A cohort study of metformin exposure and survival in patients with stage I-III colorectal cancer

Association of metformin and statin uses with the prognosis of colon cancer: a meta-analysis

BACKGROUND

Metformin and statins are commonly used globally for the treatment of type 2 diabetes mellitus and dyslipidemia, respectively. Recently, multiple novel pathways have been discovered, which may contribute to the treatment of various types of cancer. Several meta-analysis studies have reported that the use of metformin or statins is associated with a lower risk of colon cancer compared to nonusers. In this study, our aim was to perform a meta-analysis and investigate the prognostic roles of these two medications in colon cancer.

METHODS

To identify relevant articles, literature searches were performed in the PubMed and Web of Science databases using a combination of keywords related to metformin, statins and colon cancer prognosis until August 2023. The study utilized STATA 12.0 software (Stata Corporation, College Station, Texas, USA) to compute all the hazard ratios (HRs) and 95% confidence intervals (CIs) regarding the association between metformin or statin uses and prognostic-related outcomes.

RESULTS

Our analysis revealed that the use of metformin was associated with a significantly lower overall mortality of colon cancer (HR = 0.63; 95% CI = 0.51-0.77; I2  = 94.9%; P  < 0.001), as well as lower cancer-specific mortality of colon cancer (HR = 0.68; 95% CI = 0.50-0.94; I2  = 91.9%; P  < 0.001). Similarly, the use of statins was also associated with a lower overall mortality of colon cancer (HR = 0.68; 95% CI = 0.60-0.78; I2  = 93.8%; P  < 0.001), as well as a lower cancer-specific mortality of colon cancer (HR = 0.74; 95% CI = 0.67-0.81; I2  = 82.2%; P  < 0.001).

CONCLUSION

Our meta-analysis study suggests that statins and metformin may have potential as adjuvant agents with significant benefits in the prognosis of colon cancer.

Prognostic role of metformin in diabetes mellitus type 2 patients with hepatocellular carcinoma: A systematic review and meta-analysis

BACKGROUND

Hepatocellular carcinoma (HCC) is among the commonest malignancies associated with significant cancer-related death. The identification of chemo-preventive agents following HCC treatments with the potential to lower the risk of HCC adverse course is intriguing. Metformin, a first-line agent used in the treatment of type 2 diabetes mellitus (T2DM), has been associated with inhibition of HCC growth.

AIM

To determine whether metformin can prevent adverse events (i.e., death, tumor progression, and recurrence) after any HCC treatment in T2DM patients.

METHODS

A systematic review of the published literature was undertaken focused on the role of metformin on outcomes in patients with T2DM and HCC receiving any tumor therapy. A search of the PubMed and Cochrane Central Register of Con-trolled Trials Databases was conducted.

RESULTS

A total of 13 studies (n = 14886 patients) were included in this review. With regard to the risk of death, a decreased risk was reported in cases receiving metformin, although this decrease was not statistically significant [odds ratio (OR) = 0.89, P = 0.42]. When only patients treated with curative strategies were considered, a more marked correlation between metformin and favorable cases was reported (OR = 0.70, P = 0.068). When analyzing palliative treatment, there was no statistical significance in terms of the correlation between metformin and favorable cases (OR = 0.74, P = 0.66). As for the risks of progressive disease and recurrence, no obvious correlation between metformin use and reduced risk was reported. When sub-analyses were performed for patients from different regions, the results for patients from Eastern countries showed a tendency for decreased risk of death in T2DM cases receiving metformin (OR = 0.69, P = 0.17), but the same was not seen in patients from Western countries (OR = 1.19, P = 0.31).

CONCLUSION

Metformin failed to show a marked impact in preventing adverse effects after HCC treatment. A trend was reported in T2DM cases receiving curative therapies in relation to the risk of death, especially in patients from Eastern regions. Great heterogeneity was reported among the different studies. Further large studies are required to definitively clarify the real impact of metformin as a chemopreventive agent for HCC.

Metformin Treatment Reduces CRC Aggressiveness in a Glucose-Independent Manner: An In Vitro and Ex Vivo Study

(1) Background: Metformin, an anti-diabetic drug, seems to protect against aggressive acquisition in colorectal cancers (CRCs). However, its mechanisms are still really unknown, raising questions about the possibility of its positive impact on non-diabetic patients with CRC. (2) Methods: An in vitro study based on human colon cancer cell lines and an ex vivo study with different colon cancer stages with proteomic and transcriptomic analyses were initiated. (3) Results: Metformin seems to protect from colon cancer invasive acquisition, irrespective of glucose concentration. (4) Conclusions: Metformin could be used as an adjuvant treatment to surgery for both diabetic and non-diabetic patients in order to prevent the acquisition of aggressiveness and, ultimately, recurrences.

Resistance to targeted therapy in metastatic colorectal cancer: Current status and new developments

Colorectal cancer (CRC) is one of the most lethal and common malignancies in the world. Chemotherapy has been the conventional treatment for metastatic CRC (mCRC) patients. However, the effects of chemotherapy have been unsatisfactory. With the advent of targeted therapy, the survival of patients with CRC have been prolonged. Over the past 20 years, targeted therapy for CRC has achieved substantial progress. However, targeted therapy has the same challenge of drug resistance as chemotherapy. Consequently, exploring the resistance mechanism and finding strategies to address the resistance to targeted therapy, along with searching for novel effective regimens, is a constant challenge in the mCRC treatment, and it is also a hot research topic. In this review, we focus on the current status on resistance to existing targeted therapies in mCRC and discuss future developments.

Prognostic value of metformin in cancers: An updated meta-analysis based on 80 cohort studies

BACKGROUND

Experiments have shown that metformin can inhibit cancer cell growth, but clinical observations have been inconsistent, so we pooled the currently available data to evaluate the impact of metformin on cancer survival and progression.

METHODS

PubMed, web of science, Embase, and Cochrane databases were searched. Pooled hazard ratios (HRs) were identified using a random-effects model to estimate the strength of the association between metformin and survival and progression in cancer patients.

RESULTS

We incorporated 80 articles published from all databases which satisfied the inclusion criterion. It showed that metformin was associated with better overall survival (hazard ratio [HR] = 0. 81; 95% confidence interval [CI]: [0.77-0.85]) and cancer-specific survival (HR = 0.79; 95% CI: [0.73-0.86]), and metformin was associated with progression-free survival (HR = 0.76; 95% CI: [0.66-0.87]). In patients with diabetes mellitus, the HR of overall survival was 0.79(95% CI: [0.75-0.83]), progression-free survival was 0.72(95% CI: [0.60-0.85]), and the cancer-specific survival was 0.76(95% CI: [0.68-0.86]). It was proposed that metformin can improve the prognosis of cancer patients with diabetes mellitus.

CONCLUSION

Based on cohort studies, metformin therapy has potential survival benefits for patients with malignancy, especially with the greatest benefits seen in breast cancer on overall survival, progression-free survival, and cancer-specific survival. And metformin also showed potential benefits in cancer-specific survival in colorectal and prostate cancer.

Efficacy of Metformin as Adjuvant Therapy in Metastatic Breast Cancer Treatment

Background: Metformin has been reported to have an anti-tumorigenic impact against metastatic breast cancer (MBC) cells through several mechanisms. Its effect can be evaluated by using many variables such as the response rate (RR) as well as the progression-free survival (PFS). Materials and methods: A prospective study was conducted to investigate and estimate the metformin effect on MBC. About 107 subjects were included in the study and were divided into two groups: Group A included non-diabetic MBC patients treated with metformin in conjunction with chemotherapy and group B included those treated with chemotherapy alone. Both PFS and RR were used as a criteria to evaluate the treatment outcome. Associated adverse effects of metformin were also assessed. Results: The average age of the participants in group A and group B was 50 vs. 47.5, respectively. No significant differences were detected between both cohorts concerning RR levels (regression disease (RD) 27.8% vs. 12.5%, stationary disease (SD) 44.4% vs. 41.7%, progression disease (PD) 27.8% vs. 45.8%, respectively, p = 0.074). Moreover, PFS showed no significant difference between both groups (p = 0.753). There was no significant correlation between metformin concentration and their adverse effects on the study participants. Conclusion: Metformin as an adjuvant therapy to MBC undergoing chemotherapy showed no significant survival benefit as determined by RR and PFS.

