Effect of metformin on the incidence of head and neck cancer in diabetics

Therapeutic Potential of Anti-Diabetes Drugs and Anti-Dyslipidemia Drugs to Mitigate Head and Neck Cancer Risk in Metabolic Syndrome

BACKGROUND

Head and neck cancer (HNC) encompasses a heterogeneous group of malignancies originating in the oral cavity, pharynx, nasopharynx, larynx, paranasal sinuses, and salivary glands. Accumulating evidence indicates that metabolic syndrome (MetS) characterized by a constellation of conditions including central adiposity, hyperglycemia, dyslipidemia, hypertension, and insulin resistance, may significantly influence cancer pathogenesis and progression.

RESULTS

MetS has been epidemiologically linked to elevated risk for multiple malignancies through various metabolic mechanisms involving chronic systemic inflammation, insulin resistance, and dysregulated lipid metabolism. Especially in HNC, recent studies demonstrated that MetS and metabolic imbalance conditions may contribute to carcinogenesis, disease progression, and clinical outcomes, but the exact mechanisms behind the association between excess fat accumulation and HNC risk remain unclear. Considering previous studies, pharmacological agents targeting metabolic pathways, including biguanides (metformin), thiazolidinediones, sodium-glucose cotransporter-2 (SGLT-2) inhibitors, and HMG-CoA reductase inhibitors (statins) are being investigated for potential repurposing in cancer prevention and adjuvant therapy.

CONCLUSIONS

Here, we summarize the latest evidence on the relationship between MetS and HNC, highlighting the therapeutic potential of anti-diabetes drugs and anti-dyslipidemia drugs in ameliorating various pathological problems in HNC patients with MetS.

Prospective Pilot Study of Second Primary Tumor Prevention With Erlotinib and Celecoxib in Early-Stage Squamous Cell Carcinoma of the Head and Neck: Long-Term Follow-Up

BACKGROUND

Patients with early-stage head and neck squamous cell carcinoma (HNSCC) have an increased risk for secondary primary tumors (SPT) after definitive treatment. The aim of this pilot trial was to investigate the safety and efficacy of erlotinib and celecoxib in preventing SPTs.

METHODS

Ten patients with stage I/II HNSCC who completed definitive treatment received erlotinib with celecoxib for 6 months. Primary objectives were safety assessment and SPT-free survival after completion of erlotinib and celecoxib. Secondary objectives included assessing overall survival (OS) and progression-free survival (PFS).

RESULTS

With a median follow-up of 9 (1.7-15.3) years, the median time to SPT-free survival was not reached. The estimated SPT-free survival was 78.8% at 15 years. Two patients had local recurrence, but none of our subjects developed mucosal squamous cell carcinoma at any site.

CONCLUSION

All three doses of erlotinib and the fixed dose of celecoxib were well tolerated with excellent SPT-free survival with long-term follow-up.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT00400374.

Oncogenic HRAS Induces Metformin Resistance in Head and Neck Cancer by Promoting Glycolytic Metabolism

Metformin administration has recently emerged as a candidate strategy for the prevention of head and neck squamous cell carcinoma (HNSCC). However, the intricate relationship between genetic alterations in HNSCC and metformin sensitivity is still poorly understood, which prevents the stratification of patients, harboring oral premalignant lesions that may benefit from the chemopreventive activity of metformin. In this study, we investigate the impact of prevalent mutations in HNSCC on response to metformin. Notably, we found that the expression of oncogenic HRAS mutants confers resistance to metformin in isogenic HNSCC cell systems, and that HNSCC cells harboring endogenous HRAS mutations display limited sensitivity to metformin. Remarkably, we found that metformin fails to reduce activation of the mTOR pathway in HRAS oncogene-expressing HNSCC cells in vitro and in vivo, correlating with reduced tumor suppressive activity. Mechanistically, we found that this process depends on the ability of HRAS to enhance glycolytic metabolism, thereby suppressing the requirement for oxidative phosphorylation to maintain the cellular energetic balance. Overall, our study revealed that HNSCC cells with oncogenic HRAS mutations exhibit diminished metformin sensitivity, thus shedding light on a potential mechanism of treatment resistance. This finding may also help explain the limited clinical responses to metformin in cancers with RAS mutations. Ultimately, our study underscores the importance of understanding the impact of the genetic landscape in tailoring precision cancer-preventive approaches in the context of HNSCC and other cancers that are characterized by the presence of a defined premalignant state, and therefore, are amenable to cancer interception strategies. Prevention Relevance: Our findings highlight the challenges of using metformin for cancer prevention in RAS-mutant cancers, where elevated glycolysis may reduce drug efficacy. This underscores the need to explore metformin's potential in early, premalignant stages, before metabolic shifts render it less effective.

