies for serious adverse events , malignancies reported as adverse events and related neoplasms of special interest . Results In ADOPT , 50 participants ( 3.4 % ) on  metformin  and 55 ( 3.8 % ) on each of rosiglitazone and glibenclamide ( known as glyburide in the USA and Canada ) developed serious adverse event malignancies ( excluding non-melanoma skin cancers ) . This corresponds to 1.03 , 1.12 and 1.31 per 100 person-years , giving hazard ratios for metformin of 0.92 ( 95 % CI 0.63–1.35 ) vs rosiglitazone and 0.78 ( 0.53–1.14 ) vs glibenclamide . In RECORD , on a background of sulfonylurea , 69 ( 6.1 % ) participants developed malignant neoplasms in the metformin group , compared with 56 ( 5.1 % ) in the rosiglitazone group ( HR 1.22 [ 0.86–1.74 ] ) . On a background of metformin , 74 ( 6.7 % ) participants in the sulfonylurea group developed malignant neoplasms , compared with 57 ( 5.1 % ) in the rosiglitazone group ( HR 1.33 [ 0.94–1.88 ] ) . Conclusions /interpretationThe malignancy rates in these two r and omised controlled clinical trials do not support a view that metformin offers any particular protection against malignancy compared with rosiglitazone . However , they do not refute the possibility of a difference compared with sulfonylureas OBJECTIVE The antidiabetic properties of metformin are mediated through its ability to activate the AMP-activated protein kinase ( AMPK ) . Activation of AMPK can suppress tumor formation and inhibit cell growth in addition to lowering blood glucose levels . We tested the hypothesis that metformin reduces the risk of cancer in people with type 2 diabetes . RESEARCH DESIGN AND METHODS In an observational cohort study using record-linkage data bases and based in Tayside , Scotl and , U.K. , we identified people with type 2 diabetes who were new users of metformin in 1994–2003 . We also identified a set of diabetic comparators , individually matched to the metformin users by year of diabetes diagnosis , who had never used metformin . In a survival analysis we calculated hazard ratios for diagnosis of cancer , adjusted for baseline characteristics of the two groups using Cox regression . RESULTS Cancer was diagnosed among 7.3 % of 4,085 metformin users compared with 11.6 % of 4,085 comparators  , with median times to cancer of 3.5 and 2.6 years , respectively ( P < 0.001 ) . The unadjusted hazard ratio ( 95 % CI ) for cancer was 0.46 ( 0.40–0.53 ) . After adjusting for sex , age , BMI , A1C , deprivation , smoking , and other drug use , there was still a significantly reduced risk of cancer associated with metformin : 0.63 ( 0.53–0.75 ) . CONCLUSIONS These results suggest that metformin use may be associated with a reduced risk of cancer . A r and omized trial is needed to assess whether metformin is protective in a population at high risk for cancer Background : Experimental studies have suggested that metformin may decrease the incidence of colorectal cancer in patients with type II diabetes . However , previous observational studies have reported contradictory results , which are likely due to important method ologic limitations . Thus , the objective of this study was to assess whether the use of metformin is associated with the incidence of colorectal cancer in patients with type II diabetes . Methods : A cohort study of patients newly treated with non-insulin antidiabetic agents  was assembled using the United Kingdom Clinical Practice Research Data link . A nested case – control analysis was conducted , where all incident cases of colorectal cancer occurring during follow-up were identified and r and omly matched with up to 10 controls . Conditional logistic regression was used to estimate adjusted rate ratios ( RR ) of colorectal cancer associated with ever use , and cumulative duration of use of metformin . All models accounted for latency and were adjusted for relevant potential confounding factors . Results : Overall , ever use of metformin was not associated with the incidence of colorectal cancer [ RR : 0.93 ; 95 % confidence interval ( CI ) , 0.73–1.18 ] . Similarly , no dose – response relationship was observed in terms of cumulative duration of use . Conclusions : The use of metformin was not associated with the incidence of colorectal cancer in patients with type II diabetes . Impact : The results of this study do not support the launch of metformin r and omized controlled trials for the chemoprevention of colorectal cancer . Cancer Epidemiol Biomarkers Prev ; 22(10 ) ; 1877–83 . © 2013 AACR OBJECTIVE Meta-analyses of epidemiologic studies have suggested that metformin may reduce cancer incidence , but r and omized controlled trials did not support this hypothesis . RESEARCH DESIGN AND METHODS A retrospective cohort study , Clinical Practice Research Data link , was design ed to investigate the association between use of metformin compared with other antidiabetes medications and cancer risk by emulating an intention-to-treat analysis as in a trial . A total of 95,820 participants with type 2 diabetes who started taking metformin and other oral antidiabetes medications within 12 months of their diagnosis ( initiators ) were followed up for first incident cancer diagnosis without regard to any subsequent changes in pharmacotherapy . Cox proportional hazards models were used to estimate multivariable-adjusted hazard ratios ( HR ) and 95 % CI . RESULTS A total of 51,484 individuals ( 54 % ) were metformin initiators and 18,264 ( 19 % ) were sulfonylurea initiators , and 3,805 first incident cancers were diagnosed during a median follow-up time of 5.1 years . Compared with initiators of sulfonylurea , initiators of metformin had a similar incidence of total cancer ( HR 0.96 ; 95 % CI 0.89–1.04 ) and colorectal ( HR 0.92 ; 95 % CI 0.76–1.13 ) , prostate ( HR 1.02 ; 95 % CI 0.83–1.25 ) , lung ( HR 0.85 ; 95 % CI 0.68–1.07 ) , or postmenopausal breast ( HR 1.03 ; 95 % CI 0.82–1.31 ) cancer or any other cancer . CONCLUSIONS In this large study , individuals with diabetes who used metformin  had a similar risk of developing cancer compared with those who used sulfonylureas OBJECTIVE To investigate the association between type 2 diabetes , glucose-lowering therapies ( monotherapy with either metformin , sulphonylurea or insulin ) and cancer risk in Taiwan . METHODS Using Taiwan 's National Health Research Institutes data base of 1,000,000 r and om subjects from 2000 - 2008 , we found 61777 patients with type 2 diabetes ( age ≥20 years ) and 677378 enrollees with no record of diabetes . RESULTS After adjusting for age and sex , we found patients with diabetes to have significantly higher risk of all cancers ( OR : 1.176 ; 95 % CI : 1.149 - 1.204 , P < 0.001 ) . Diabetic patients treated with insulin or sulfonylureas had significantly higher risk of all cancers , compared to those treated with metformin ( OR : 1.583 ; 95 % CI : 1.389 - 1.805 , P < 0.001 and OR : 1.784 ; 95 % CI : 1.406 - 2.262 , P < 0.001 ) . Metformin treatment was associated with a decreased risk of colon and liver cancer compared to sulphonylureas or insulin treatment . Sulfonylureas treatment was associated with an increased risk of breast and lung cancer compared to metformin therapy . CONCLUSIONS Taiwanese with type 2 diabetes are at a high risk of breast , prostate , colon , lung , liver and pancreatic cancer . Those treated with insulin or sulfonylureas monotherapy are more likely to develop colon and liver cancer than those treated with metformin 
    Output:
    
Our meta- analysis suggested that metformin therapy may be associated with a decreased risk of colorectal adenomas and colorectal cancer in type 2 diabetes mellitus patients