Antidiabetics, Anthelmintics, Statins, and Beta-Blockers as Co-Adjuvant Drugs in Cancer Therapy

Over the last years, repurposed agents have provided growing evidence of fast implementation in oncology treatment such as certain antimalarial, anthelmintic, antibiotics, anti-inflammatory, antihypertensive, antihyperlipidemic, antidiabetic agents. In this study, the four agents of choice were present in our patients’ daily treatment for nonmalignant-associated pathology and have known, light toxicity profiles. It is quite common for a given patient’s daily administration schedule to include two or three of these drugs for the duration of their treatment. We chose to review the latest literature concerning metformin, employed as a first-line treatment for type 2 diabetes; mebendazole, as an anthelmintic; atorvastatin, as a cholesterol-lowering drug; propranolol, used in cardiovascular diseases as a nonspecific inhibitor of beta-1 and beta-2 adrenergic receptors. At the same time, certain key action mechanisms make them feasible antitumor agents such as for mitochondrial ETC inhibition, activation of the enzyme adenosine monophosphate-activated protein kinase, amelioration of endogenous hyperinsulinemia, inhibition of selective tyrosine kinases (i.e., VEGFR2, TNIK, and BRAF), and mevalonate pathway inhibition. Despite the abundance of results from in vitro and in vivo studies, the only solid data from randomized clinical trials confirm metformin-related oncological benefits for only a small subset of nondiabetic patients with HER2-positive breast cancer and early-stage colorectal cancer. At the same time, clinical studies confirm metformin-related detrimental/lack of an effect for lung, breast, prostate cancer, and glioblastoma. For atorvastatin we see a clinical oncological benefit in patients and head and neck cancer, with a trend towards radioprotection of critical structures, thus supporting the role of atorvastatin as a promising agent for concomitant association with radiotherapy. Propranolol-related increased outcomes were seen in clinical studies in patients with melanoma, breast cancer, and sarcoma.

The effect of metformin on the survival of colorectal cancer patients with type 2 diabetes mellitus

Evidence from previous studies suggests a protective effect of metformin in patients with colorectal cancer (CRC). The aim of this study was to examine the associations between metformin use and overall survival (OS) and disease-free survival (DFS) in CRC patients with type 2 diabetes mellitus (DM). We retrospectively included patients who underwent surgery for CRC at Limoges’ University Hospital between 2005 and 2019 and diagnosed with type 2 DM. Data on the characteristics of patients, CRC, comorbidities and drug exposure were collected from the electronic medical records. The exposure was the use of metformin and the outcomes were OS and DFS. We identified 290 CRC patients with type 2 DM. A total of 144 (49.7%) of them were treated with metformin. Metformin users were significantly younger, with higher body mass index and less diabetes-related complications compared to non-users. The 2-year OS was significantly higher in metformin users than in non-users (86.9 ± 2.9% vs. 71.0 ± 4.0%, p = 0.001). In multivariate analysis, metformin use was associated with better OS (adjusted hazard ratios [aHR] = 0.45 95% confidence interval [95% CI]: 0.21–0.96) and better DFS (aHR = 0.31; 95% CI: 0.18–0.54). In conclusion, the use of metformin may improve OS and DFS in CRC patients with type 2 DM.

Effect of metformin use on the risk and prognosis of colorectal cancer in diabetes mellitus: a meta-analysis

BACKGROUND

Whether metformin is a protective factor of colorectal cancer (CRC) among CRC patients is still not entirely clear. Thus, we conducted this systemic review and meta-analysis to provide a comprehensive review of associations between metformin therapy and CRC risk or survival outcomes for clinical decisions.

METHODS

Articles published before July 2021 were searched in databases (PubMed and Web of Science). Odds ratio (OR)/risk ratio (RR) or hazard ratio (HR) and their confidence intervals (CIs) were computed using STATA 12.0 software. Q test and I2 were conducted to explore heterogeneities between studies.

RESULTS

The present meta-analysis showed that metformin use was associated with decreased risk and lower all-cause mortality of CRC in diabetes mellitus (DM) with random-effects models (risk: OR/RR = 0.71, 95% CI, 0.64-0.80, I2 = 89.3%, P < 0.001; all-cause mortality: HR = 0.72, 95% CI, 0.62-0.83, I2 = 60.1%, P = 0.014). In addition, the study showed that metformin use was associated with a lower CRC-specific mortality in DM in cohort studies with a fixed-effects model (HR = 0.80, 95% CI, 0.70-0.92, I2 = 34.7%, P = 0.190).

CONCLUSION

Overall, in this meta-analysis, we found that metformin may be a protective factor for CRC risk and prognosis in patients with DM. Further well-designed, large-scale clinical studies are needed to evaluate the accuracy of our findings and more preclinical experiments are needed to reveal the underlying mechanism of metformin.

Positive effect of metformin treatment in colorectal cancer patients with type 2 diabetes: national cohort study

We aimed to estimate colorectal cancer risk in patients with type 2 diabetes mellitus (T2DM) using metformin. Patients with colorectal cancer and diabetes from 2000 to 2012 were identified form Lithuanian Cancer Registry and the National Health Insurance Fund database. Standardized incidence ratios (SIRs) for colorectal cancers as a ratio of observed number of cancer cases in people with diabetes to the expected number of cancer cases in the underlying general population was calculated. We analysed 111 109 patients with diabetes. Overall, 1213 colorectal cancers were observed versus 954.91 expected within a period of observation entailing an SIR of 1.27 [95% confidence interval (CI): 1.20-1.34]. Significantly higher risk of colorectal cancer was found both in male and female patients with diabetes in all age groups. Higher risk was found for both colon and rectum cancers 1.36 (95% CI: 1.27-1.46) and 1.11 (95% CI: 1.01-1.22), respectively. There were no differences in risk over time since initial diabetes diagnosis. Never-users of metformin had twice higher risk of colorectal cancer compared to general population (SIR: 2.14, 95% CI: 1.95-2.35). Among metformin users, risk was lover (SIR: 1.47, 95% CI: 1.36-1.58) and colorectal cancer risk decreased with increasing cumulative dose of metformin (P < 0.001). Patients with T2DM had increased risk of colorectal cancer compared with the general Lithuanian population. Decreasing colorectal cancer risk with increasing cumulative dose of metformin indicates that metformin may be a protective agent for colorectal cancer development.

How far along are we in revealing the connection between metformin and colorectal cancer?

Colorectal cancer (CRC) is among the most prevalent cancers worldwide, and its prevention and reduction of incidence is imperative. The presence of diabetes has been associated with a 30% increased risk of CRC, likely through the mechanism of hyperinsulinemia, which promotes tumorigenesis via the insulin receptor in the epithelium or by insulin-like growth factor pathways, inflammation, or adipokines, inducing cancer cell proliferation and cancer spread. Metformin, the first-line agent in treating type 2 diabetes, has a chemopreventive role in CRC development. Additionally, preclinical studies suggest synergistic effects of metformin with oxaliplatin in inhibiting in vitro models of colon cancer. Although preclinical studies on the post diagnostic use of metformin were promising and suggested its synergistic effects with chemotherapy, the data on the possible effects of metformin after surgery and other CRC treatment in the clinical setting are less conclusive, and randomized controlled trials are still lacking.

Narrative review of the influence of diabetes mellitus and hyperglycemia on colorectal cancer risk and oncological outcomes

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Diabetes mellitus and hyperglycemia significantly affect the incidence and prognosis of colorectal cancer.

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Evidence of the effects of metformin remain controversial in cancer prognosis.

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Potential molecular mechanisms by which DM and hyperglycemia affects cancer risk.

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Potential roles of glucose modulation in CRC therapy.

Diabetes mellitus (DM) and hyperglycemia have been shown to have significant effects on the incidence, chemoresistance, and prognosis of colorectal cancer (CRC), as well as the outcomes of localized and metastatic CRC. Inflammation and endocrine effects may act as central mechanisms of DM and cancer and stimulate the insulin‐like growth factor 1–phosphoinositide 3-kinase–Akt–mammalian target of rapamycin (IGF-1–PI3K–AKT–mTOR) pathway. Dysregulation of the AMP-activated protein kinase (AMPK) pathway leads to metabolic imbalance and indicates cancer risk. The use of metformin for chemoprevention has been shown to reduce CRC and adenoma incidence through the upregulation of AMPK, which causes cell cycle arrest in the Gap 1–S (G1–S) phase and inhibits the mTOR pathway, even potentially reversing the epithelial–mesenchymal transition. However, evidence of the effects of metformin remain controversial in cancer prognosis. Several genes, such as transcription factor 7-like 2(TCF7L2), tumor protein P53 inducible nuclear protein 1(TP53INP1), gremlin 1 (GREM1), and potassium voltage-gated channel subfamily Q member 1(KCNQ1), are pleiotropically related to DM as well as cancer risk and prognosis. Epigenetic modification of members of the Let-7 family such as miR-497, miR-486, and miR-223 is strongly associated with impaired glucose tolerance and CRC risk. Herein we review the pathophysiological and epidemiological evidence as well as potential underlying molecular mechanisms by which DM and hyperglycemia affect CRC risk. We also suggest potential roles of glucose modulation in CRC therapy and propose an agenda for future research and clinical practice.