Chemoprevention of Head and Neck Cancer: A Review of Current Approaches and Future Perspectives

Head and neck squamous cell carcinoma (HNSCC) is a spectrum of heterogeneous malignancies. A variety of genetic, environmental, and lifestyle factors contribute to the development of HNSCC. Carcinogenesis is a multistep process in which cell proliferation-associated oncogenes and cell-cycle regulation-associated tumor suppressor genes are dysregulated, resulting in premalignant lesions. Immune evasion is a critical step in the progression of benign lesions to advanced cancer. This review discusses the advances that have been made in chemoprevention strategies for HNSCC. The rationale for the use of chemopreventive agents to inhibit head and neck cancer development is highlighted by the positive outcomes of several clinical trials. We discuss the potential of some of the commonly studied agents including vitamin A analogs, EGFR inhibitors, COX-2 inhibitors, metabolic modulators, and natural compounds such as green tea, as well as immunotherapy and photodynamic therapy to prevent HNSCC. Our review provides insight into the potential benefits of these agents and the gaps that remain to be addressed. The published results reaffirm the promise of chemoprevention in head and neck cancer and suggest that continued exploration is needed to overcome the limitations. Because the current focus on chemopreventive agents is limited, major efforts in precision oncology approaches and substantial increase in funding will promote research into chemoprevention, which will eventually decrease the incidence of HNSCC.

Metformin and risk of hematological cancers in patients with diabetes: a systematic review and meta-analysis

FUNDING

No external funding.

Diabetes can increase the prevalence of EBV infection and worsen the prognosis of nasopharyngeal carcinoma

Epstein‒Barr virus (EBV) infection is a primary oncogenic factor of nasopharyngeal carcinoma (NPC) that elicits epithelial-mesenchymal transition (EMT). Although diabetic patients are more susceptible to various infectious diseases, the pathological association with virus-related NPC has not yet been clarified. Herein, we evaluated the influence of diabetes on the clinicopathological changes of 70 patients with NPC. Disease-specific survival (DSS) modified by viral infection was also analysed. The proportion of NPC patients with diabetes was 32.9% (23/70 cases), and 91.3% (21/23 cases) were infected with EBV detected by EBER-I in situ hybridisation. NPC with diabetes showed an effect on EMT evaluated by immunostaining for E-cadherin and vimentin, which was correlated with HbA1c levels. Receiver operating characteristic (ROC) curve analysis determined a HbA1c level of 6.5% as the cut-off value for primary disease death at 2 years [area under the curve (AUC) 0.76; sensitivity 0.64; and specificity 0.81]. High HbA1c levels (≥6.5%) significantly increased the number of lymph node metastases in NPC compared to low HbA1c levels (<6.5%, p<0.01). Diabetic NPC patients had a significantly poorer prognosis than all non-diabetic patients (DSS, 72 months vs not reached, p<0.05). Diabetic EBV-positive NPC patients had a significantly poorer prognosis than non-diabetic EBV-positive patients (DSS, 35 months vs not reached, p<0.01). Multivariate analysis using the Cox proportional hazards model also suggested that HbA1c ≥6.5% was a significant factor in poor prognosis, with a hazard ratio of 6.84 (p<0.05). Collectively, our results revealed for the first time a high prevalence of EBV infection, poor prognosis and the importance of proper glycaemic control in diabetic NPC patients.

Preventive and Therapeutic Effect of Metformin in Head and Neck Cancer: A Concise Review

BACKGROUND

Head and neck cancer (HNC) is a complex affection. Nowadays, conventional treatments are associated with many side effects, reducing the patient's quality of life. Recent studies suggest that metformin, a first-line treatment for diabetes, could decrease cancer incidence and improve cancer-related survival rates.

METHODS

This systematic review summarizes important data from studies evaluating metformin's contribution to preventing and treating HNC.

RESULTS

The results suggest a protective effect of metformin in HNC. However, no consensus has been found on its therapeutic effects. Metformin seems to confer an improved cancer-related survival rate in a diabetic population, but compared to a non-diabetic population, the review could not identify any advantages. Nevertheless, no studies presented a negative impact.

CONCLUSION

In conclusion, the results of this systematic review suggest that HNC patients may benefit from metformin. Indeed, it would reduce the HNC incidence. However, more studies are required to evaluate the effect on cancer-related survival rates.