Anticancer potential of metformin: focusing on gastrointestinal cancers

Gastrointestinal cancers are one of the most common types of cancer that have high annual mortality; therefore, identification and introduction of safe drugs in the control and prevention of these cancers are of particular importance. Metformin, a lipophilic biguanide, is the most commonly prescribed agent for type 2 diabetes management. In addition to its great effects on lowering the blood glucose concentrations, the anti-cancer properties of this drug have been reported in many types of cancers such as gastrointestinal cancers. Hence the effects of this agent as a safe drug on the reduction of gastrointestinal cancer risk and suppression of these types of cancers have been studied in different clinical trials. Furthermore, the proposed mechanisms of metformin in preventing the growth of these cancers have been investigated in several studies. In this review, we discuss recent advances in elucidating the molecular mechanisms that are relevant for metformin use in gastrointestinal cancer treatment.

Role of Autophagy in Cancer Cell Response to Nucleolar and Endoplasmic Reticulum Stress

Eukaryotic cells are exposed to many internal and external stimuli that affect their fate. In particular, the exposure to some of these stimuli induces stress triggering a variety of stress responses aimed to re-establish cellular homeostasis. It is now established that the deregulation of stress response pathways plays a central role in cancer initiation and progression, allowing the adaptation of cells to an altered state in the new environment. Autophagy is a tightly regulated pathway which exerts “housekeeping” role in physiological processes. Recently, a growing amount of evidence highlighted the crucial role of autophagy in the regulation of integrated stress responses, including nucleolar and endoplasmic reticulum. In this review, we attempt to afford an overview of the complex role of nucleolar and endoplasmic reticulum stress-response mechanisms in the regulation of autophagy in cancer and cancer treatment.

Metformin and colorectal cancer: a systematic review, meta-analysis and meta-regression

PURPOSE

Metformin may have a role in reducing the incidence of colorectal cancer (CRC) and improving survival outcome. This meta-analysis explored the effect of metformin use on colorectal adenoma and cancer incidence, and colorectal oncological outcomes.

METHODS

A database search was conducted on Medline, Embase and CNKI for studies comparing metformin vs. non-metformin users, metformin users vs. non-diabetics and metformin users vs. diabetics with diet-only treatment. Meta-analysis was done with DerSimonian and Laird with risk ratios (RR), and hazard ratios (HR) for survival outcomes.

RESULTS

We included 58 studies and summarized incidences of colorectal adenoma and cancer, as well as cancer survival outcomes. Metformin users had a significant lower incidence of colorectal adenoma (RR 0.77, CI 0.67-0.88, p < 0.001), advanced adenoma (0.61, CI 0.42-0.88, p = 0.008) and CRC (RR 0.76, CI 0.69-0.84, p < 0.001) respectively compared with non-metformin users. Overall survival (HR 0.6, CI 0.53-0.67, p < 0.001) and CRC-specific survival (HR 0.66, CI 0.59-0.74, p < 0.001) were higher among metformin users compared with non-metformin users. Further analysis on overall survival of metastatic CRC patients revealed significantly higher survival rates in metformin users (HR 0.77, CI 0.68-0.87, p < 0.001).

CONCLUSION

This meta-analysis showed that metformin use significantly reduces colorectal adenoma and cancer incidence and improves colorectal cancer outcomes.

Metformin selectively inhibits metastatic colorectal cancer with the KRAS mutation by intracellular accumulation through silencing MATE1

CRC patients with KRAS mutations are confronted with limited targeted therapeutic options. In this study, we have shown that the median survival time for KRAS-mutation mCRC patients with diabetes on metformin is 37.8 mo longer than those treated with other hypoglycemic drugs in combination with standard systemic therapy. Metformin is preferentially accumulated in KRAS-mutation CRC cells in both primary cell cultures and patient-derived xenografts. The promising therapeutic activity of metformin has a negative correlation with MATE1 expression, which is proven to eliminate metformin from CRC cells. These findings indicate that KRAS-mutation mCRC patients could benefit from metformin treatment, and somatic KRAS status or MATE1 expression should be recommended to predict the therapeutic response of metformin in CRC.

Metastatic colorectal cancer (mCRC) patients have poor overall survival despite using irinotecan- or oxaliplatin-based chemotherapy combined with anti-EGFR (epidermal growth factor receptor) drugs, especially those with the oncogene mutation of KRAS. Metformin has been reported as a potentially novel antitumor agent in many experiments, but its therapeutic activity is discrepant and controversial so far. Inspiringly, the median survival time for KRAS-mutation mCRC patients with diabetes on metformin is 37.8 mo longer than those treated with other hypoglycemic drugs in combination with standard systemic therapy. In contrast, metformin could not improve the survival of mCRC patients with wild-type KRAS. Interestingly, metformin is preferentially accumulated in KRAS-mutation mCRC cells, but not wild-type ones, in both primary cell cultures and patient-derived xenografts, which is in agreement with its tremendous effect in KRAS-mutation mCRC. Mechanistically, the mutated KRAS oncoprotein hypermethylates and silences the expression of multidrug and toxic compound extrusion 1 (MATE1), a specific pump that expels metformin from the tumor cells by up-regulating DNA methyltransferase 1 (DNMT1). Our findings provide evidence that KRAS-mutation mCRC patients benefit from metformin treatment and targeting MATE1 may provide a strategy to improve the anticancer response of metformin.

Postdiagnostic metformin use and survival of patients with colorectal cancer: A Nationwide cohort study

Epidemiological evidence for the association between postdiagnostic metformin use and survival in patients with colorectal cancer (CRC) remains limited. Using the Taiwan Cancer Registry database, a cohort of 16,676 diabetic patients newly diagnosed with CRC from January 1, 2004 through December 31, 2014, followed until December 31, 2016, was identified. Postdiagnostic use of metformin (two or more prescriptions after CRC diagnosis) was defined as a time-dependent covariate with 6-month lag. Multivariate Cox regression model and stabilized inverse probability of treatment weighting (IPTW) were used to estimate adjusted effects of metformin on all-cause mortality and CRC-specific mortality during follow-up. A number of 11,438 (69%) received metformin after CRC diagnosis. Overall, 7,393 deaths, including 4,845 CRC-specific deaths, were observed during 64,322 person-years of follow-up. After adjustment for demographic and clinical covariates, metformin users had lower all-cause mortality than did nonusers (hazard ratio [HR], 0.42; 95% confidence interval [CI], 0.40-0.44) and lower CRC-specific mortality (HR, 0.41; 95% CI, 0.39-0.44). Similar but somewhat attenuated effects were observed after stabilized IPTW (HR for all-cause mortality, 0.56; 95% CI, 0.53-0.59; HR for CRC-specific mortality, 0.58; 95% CI, 0.55-0.61). Similar results were observed in stratified analyses of 2,112 patients with no prediagnostic metformin use and 14,564 patients with prediagnostic metformin use. Findings for both outcomes were consistent in multiple sensitivity analyses. Use of postdiagnostic metformin was associated with significantly lower all-cause mortality and CRC-specific mortality, regardless of prior metformin use. These findings support the use of metformin as an adjunct to standard care of diabetic patients with CRC.

The Effect of Metformin on Prognosis in Patients With Locally Advanced Gastric Cancer Associated With Type 2 Diabetes Mellitus

OBJECTIVES

This study examined the effect of metformin use on the prognosis of gastric cancer patients.

MATERIALS AND METHODS

The study population comprised 2187 patients who underwent curative gastrectomy for the treatment of gastric cancer. They were divided into 3 groups: metformin (n=103), non-metformin (n=139), and non-diabetes mellitus (DM) (n=1945) according to their history of type 2 DM and metformin use. Survival, disease recurrence, and the pathologic stage were analyzed.

RESULTS

Overall survival was better in the metformin group than in the non-DM group (P=0.005). Metformin use was an independent prognostic factor of overall survival, cancer recurrence, and peritoneal recurrence. An effect of metformin use was especially notable in patients with T4 or N0 disease.

CONCLUSIONS

Metformin improves the survival of patients with gastric cancer and type 2 DM.