Chemoprevention of oral cancer: A review and future perspectives

BACKGROUND

Oral cancer causes significant morbidity and mortality. Chemoprevention utilizes medication or natural compounds to reverse oral premalignant lesions and to prevent second primary tumors.

METHODS

A comprehensive PubMed database and Cochrane Library search from 1980 to 2021 was performed using the keywords "leukoplakia," "oral premalignant lesion," and "chemoprevention."

RESULTS

Chemopreventive agents included retinoids, carotenoids, cyclooxygenase inhibitor, herbal extracts, bleomycin, tyrosine kinase inhibitors, metformin, and immune checkpoint inhibitors. Although some agents demonstrated effect in reducing premalignant lesions and preventing second primary tumors, the results among different studies were highly variable.

CONCLUSIONS

The results of different trials, albeit inconsistent, provided substantial information for future studies. In the era of personalized medicine, future studies will focus on identifying specific biomarkers and molecular profile to monitor and to prevent malignant transformation. Larger trials are warranted to validate the effect of chemopreventive agents.

Integrative analyses of biomarkers and pathways for metformin reversing cisplatin resistance in head and neck squamous cell carcinoma cells

OBJECTIVES

In this study, transcriptome sequencing were performed to elucidate the molecular mechanism by which metformin inhibits head and neck squamous cell carcinoma (HNSCC) cells progression and sensitizes HNSCC cells to chemotherapy. We aimed to propose a novel chemotherapeutic approach with high efficacy and few side effects and provide a new strategy for HNSCC treatment.

DESIGN

The effects of metformin on the biological behaviors of HNSCC cells were validated by CCK8 cell proliferation assays, would healing assays and flow cytometric apoptosis assays. The appropriate metformin concentrations for the experimental pretreatment of HNSCC cells were selected based on experimental results, and the treated cells were subjected to transcriptome sequencing. After bioinformatics analysis and intersection with a post-chemotherapy resistance dataset from the GEO database numbered GSE102787, the genes were identified and used to predict potential metformin targets after functional enrichment analysis.

RESULTS

Metformin significantly inhibited the proliferation and migration and induced the apoptosis of Cal27 and FaDu cells. A total of 284 genes that are potentially targeted by metformin during HNSCC cell sensitization were identified by bioinformatics, and ten hub genes with high connectivity were selected. In particular, Fen1 overexpression was associated with poor prognosis in HNSCC patients.

CONCLUSIONS

Our study demonstrates that Fen1 is overexpressed in HNSCC tissues compared with normal tissues and that Fen1 overexpression is a poor prognostic factor in HNSCC patients. Metformin enhances the ability of cisplatin to inhibit HNSCC progression. Further studies are needed to explore the therapeutic value of Fen1 in HNSCC.

Action Mechanism of Metformin and Its Application in Hematological Malignancy Treatments: A Review

Hematologic malignancies (HMs) mainly include acute and chronic leukemia, lymphoma, myeloma and other heterogeneous tumors that seriously threaten human life and health. The common effective treatments are radiotherapy, chemotherapy and hematopoietic stem cell transplantation (HSCT), which have limited options and are prone to tumor recurrence and (or) drug resistance. Metformin is the first-line drug for the treatment of type 2 diabetes (T2DM). Recently, studies identified the potential anti-cancer ability of metformin in both T2DM patients and patients that are non-diabetic. The latest epidemiological and preclinical studies suggested a potential benefit of metformin in the prevention and treatment of patients with HM. The mechanism may involve the activation of the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway by metformin as well as other AMPK-independent pathways to exert anti-cancer properties. In addition, combining current conventional anti-cancer drugs with metformin may improve the efficacy and reduce adverse drug reactions. Therefore, metformin can also be used as an adjuvant therapeutic agent for HM. This paper highlights the anti-hyperglycemic effects and potential anti-cancer effects of metformin, and also compiles the in vitro and clinical trials of metformin as an anti-cancer and chemosensitizing agent for the treatment of HM. The need for future research on the use of metformin in the treatment of HM is indicated.

CD8+ and FoxP3+ T-Cell Cellular Density and Spatial Distribution After Programmed Death-Ligand 1 Check Point Inhibition

OBJECTIVES

To analyze CD8+ and FoxP3+ T-cell cellular density (CD) and intercellular distances (ID) in head and neck squamous cell carcinoma (HNSCC) samples from a neoadjuvant trial of durvalumab +/- metformin.

METHODS

Paired pre- and post-treatment primary HNSCC tumor samples were stained for CD8+ and FoxP3+. Digital image analysis was used to determine estimated mean CD8+ and FoxP3+ CDs and CD8+-FoxP3+ IDs in the leading tumor edge (LTE) and tumor adjacent stroma (TAS) stratified by treatment arm, human papillomavirus (HPV) status, and pathologic treatment response. A subset of samples was characterized for T-cell related signatures using digital spatial genomic profiling.

RESULTS

Post-treatment analysis revealed a significant decrease in FoxP3+ CD and an increase in CD8+ CDs in the TAS between patients receiving durvalumab and metformin versus durvlaumab alone. Both treatment arms demonstrated significant post-treatment increases in ID. Although HPV+ and HPV- had similar immune cell CDs in the tumor microenvironment, HPV+ pre-treatment samples had 1.60 times greater ID compared with HPV- samples, trending toward significance (p = 0.05). At baseline, pathologic responders demonstrated a 1.16-fold greater CD8+ CDs in the LTE (p = 0.045) and 2.28-fold greater ID (p = 0.001) than non-responders. Digital spatial profiling revealed upregulation of FoxP3+ and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) in the TAS (p = 0.006, p = 0.026) in samples from pathologic responders.

CONCLUSIONS

Analysis of CD8+ and FoxP3+ detected population differences according to HPV status, pathologic response, and treatment. Greater CD8+-FoxP3+ ID was associated with pathologic response. CD8+ and FoxP3+ T-cell distributions may be predictive of response to immune checkpoint inhibition.

CLINICALTRIALS

gov (Identifier NCT03618654).

LEVEL OF EVIDENCE

Level 3 Laryngoscope, 2022.

Survival Benefit of Metformin as an Adjuvant Treatment for Head and Neck Cancer: A Systematic Review and Meta-Analysis

Background/Aims: The relationship between the efficacy of metformin and the prognosis of patients with head and neck cancer (HNC) was still unclear. This study aims to clarify the prognostic value of metformin treatment using meta-analysis.

Methods: Studies related to HNC prognosis and metformin were searched in Cochrane Library, Embase, LILACS, MEDLINE and PubMed databases. A meta-analysis was performed to evaluate the association between metformin therapy and the prognosis of HNC on overall survival (OS), disease-free survival (DFS) and disease-specific survival (DSS) and whether article quality, comorbidities, age, region or smoking had an influence on the prognosis of metformin treatment. Pooled hazard ratio (HR) and 95% confidence interval (CI) were analyzed to assess the effect.

Results: Eleven eligible studies involving 14,694 participants were included. Metformin increased the OS (HR = 0.87, 95% CI: 0.76–0.99), but failed on DFS (HR = 0.67, 95% CI: 0.40–1.09) or DSS (HR = 0.69, 95% CI: 0.41–1.14) in HNC patients. Subgroup analysis showed metformin was associated with improved OS (HR = 0.66, 95% CI: 0.49–0.88), DFS (HR = 0.49, 95% CI: 0.26–0.92) and DSS (HR = 0.38, 95% CI: 0.22–0.65) in studies with higher Newcastle-Ottawa Scale (NOS) scores. Subgroup analysis of age indicated that patients younger than 65 years (OS, HR = 0.67, 95% CI: 0.49–0.92) were more likely to benefit from metformin treatment. Subgroup analysis of comorbidities showed metformin significantly improved patient outcomes in studies without adjusted for comorbidities (OS, HR = 0.66, 95% CI: 0.51–0.85; DSS, HR = 0.38, 95% CI: 0.22–0.65), but not in studies that adjusted for comorbidities.

Conclusions: Metformin improved the prognosis of HNC patients as an adjuvant therapy, especially in those with higher NOS scores. Age and comorbidities of HNC patients influenced the therapeutic effect of metformin. Further well-conducted investigations are needed.

Metabolic disorders and the risk of head and neck cancer: a protocol for a systematic review and meta-analysis

INTRODUCTION

Head and neck cancer squamous cell carcinoma (HNSCC) is the sixth most common cancer internationally. Established risk factors include smoking, alcohol and presence of human papillomavirus (HPV). The incidence rate of new disease continues to rise, despite falls in alcohol consumption and a reduction in smoking, the rising rates are unlikely to be solely attributed to HPV status alone. Obesity and its associated conditions such as type 2 diabetes (T2D) are implicated in the risk and progression of a variety of cancers, but there is paucity of evidence regarding its role in HNSCC.