For colorectal cancer patients with type II diabetes, could metformin improve the survival rate? A meta-analysis

OBJECTIVE

Current research is controversial about whether metformin can improve the survival rate of patients with colon cancer. Therefore, we conducted a meta-analysis to identify the association between metformin and the survival rate of colorectal cancer (CRC) patients with type II diabetes.

METHODS

We conducted a search in databases including Pubmed, EMBASE and Cochrane Library. All articles were published in the last decade, and the quality of each study was evaluated by the Newcastle-Ottawa Scale. Odds ratios (ORs) and its corresponding 95% confidence intervals (CIs) for each study were calculated and summary relative risk estimates with corresponding 95% CIs were generated using the random-effects model. Heterogeneity and publication bias were assessed.

RESULTS

Ten articles were included in this meta-analysis. The included articles were all cohort studies. In a pooled analysis of all studies, metformin using was associated with increased overall survival (OS) rate (OR, 0.54; 95% CI, 0.47 to 0.63) and cancer-specific survival (CS) rate (OR 0.59; 95% CI 0.43 to 0.82) of CRC patients with diabetes. We found that the effect of metformin is associated with geographical region through subgroup meta-analysis.

CONCLUSIONS

Metformin using was associated with an increased OS rate and CS rate of colorectal cancer.

Metformin Treatment for Diabetes Mellitus Correlates with Progression and Survival in Colorectal Carcinoma

BACKGROUND: Diabetes mellitus is unfavorably associated with cancer risk. The purpose of this multidisciplinary project was to evaluate a possible association of diabetes mellitus and other comorbidities and their treatment with progression of colorectal cancer. PATIENTS AND METHODS: We investigated the correlation between pathological characteristics and clinical course, including comorbidities in 1004 Czech patients diagnosed and surgically treated for colorectal adenocarcinoma (CRC) between 1999 and 2016. RESULTS: In our data set, CRC patients treated with metformin due to coexisting diabetes mellitus type 2 (T2DM) developed fewer distant metastases which clinically correlates with slower CRC progression. Survival in metformin subgroup was longer, particularly in men with CRC. Osteoporosis may be a negative factor of survival in CRC patients. CONCLUSIONS: Our findings also indicate that aging, higher tumor grade and TNM stage, coexistence of selected endocrine disorders, and metabolic abnormalities may change the tumor microenvironment and impact survival in colorectal cancer, although mechanism of these observations yet to be explained. Patients with diabetes mellitus type 2 treated with metformin may represent the altered microenvironment with specifically tuned metabolic molecular responses and with various epigenetic characteristics. More awareness and increased understanding of the mechanisms underlying the positive effect of metformin on patients' survival could offer insight into new treatment methods and permit more individualized treatment plans.

PCK1 and DHODH drive colorectal cancer liver metastatic colonization and hypoxic growth by promoting nucleotide synthesis

Colorectal cancer (CRC) is a major cause of human death. Mortality is primarily due to metastatic organ colonization, with the liver being the main organ affected. We modeled metastatic CRC (mCRC) liver colonization using patient-derived primary and metastatic tumor xenografts (PDX). Such PDX modeling predicted patient survival outcomes. In vivo selection of multiple PDXs for enhanced metastatic colonization capacity upregulated the gluconeogenic enzyme PCK1, which enhanced liver metastatic growth by driving pyrimidine nucleotide biosynthesis under hypoxia. Consistently, highly metastatic tumors upregulated multiple pyrimidine biosynthesis intermediary metabolites. Therapeutic inhibition of the pyrimidine biosynthetic enzyme DHODH with leflunomide substantially impaired CRC liver metastatic colonization and hypoxic growth. Our findings provide a potential mechanistic basis for the epidemiologic association of anti-gluconeogenic drugs with improved CRC metastasis outcomes, reveal the exploitation of a gluconeogenesis enzyme for pyrimidine biosynthesis under hypoxia, and implicate DHODH and PCK1 as metabolic therapeutic targets in CRC metastatic progression.

Metformin in colorectal cancer: molecular mechanism, preclinical and clinical aspects

Growing evidence showed the increased prevalence of cancer incidents, particularly colorectal cancer, among type 2 diabetic mellitus patients. Antidiabetic medications such as, insulin, sulfonylureas, dipeptyl peptidase (DPP) 4 inhibitors and glucose-dependent insulinotropic peptide (GLP-1) analogues increased the additional risk of different cancers to diabetic patients. Conversely, metformin has drawn attention among physicians and researchers since its use as antidiabetic drug exhibited beneficial effect in the prevention and treatment of cancer in diabetic patients as well as an independent anticancer drug. This review aims to provide the comprehensive information on the use of metformin at preclinical and clinical stages among colorectal cancer patients. We highlight the efficacy of metformin as an anti-proliferative, chemopreventive, apoptosis inducing agent, adjuvant, and radio-chemosensitizer in various colorectal cancer models. This multifarious effects of metformin is largely attributed to its capability in modulating upstream and downstream molecular targets involved in apoptosis, autophagy, cell cycle, oxidative stress, inflammation, metabolic homeostasis, and epigenetic regulation. Moreover, the review highlights metformin intake and colorectal cancer risk based on different clinical and epidemiologic results from different gender and specific population background among diabetic and non-diabetic patients. The improved understanding of metformin as a potential chemotherapeutic drug or as neo-adjuvant will provide better information for it to be used globally as an affordable, well-tolerated, and effective anticancer agent for colorectal cancer.

Suppressive effects of metformin on colorectal adenoma incidence and malignant progression

BACKGROUND

The linear progression from normal colonic epithelium to adenoma initiation, carcinoma transformation and metastasis is considered the classical model of colorectal cancer (CRC) development. Although metformin has been extensively reported to be negatively related to cancer incidence, the effect of metformin on CRC development remains unclear. We aimed to evaluate the role of metformin in the entire CRC linear progression.

METHODS

Systematic searches and data extraction were performed in the PubMed, Embase, and Cochrane Library databases on Jan 31, 2019. The combined relative ratios (RRs) of colorectal tumor incidence and the hazard ratios (HRs) of overall survival (OS) and cancer-specific survival (CSS) were evaluated by a random-effects model. Then, the effects of metformin were further assessed through stratified analyses by population, medication duration and dosage, dose-response analysis and comparison with other antidiabetic agents.

RESULTS

A total of 50 studies consisting of 238,540 cases of diabetes mellitus (DM) were included in this study. Metformin use was negatively associated with the incidence of colorectal adenoma (RR: 0.75, 95% CI: 0.65-0.86) and CRC (RR: 0.73, 95% CI: 0.58-0.90). Moreover, CRC patients benefited from metformin in terms of both OS (HR: 0.73, 95% Cl: 0.63-0.84) and CSS (HR: 0.60, 95% Cl: 0.50-0.73). Stratified analyses suggested that a long duration of high-dose metformin (RR: 0.52, 95% Cl: 0.36-0.83) was more effective than a short duration in Asian populations against colorectal adenoma (RR: 0.66, 95% Cl: 056-0.70) and CRC (RR: 0.45, 95% Cl: 0.29-0.70). Interestingly, metformin use decreased CRC risk in a dose-dependent manner (RR: 0.91, 95% CI: 0.87-0.95). In addition, the benefit of metformin on CRC was more significant than that of other antidiabetic agents, including insulin.

CONCLUSIONS

The use of metformin is associated with a lower incidence of adenoma and CRC and a better prognosis, especially in Asian populations.

Validation of the Survival Benefits of Metformin in Middle Eastern Patients With Type II Diabetes Mellitus and Colorectal Cancer

Purpose

Epidemiologic data from several populations suggest that metformin may decrease cancer risk and mortality in patients with colorectal cancer (CRC) and type II diabetes mellitus (DM). Although type II DM and CRC are major health problems in the Middle East, no investigations have been performed to test the effect metformin has on the outcome of patients with type II DM and CRC who are also treated with metformin.

Materials and Methods

We retrospectively reviewed the medical records of 1,902 patients diagnosed with CRC at King Hussein Cancer Center between January 2004 and December 2012, and identified 349 patients (18%) with type II DM; we censored the data of 28 patients because their antidiabetic medications were unknown. We then categorized these 321 patients into two groups: 192 patients treated with metformin (group A) and 129 patients treated with other antidiabetic medications (group B).

Results

Group A patients had significantly longer overall survival (89 months; 95% CI, 66 to 112 months) and progression-free survival (47 months; 95% CI, 15 to 79 months) than group B patients (overall survival: 36 months; 95% CI, 24 to 48 months; P ≤ .001; progression-free survival: 21 months; 95% CI, 13 to 29 months; P = .016). After adjustment for age, sex, body mass index, aspirin use, anticholesterol treatment, and CRC stage, group A patients had a 40% reduction in mortality (hazard ratio, 0.58; 95% CI, 0.4% to 0.85%; P = .005).

Conclusion

Our results support findings from other populations that patients with diabetes and CRC who are also treated with metformin have better outcomes than those treated with other antidiabetic medications.

Metformin increases cancer specific survival in colorectal cancer patients-National cohort study

PURPOSE

We aimed to assess oncological outcomes in colorectal cancer patients with type 2 diabetes mellitus (T2DM) using metformin.

METHODS

Patients with colorectal cancer and T2DM during 2000-2012 period were identified form Lithuanian Cancer Registry and the National Health Insurance Fund database. Colorectal cancer-specific survival (CS) was the primary outcome. It was measured from date of colorectal cancer diagnosis to date of death due to colorectal cancer, or last known date alive.

RESULTS

15,052 people who met eligibility criteria for this analysis, including 1094 (7.27%) with pre-existing type 2 diabetes (271 metformin never users and 823 metformin users) and 13 958 people without diabetes assessed. During follow-up (mean follow-up time was 4.4 years, with range from 1 day to 17 years) there were 10,927 deaths including 8559 from colorectal cancer. Significantly lower risk in CS between diabetic and non-diabetic people with lower risk of cancer-specific mortality (HR 0.87, 95% CI 0.80-0.94) in diabetic patient population was seen. After adjustment for age, stage at diagnosis and metformin usage, significant difference in colorectal CS between metformin users in diabetic patient population compared to non-diabetics and metformin non-users in diabetic patient population was found (0.80 (0.72-0.89) vs 1.00 and vs 1.05 (0.91-1.23)). Overall survival (OS) was better for diabetic patients with significant difference in diabetic metformin users (HR 0.91, 95% CI 0.79-0.94).

CONCLUSIONS

Colorectal cancer patients with T2DM treated with metformin as part of their diabetic therapy appear to have a superior OS and CS. However, prospective controlled studies are still needed to evaluate the efficacy of metformin as an anti-tumor agent.

The role of an anti-diabetic drug metformin in the treatment of endocrine tumors

Incidence of endocrine cancers is rising every year. Over the last decade, evidence has accumulated that demonstrates the anti-cancer effects of an anti-diabetic drug, metformin, in endocrine malignancies. We performed a literature review utilizing the PubMed, Medline and clinicaltrials.gov databases using the keyword 'metformin' plus the following terms: 'thyroid cancer', 'thyroid nodules', 'parathyroid', 'hyperparathyroidism', 'adrenal adenoma', 'Cushing syndrome', 'hyperaldosteronism', 'adrenocortical cancer', 'neuroendocrine tumor (NET)', 'pancreatic NET (pNET)', 'carcinoid', 'pituitary adenoma', 'pituitary neuroendocrine tumor (PitNET)', 'prolactinoma', 'pheochromocytoma/paraganglioma'. We found 37 studies describing the preclinical and clinical role of metformin in endocrine tumors. The available epidemiological data show an association between exposure of metformin and lower incidence of thyroid cancer and pNETs in diabetic patients. Metformin treatment has been associated with better response to cancer therapy in thyroid cancer and pNETs. Preclinical evidence suggests that the primary direct mechanisms of metformin action include inhibition of mitochondrial oxidative phosphorylation via inhibition of both mitochondrial complex I and mitochondrial glycerophosphate dehydrogenase, leading to metabolic stress. Decreased ATP production leads to an activation of a cellular energy sensor, AMPK, and subsequent downregulation of mTOR signaling pathway, which is associated with decreased cellular proliferation. We also describe several AMPK-independent mechanisms of metformin action, as well as the indirect mechanisms targeting insulin resistance. Overall, repositioning of metformin has emerged as a promising strategy for adjuvant therapy of endocrine tumors. The mechanisms of synergy between metformin and other anti-cancer agents need to be elucidated further to guide well-designed prospective trials on combination therapies in endocrine malignancies.

The beneficial effects of metformin on cancer prevention and therapy: a comprehensive review of recent advances

Metformin is a widely used drug in today’s prescriptions by physicians due to its specific effects in treating and curing type II diabetes. Diabetes is a common disease that may occur throughout human life, and can increase the likelihood of the occurrence of various types of cancer, such as colon, rectum, pancreas and liver cancers, compared to non-diabetic patients. Metformin inhibits mTOR activity by activating ATM (ataxia telangiectasia mutated) and LKB1 (liver kinase B1) and then adenosine monophosphate-activated kinase (AMPK), and thus prevents protein synthesis and cell growth. Metformin can activate p53 by activating AMPK and thereby ultimately stop the cell cycle. Given the potential of metformin in the treatment of cancer, it can be used in radiotherapy, chemotherapy and to improve the response to treatment in androgen derivatives (ADT), and also, according to available evidence, metformin can also be used to prevent various types of cancers. Generally, metformin can: 1) reduce the incidence of cancers, 2) reduce the mortality from cancers, 3) increase the response to treatment in cancer cells when using radiotherapy and chemotherapy, 4) optimize tumor movement and reduce the malignancy, 5) reduce the likelihood of relapse, and 6) reduce the damaging effects of ADT. Therefore, this drug can be used as a complementary therapeutic agent for cancer treatment and prevention. In this review, we have summarized the data from various experimental and clinical studies and highlight the possible potential effects of metformin on cancer therapeutic responses.

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Impact of Metformin Use and Diabetic Status During Adjuvant Fluoropyrimidine-Oxaliplatin Chemotherapy on the Outcome of Patients with Resected Colon Cancer: A TOSCA Study Subanalysis

BACKGROUND

Type 2 diabetes mellitus (T2DM) is associated with increased risk of colon cancer (CC), whereas metformin use seems to be protective. However, the impact of metformin use on the risk of death or disease recurrence after radical surgery for CC remains uncertain.

MATERIALS AND METHODS

This is a substudy conducted in patients with high-risk stage II or stage III CC randomized in the TOSCA trial, which compared 3 versus 6 months of fluoropyrimidine-oxaliplatin adjuvant chemotherapy. Objective of the study was to investigate the impact of metformin exposure during adjuvant chemotherapy on overall survival (OS) and relapse-free survival (RFS). We also evaluated the impact of T2DM or metformin dosage on clinical outcomes.

RESULTS

Out of 3,759 patients enrolled in the TOSCA trial, 133 patients with diabetes (9.2%) and 1,319 without diabetes (90.8%) were recruited in this study. After excluding 13 patients with diabetes without information on metformin exposure, 76 patients with T2DM (63.3%) were defined as metformin users and 44 (36.7%) as metformin nonusers. After a median follow-up of 60.4 months, 26 (21.7%) patients relapsed and 16 (13.3%) died. Metformin use was neither associated with OS (adjusted hazard ratio [HR], 1.51; 95% confidence interval [CI], 0.48-4.77; p = .4781) nor with RFS (HR, 1.56; 95% CI, 0.69-3.54; p = .2881). Similarly, we found no association between T2DM or metformin dosage and OS or RFS.

CONCLUSIONS

Metformin use and T2DM did not impact on OS or RFS in patients with resected CC treated with adjuvant fluoropyrimidine-oxaliplatin chemotherapy. Larger studies and longer follow-up are required to clarify the potential efficacy of metformin in improving the prognosis of patients with CC.

IMPLICATIONS FOR PRACTICE

The role of the antidiabetic drug metformin in colon cancer prevention and treatment is highly debated. While low-dose metformin reduced the incidence of colorectal adenomas in two prospective studies, its effect in patients with already established colon cancer remains unclear. In this study, the potential impact of metformin on the survival of resected colon cancer patients who received adjuvant chemotherapy was investigated in the context of the TOSCA study. We did not find any association between metformin use or dosages and patient survival. Prospective studies are required to draw definitive conclusions about metformin impact on colon cancer recurrence and survival.

Metformin-induced anticancer activities: recent insights

Metformin is a widely used antidiabetic drug, and there is evidence among diabetic patients that metformin is a chemopreventive agent against multiple cancers. There is also evidence in human studies that metformin is a cancer chemotherapeutic agent, and several clinical trials that use metformin alone or in combination with other drugs are ongoing. In vivo and in vitro cancer cell culture studies demonstrate that metformin induces both AMPK-dependent and AMPK-independent genes/pathways that result in inhibition of cancer cell growth and migration and induction of apoptosis. The effects of metformin in cancer cells resemble the patterns observed after treatment with drugs that downregulate specificity protein 1 (Sp1), Sp3 and Sp4 or by knockdown of Sp1, Sp3 and Sp4 by RNA interference. Studies in pancreatic cancer cells clearly demonstrate that metformin decreases expression of Sp1, Sp3, Sp4 and pro-oncogenic Sp-regulated genes, demonstrating that one of the underlying mechanisms of action of metformin as an anticancer agent involves targeting of Sp transcription factors. These observations are consistent with metformin-mediated effects on genes/pathways in many other tumor types.

Impact of type 2 diabetes mellitus on short-term and long-term outcomes of patients with esophageal squamous cell cancer undergoing resection: a propensity score analysis

Background

The association between type 2 diabetes mellitus (T2DM) and the risk of esophageal cancer remains unclear. The present study aimed to evaluate the impact of T2DM on short-term outcomes and long-term survival in patients with esophageal squamous cell cancer (ESCC).

Methods

The present retrospective study included 862 patients diagnosed with ESCC between January 2001 and December 2010. Among them, 280 patients had T2DM. A 1:1 propensity score-matched cohort consisting of 280 patients with and 280 without T2DM was selected from the 862 patients. The associations between T2DM and clinicopathologic characteristics were assessed using the χ² or Fisher’s exact test. Survival of ESCC patients with and without T2DM was calculated by using the Kaplan–Meier method and compared by using the Cox regression model between the two groups.

Results

The occurrence rate of anastomotic leakage was significantly higher in patients with T2DM than in those without T2DM (P < 0.001). In the subgroup with weight loss rate ≤ 5.05%, ESCC patients with T2DM had a significant longer overall survival than did those without T2DM (P = 0.003), whereas in the subgroup with weight loss rate > 5.05%, the patients without T2DM showed a longer survival (P = 0.001). Univariate and multivariate analysis results showed that T2DM was not an independent prognostic factor for patient survival.

Conclusions

Type 2 diabetes mellitus is not an independent prognostic factor in patients with ESCC. However, the combination of T2DM with severe weight loss would be a predictor of poor prognosis.

Association between metformin use after surgery for colorectal cancer and oncological outcomes: A nationwide register-based study

Colorectal cancer is one of the most common malignancies in the Western world, and even after surgical removal, there is a high recurrence rate. Metformin treatment has been associated with a reduced risk of developing cancer, but whether metformin influences the risk of recurrence is unknown. The aim of our study was to examine the association between treatment with metformin and recurrence-free, disease-free survival and all-cause mortality after surgery for colorectal cancer. The study was an observational register-based study and included 25,785 patients, of which 1,116 had medically treated diabetes and 966 started metformin treatment at some point postoperatively. Diabetes was not associated with neither disease-free (HR_adjusted  = 1.09, 95% CI 0.97-1.21, p = 0.15) nor recurrence-free survival (HR_adjusted  = 1.13, 95% CI 0.95-1.35, p = 0.17). The study found no difference in regards to disease-free or recurrence-free survival between the metformin treated group (HR_RFS  = 1.06, 95% CI 0.87-1.15, p = 0.57, HR_DFS  = 1.01, 95% CI 0.89-1.15, p = 0.85) and non-diabetic patients. Patients with diabetes had increased all-cause mortality (HR_adjusted  = 1.29, 95% CI 1.16-1.45, p < 0.0001). Metformin treatment did not affect all-cause mortality (HR = 1.07, 95% CI 0.94-1.22, p = 0.33) compared to non-diabetic patients. In conclusion, our study did not find an association between diabetes or metformin treatment and recurrence-free or disease-free survival after surgery for colorectal cancer. However, diagnosis of diabetes is associated with increased all-cause mortality.

Metformin use improves survival of diabetic liver cancer patients: systematic review and meta-analysis

Metformin has garnered considerable interest as a chemo-preventive and chemo-therapeutic agent given the increased risk of liver cancer among diabetic patients. This work was performed to illustrate the association between metformin use and survival of diabetic liver cancer patients. We conducted a comprehensive literature search of PubMed, Web of Science, Embase, BIOSIS Previews, Cochrane Library from inception to 12 May 2016. Meta-analyses were performed using Stata (version 12.0), with hazard ratios (HRs) and corresponding 95% confidence intervals (CIs) as effect measures. Eleven cohort studies involving 3452 liver cancer patients fulfilled the inclusion criteria. Meta-analyses showed that metformin use was associated with better survival (HR = 0.59; 95% CI, 0.42-0.83; p = 0.002) of liver cancer patients, and the beneficial effect persisted (HR = 0.64; 95% CI, 0.42-0.97; p = 0.035) when the population was restricted to diabetic liver cancer patients. After adjusting for age, etiology, index of tumor severity and treatment of liver cancer, the association between metformin use and better survival of liver cancer patients was stable, pooled HR ranged from 0.47 to 0.57. The results indicated that metformin use improved survival of diabetic liver cancer patients. However, the results should be interpreted with caution given the possibility of residual confounding. Further prospective studies are still needed to confirm the prognostic benefit of metformin use.

Interaction of smoking and metabolic syndrome in increasing the recurrence risk of colorectal cancer in a Chinese male cohort: a retrospective study

Whether smoking and metabolic syndrome (MetS) can affect colorectal carcinoma (CRC) prognosis remains debatable. Therefore, the present study aimed to examine the individual and combined effects of smoking and MetS on the prognosis of patients with localized CRC, including stage I to III disease. The relationship among smoking status, MetS, and CRC was assessed in 838 Chinese male patients. Cox proportional hazards regression analysis was used to evaluate CRC prognosis adjusted for clinicopathological variables. Relative excess risk of interaction (RERI), attributable proportion (AP), and synergy index (SI) were used to evaluate additive interactions between smoking and MetS. The presence of MetS was an independent risk factor for low rates of recurrence-free survival (RFS) but not for overall survival (OS). However, smoking was independently associated with both poor RFS and OS. Furthermore, the recurrence risk for current smokers with MetS was 1.62 times as high as the sum of risks in patients exposed to each risk factor alone. In conclusion, current smoking habit is a risk factor for both recurrence and cancer-specific mortality in CRC patients, while MetS is an independent predictor for CRC recurrence. Furthermore, these two factors have an additive effect on the recurrence risk of CRC.

Metformin transiently inhibits colorectal cancer cell proliferation as a result of either AMPK activation or increased ROS production

Metformin is a widely used and well-tolerated anti-diabetic drug that can reduce cancer risk and improve the prognosis of certain malignancies. However, the mechanism underlying its anti-cancer effect is still unclear. We studied the anti-cancer activity of metformin on colorectal cancer (CRC) by using the drug to treat HT29, HCT116 and HCT116 p53−/− CRC cells. Metformin reduced cell proliferation and migration by inducing cell cycle arrest in the G0/G1 phase. This was accompanied by a sharp decrease in the expression of c-Myc and down-regulation of IGF1R. The anti-proliferative action of metformin was mediated by two different mechanisms: AMPK activation and increase in the production of reactive oxygen species, which suppressed the mTOR pathway and its downstream targets S6 and 4EBP1. A reduction in CD44 and LGR5 expression suggested that the drug had an effect on tumour cells with stem characteristics. However, a colony formation assay showed that metformin slowed the cells’ ability to form colonies without arresting cell growth, as confirmed by absence of apoptosis, autophagy or senescence. Our finding that metformin only transiently arrests CRC cell growth suggests that efforts should be made to identify compounds that combined with the biguanide can act synergistically to induce cell death.

The Effect of Metformin on Mortality Among Diabetic Cancer Patients: A Systematic Review and Meta-analysis

BACKGROUND

Most data suggest that cancer patients with diabetes have worse outcomes, which may be reversed with metformin. Metformin might modulate the clinical outcomes of diabetic cancer patients. We performed a systematic review and meta-analysis based on published studies over the past five years to summarize the effects of metformin on diabetic cancer patients.

METHODS

We systematically searched for studies that were published over the past five years. Then, we evaluated these studies for inclusion and extracted the relevant data. The summary risk estimates for the association between metformin treatment and all-cause mortality (ACM) and cancer-specific mortality (CSM) were analyzed using random or fixed-effects models. Stratified analyses by cancer site and country were also conducted.

RESULTS

Based on the 42 studies included in our analysis (37 015 diabetic cancer patients), we found a significant benefit associated with metformin treatment on survival corresponding to 27% and 26% reductions in ACM (hazard ratio [HR] = 0.73, 95% confidence interval [CI] = 0.68 to 0.79, P < .001) and CSM (HR = 0.74, 95% CI = 0.64 to 0.86, P < .001), respectively. The ACM rates for colorectal cancer, endometrial cancer, breast cancer, prostate cancer, and ovarian cancer showed significant benefits associated with metformin treatment in our stratified analyses by cancer site. Stratified analyses by cancer site also showed a significant reduction in CSM for breast cancer. This association between metformin treatment and reduced CSM for diabetic breast cancer patients was also observed in our country subgroup analyses.

CONCLUSIONS

We found an association between metformin exposure and reduced ACM and CSM in diabetic patients with cancer. Our findings suggest that metformin treatment could be an effective treatment option for diabetic cancer patients.

The effect of metformin on survival of patients with pancreatic cancer: a meta-analysis

We conducted a meta-analysis to analyse the effect of metformin on survival of pancreatic cancer patients at various stages. We performed a systematic search of PubMed, Embase, Cochrane, and Web of Science to identify all relevant studies. Summary hazard ratios (HR) of survival and 95% confidence intervals (95% CI) were calculated with a fixed or random effects model according to inter-study heterogeneity. Nine retrospective cohort studies and two randomized controlled trials (RCTs) were eligible. There was a significant improvement in survival (HR = 0.86, 95% CI 0.76–0.97; P < 0.05) in the metformin group compared with control. Subgroup analysis indicated that metformin improved survival in patients with resection (HR = 0.79, 95% CI 0.69–0.91; P < 0.05) and patients with locally advanced tumors (HR = 0.68, 95% CI 0.55–0.84; P < 0.05) but not in patients with metastatic tumors, even when RCT data were included (HR = 0.99, 95% CI 0.70–1.40; P > 0.05), or were excluded (HR = 0.89, 95% CI 0.61–1.31; P > 0.05). This meta-analysis indicated that the effect of metformin does correlate with tumor stage but should be prudently considered given the limited and variable studies performed to data.

The association between metformin use and colorectal cancer survival among patients with diabetes mellitus: An updated meta-analysis

OBJECTIVE

Recent studies have reported conflicting results on the correlation between metformin use and outcomes in patients with colorectal cancer (CRC). A meta-analysis was performed to evaluate the efficacy of metformin therapy on the prognosis of CRC patients with type 2 diabetes mellitus (T2DM).

METHODS

We conducted a systematic search of PubMed, EMBASE, the Cochrane Library, and the Web of Science for related articles up to August 2016. Two investigators independently identified and extracted information. Pooled risk estimates [hazard ratios (HRs)] and 95% confidence intervals (CIs) were calculated using fixed-effects models. The risk of publication bias was assessed by examining funnel plot asymmetry as well as Egger's test and Begg's test.

RESULTS

Of 81 articles identified, 8 retrospective cohort studies, representing 6098 cases of CRC patients with T2DM who used metformin and 4954 cases of CRC patients with T2DM who did not use metformin, were included in this meta-analysis. There was no significant heterogeneity and quality difference between studies. Metformin users had significantly improved overall survival (OS) (HR = 0.82, 95% CI: 0.77-0.87, P = 0.000). However, Metformin use cannot affect CRC-specific survival (HR = 0.84, 95% CI: 0.69-1.02, P = 0.079) compared to non-users.

CONCLUSION

This meta-analysis suggests that metformin use may improve survival among CRC patients with T2DM. However, prospective controlled studies are still needed to rigorously evaluate the efficacy of metformin as an anti-tumor agent.

Epithelial-Mesenchymal Transition Phenotype, Metformin, and Survival for Colorectal Cancer Patients with Diabetes Mellitus II

OBJECTIVES

We aimed to explore the association between metformin treatment and epithelial-mesenchymal transition (EMT) phenotype and further appraise the prognostic values of metformin and EMT markers E-cadherin and vimentin for colorectal cancer (CRC) in clinical practice.

METHODS

We collected specimens and evaluated clinicopathological parameters of 102 stage I to III CRC patients with prediagnosed type 2 diabetes mellitus (DM II). Expression of E-cadherin and vimentin in tumors was detected by immunohistochemistry (IHC), and statistical analysis was performed using SPSS 19.0.

RESULTS

In correlation tests, we found a lower tumor cell EMT degree (more E-cadherin (P = 0.014) and less vimentin (P = 0.011) expression in patients who used metformin, and the expression of E-cadherin and vimentin was associated with serum CA19-9 (P = 0.048, P = 0.009), tumor invasive depth (T) (P < 0.001, P = 0.045), and lymph invasion (N) (P = 0.013, P = 0.001). In Cox multivariate regression analysis, E-cadherin was identified as a prognostic factor for disease-free survival (DFS) (P = 0.038) and metformin use (P = 0.015P = 0.044) and lymph invasion (P = 0.016P = 0.023) were considered as the prognostic factors for both DFS and overall survival (OS).

CONCLUSION

Our study suggested that metformin may impede the EMT process and improve survival for stage I-III CRC patients with DM II.

Metformin use and survival after non-small cell lung cancer: A cohort study in the US Military health system

Research suggests that metformin may be associated with improved survival in cancer patients with type II diabetes. This study assessed whether metformin use after non-small cell lung cancer (NSCLC) diagnosis is associated with overall survival among type II diabetic patients with NSCLC in the U.S. military health system (MHS). The study included 636 diabetic patients with histologically confirmed NSCLC diagnosed between 2002 and 2007, identified from the linked database from the Department of Defense's Central Cancer Registry (CCR) and the Military Health System Data Repository (MDR). Time-dependent multivariate Cox proportional hazards models were used to assess the association between metformin use and overall survival during follow-up. Among the 636 patients, 411 died during the follow-up. The median follow-up time was 14.6 months. Increased post-diagnosis cumulative use (per 1 year of use) conferred a significant reduction in mortality (adjusted hazard ratio (HR) = 0.76; 95% CI = 0.65-0.88). Further analysis by duration of use revealed that compared to non-users, the lowest risk reduction occurred among patients with the longest duration of use (i.e. use for more than 2 years) (HR = 0.19; 95% CI = 0.09-0.40). Finally, the reduced mortality was particularly observed only among patients who also used metformin before lung cancer diagnosis and among patients at early stage of diagnosis. Prolonged duration of metformin use in the study population was associated with improved survival, especially among early stage patients. Future research with a larger number of patients is warranted.

Metformin and breast cancer stage at diagnosis: a population-based study

PURPOSE

The objective of the present study was to use a large, population-based cohort to examine the association between metformin and breast cancer stage at diagnosis while accounting for mammography differences.

METHODS

We used data from Ontario administrative health databases to identify women 68 years of age or older with diabetes and invasive breast cancer diagnosed from 1 January 2007 to 31 December 2012. Adjusted logistic regression models were used to compare breast cancer stage at diagnosis (stages i and ii vs. iii and iv) between the women exposed and not exposed to metformin. We also examined the association between metformin use and estrogen receptor status, tumour size, and lymph node status in the subset of women for whom those data were available.

RESULTS

We identified 3125 women with diabetes and breast cancer; 1519 (48.6%) had been exposed to metformin before their cancer diagnosis. Median age at breast cancer diagnosis was 76 years (interquartile range: 72-82 years), and mean duration of diabetes was 8.8 ± 5.9 years. In multivariable analyses, metformin exposure was not associated with an earlier stage of breast cancer (odds ratio: 0.98; 95% confidence interval: 0.81 to 1.19). In secondary analyses, metformin exposure was not associated with estrogen receptor-positive breast cancer, tumours larger than 2 cm, or positive lymph nodes.

CONCLUSIONS

This population-based study did not show an association between metformin use and breast cancer stage or tumour characteristics at diagnosis. Our study considered older women with long-standing diabetes, and therefore further studies in younger patients could be warranted.

Prognostic role of metformin intake in diabetic patients with colorectal cancer: An updated qualitative evidence of cohort studies

Several observational studies have shown that metformin can modify the risk and survival of colorectal cancer (CRC) in patients with diabetes mellitus, although the magnitude of this relationship has not been determined. We conducted an updated systematic review and meta-analysis to analyze the association between metformin and CRC mortality and searched relevant databases up to July 2016. The primary outcome was overall survival (OS). Secondary outcomes were cancer-specific survival (CS) and disease-free survival (DFS). Summary hazard ratios (HRs) were calculated using a random-effects model. Seventeen studies enrolling 269,417 participants were eligible for inclusion. Comparing with non-metformin users in diabetic CRC patients, the summary HRs for OS in metformin users were 0.69 (95% CI, 0.61-0.77). Subgroup analyses stratified by the study characteristics and sensitivity analysis by the trim-and-fill method (adjusted HR 0.77, 95% CI, 0.67-0.87) confirmed the robustness of the results. However, significant OS benefit was noted in patients with stage II and III disease. Five studies reported the CRC prognosis for CS and three for DFS; metformin intake was significantly associated with patient CS (HR 0.75, 95% CI, 0.59-0.94), but not DFS (HR 0.38, 95% CI, 0.13-1.17). Our findings suggest that metformin intake is associated with improved survival outcomes in terms of OS and CS in CRC patients with diabetes, particular for OS in stage II and stage III patients. Further studies should be conducted to determine CRC survival between metformin use and patient specific clinical and molecular profiles.

Metformin Improves Overall Survival of Colorectal Cancer Patients with Diabetes: A Meta-Analysis

Introduction. Diabetic population has a higher risk of colorectal cancer (CRC) incidence and mortality than nondiabetics. The role of metformin in CRC prognosis is still controversial. The meta-analysis aims to investigate whether metformin improves the survival of diabetic CRC patients. Methods. PubMed, EMBASE, and Cochrane Library were searched till July 1, 2016. Cohort studies were included. All articles were evaluated by Newcastle-Ottawa Scale. Hazard Ratios (HRs) with 95% confidence intervals (CIs) for each study were calculated and pooled HRs with corresponding 95% CIs were generated using the random-effects model. Heterogeneity and publication bias were assessed. Results. We included seven cohort studies with a medium heterogeneity (I² = 56.1% and p = 0.033) in our meta-analysis. An improved overall survival (OS) for metformin users over nonusers among colorectal cancers with diabetes was noted (HR 0.75; 95% CI 0.65 to 0.87). However, metformin reveals no benefits for cancer-specific survival (HR 0.79, 95%, CI 0.58 to 1.08). Conclusions. Metformin prolongs the OS of diabetic CRC patients, but it does not affect the CRC-specific survival. Metformin may be a good choice in treating CRC patients with diabetes mellitus in clinical settings.

Metformin as an adjuvant treatment for cancer: a systematic review and meta-analysis

BACKGROUND

Metformin use has been associated with a reduced risk of developing cancer and an improvement in overall cancer survival rates in meta-analyses, but, to date, evidence to support the use of metformin as an adjuvant therapy in individual cancer types has not been presented.

PATIENTS AND METHODS

We systematically searched research databases, conference abstracts and trial registries for any studies reporting cancer outcomes for individual tumour types in metformin users compared with non-users, and extracted data on patients with early-stage cancer. Studies were assessed for design and quality, and a meta-analysis was conducted to quantify the adjuvant effect of metformin on recurrence-free survival (RFS), overall survival (OS) and cancer-specific survival (CSS), to inform future trial design.

RESULTS

Of 7670 articles screened, 27 eligible studies were identified comprising 24 178 participants, all enrolled in observational studies. In those with early-stage colorectal cancer, metformin use was associated with a significant benefit in all outcomes [RFS hazard ratio (HR) 0.63, 95% confidence interval (CI) 0.47-0.85; OS HR 0.69, CI 0.58-0.83; CSS HR 0.58, CI 0.39-0.86]. For men with early-stage prostate cancer, metformin was associated with significant, or borderline significant, benefits in all outcomes (RFS HR 0.83, CI 0.69-1.00; OS HR 0.82, CI 0.73-0.93; CSS HR 0.58, CI 0.37-0.93); however, there was significant heterogeneity between studies. The data suggest that prostate cancer patients treated with radical radiotherapy may benefit more from metformin (RFS HR 0.45, CI 0.29-0.70). In breast and urothelial cancer, no significant benefits were identified. Sufficient data were not available to conduct analyses on the impact of metformin dose and duration.

CONCLUSIONS

Our findings suggest that metformin could be a useful adjuvant agent, with the greatest benefits seen in colorectal and prostate cancer, particularly in those receiving radical radiotherapy, and randomised, controlled trials which investigate dose and duration, alongside efficacy, are advocated.

Relationship Between Metformin Use and Recurrence and Survival in Patients With Resected Stage III Colon Cancer Receiving Adjuvant Chemotherapy: Results From North Central Cancer Treatment Group N0147 (Alliance)

BACKGROUND

Preclinical and epidemiological data suggest that metformin might have antineoplastic properties against colon cancer (CC). However, the effect of metformin use on patient survival in stage III CC after curative resection is unknown. The survival outcomes were comparable regardless of the duration of metformin use.

PATIENTS AND METHODS

Before randomization to FOLFOX (folinic acid, 5-fluorouracil, oxaliplatin) with or without cetuximab, 1,958 patients with stage III CC enrolled in the N0147 study completed a questionnaire with information on diabetes mellitus (DM) and metformin use. Cox models were used to assess the association between metformin use and disease-free survival (DFS), overall survival (OS), and the time to recurrence (TTR), adjusting for clinical and/or pathological factors.

RESULTS

Of the 1,958 patients, 1,691 (86%) reported no history of DM, 115 reported DM with metformin use (6%), and 152 reported DM without metformin use (8%). The adjuvant treatment arms were pooled, because metformin use showed homogeneous effects on outcomes across the two arms. Among the patients with DM (n = 267), DFS (adjusted hazard ratio [aHR], 0.90; 95% confidence interval [CI], 0.59-1.35; p = .60), OS (aHR, 0.99; 95% CI, 0.65-1.49; p = .95), and TTR (aHR, 0.87; 95% CI, 0.56-1.35; p = .53) were not different for the metformin users compared with the nonusers after adjusting for tumor and patient factors. The survival outcomes were comparable regardless of the duration of metformin use (<1, 1-5, 6-10, ≥11 years) before randomization (p_trend = .64 for DFS, p_trend = .84 for OS, and p_trend = .87 for TTR). No interaction effects were observed between metformin use and KRAS, BRAF mutation status, tumor site, T/N stage, gender, or age.

CONCLUSIONS

Patients with stage III CC undergoing adjuvant chemotherapy who used metformin before the diagnosis of CC experienced DFS, OS, and TTR similar to those for non-DM patients and DM patients without metformin use.

IMPLICATIONS FOR PRACTICE

The present study did not find any relationship between metformin use or its duration and disease-free survival, time to recurrence, and overall survival in a large cohort of patients with resected stage III colon cancer receiving adjuvant FOLFOX (folinic acid, fluorouracil, oxaliplatin)-based chemotherapy. This relationship was not modified by KRAS or BRAF mutation or DNA mismatch repair status. Metformin use did not increase or decrease the likelihood of chemotherapy-related grade 3 or higher adverse events.

Metformin, Diabetes, and Survival among U.S. Veterans with Colorectal Cancer

BACKGROUND

Metformin has been associated with improved colorectal cancer survival, but investigations are limited by small numbers of patients and confounding by diabetic severity. We examined the association between metformin use and overall survival (OS) in patients with diabetes and colorectal cancer in a large population of U.S. veterans, while adjusting for measures of diabetic severity.

METHODS

Patients diagnosed with colorectal cancer from January 2001 to December 2008 were identified from the Veterans Affairs Central Cancer Registry. Multivariable models were used to examine the adjusted association of OS with diabetes and use of antidiabetic medications.

RESULTS

There were 21,352 patients diagnosed with colorectal cancer identified (n = 16,355 nondiabetic patients, n = 2,038 diabetic patients on metformin, n = 2,136 diabetic patients on medications other than metformin, n = 823 diabetic patients not on antidiabetic medication). Diabetic patients had a significantly worse OS than nondiabetic patients, but metformin users had only a 10% increase in death (HR_adj 1.10; 95% CI, 1.03-1.17, P = 0.004), as compared with 22% for users of other antidiabetic medications (HR_adj 1.22; 95% CI, 1.15-1.29, P < 0.0001). Among colorectal cancer patients with diabetes, metformin users had a 13% improved OS versus patients taking other antidiabetic medications (HR_adj 0.87; 95% CI, 0.79-0.95, P = 0.003), while diabetic patients not on any antidiabetic medications did not differ with respect to OS (HR_adj 1.02; 95% CI, 0.90-1.15, P = 0.76).

CONCLUSIONS

Among diabetics with colorectal cancer, metformin use is associated with improved survival, despite adjustments for diabetes severity and other risk factors.

IMPACT

These data lend further support to the conduct of randomized studies of possible anticancer effects of metformin among patients with colorectal cancer. Cancer Epidemiol Biomarkers Prev; 25(10); 1418-25. ©2016 AACR.