METHODS AND ANALYSIS

A systematic review of cohort studies, reporting a risk of incident HNSCC, will be included. A systematic search strategy has been developed, multiple databases will be searched from January 1966 to November 2021, including Cochrane Library, OVID SP versions of Medline and EMBASE. The primary outcome will be incident HNSCC based on exposures of T2D, obesity, dyslipidaemia and hypertension as defined by the WHO. A combined risk effect across studies will be calculated using meta-analysis, although depending on the heterogeneity in study design, exposure and outcome reporting this may not be possible.

ETHICS AND DISSEMINATION

No ethical approval is required for this systematic review. The review will be published in a relevant peer-review journal and findings will be presented at scientific meetings in both poster and oral presentation form.

PROSPERO REGISTRATION NUMBER DETAILS

This study has been registered with the International Prospective Register of Systematic Reviews (PROSPERO) with study registration number CRD42021250520. This protocol has been developed in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols guidance statement.

Metformin use and the risk of anal intraepithelial neoplasia in type II diabetic patients

AIM

Emerging evidence has suggested that metformin may be protective against the development of human-papillomavirus-related cancers. Anal intraepithelial neoplasia (AIN) is highly associated with human papillomavirus infection and a precancerous status of anal cancer. The aim of this study was to investigate the relationship between metformin usage and the development of AIN in a large national sample.

METHODOLOGY

The IBM MarketScan dataset was used to design a nested case-control study from 2010 to 2017. Patients aged 18-65 years with type 2 diabetes mellitus (DM) were evaluated, and cases of AIN were identified. Four controls were randomly selected in the risk set of each case by using incidence density sampling. The association between metformin usage and AIN was assessed using multivariate logistic regression modelling.

RESULTS

A total of 258 patients with type 2 DM were diagnosed with AIN during the study interval, and these were matched to 1032 control patients without a diagnosis of AIN. Patients who developed AIN had 38% lower odds of prior metformin use compared to those without a history of AIN (P < 0.01) and this finding remained robust after adjusting for age, sex, human immunodeficiency virus infection and DM complications (P = 0.02). Patients with AIN had 56% lower odds of long-term metformin use compared to control patients (P = 0.01).

CONCLUSIONS

An AIN diagnosis in patients with DM is associated with 56% lower likelihood of prior metformin use. This relationship suggests that metformin could potentially play a protective role against AIN. Prospective studies in non-diabetic patients are warranted to examine these findings further.

Inhibition of mTOR signaling and clinical activity of metformin in oral premalignant lesions

BACKGROUND

The aberrant activation of the PI3K/mTOR signaling circuitry is one of the most frequently dysregulated signaling events in head and neck squamous cell carcinoma (HNSCC). Here, we conducted a single-arm, open-label phase IIa clinical trial in individuals with oral premalignant lesions (OPLs) to explore the potential of metformin to target PI3K/mTOR signaling for HNSCC prevention.

METHODS

Individuals with OPLs, but who were otherwise healthy and without diabetes, underwent pretreatment and posttreatment clinical exam and biopsy. Participants received metformin for 12 weeks (week 1, 500 mg; week 2, 1000 mg; weeks 3–12, 2000 mg daily). Pretreatment and posttreatment biopsies, saliva, and blood were obtained for biomarker analysis, including IHC assessment of mTOR signaling and exome sequencing.

RESULTS

Twenty-three participants were evaluable for response. The clinical response rate (defined as a ≥50% reduction in lesion size) was 17%. Although lower than the proposed threshold for favorable clinical response, the histological response rate (improvement in histological grade) was 60%, including 17% complete responses and 43% partial responses. Logistic regression analysis revealed that when compared with never smokers, current and former smokers had statistically significantly increased histological responses (P = 0.016). Remarkably, a significant correlation existed between decreased mTOR activity (pS6 IHC staining) in the basal epithelial layers of OPLs and the histological (P = 0.04) and clinical (P = 0.01) responses.

CONCLUSION

To our knowledge this is the first phase II trial of metformin in individuals with OPLs, providing evidence that metformin administration results in encouraging histological responses and mTOR pathway modulation, thus supporting its further investigation as a chemopreventive agent.

TRIAL REGISTRATION

NCT02581137

FUNDING

NIH contract HHSN261201200031I, grants R01DE026644 and R01DE026870

Metformin generates profound alterations in systemic and tumor immunity with associated antitumor effects

BACKGROUND

Metformin is a commonly used antidiabetic medication which has demonstrated promise as an anticancer agent alone and in combination with conventional treatment regimens. There is increasing evidence that metformin can also generate immunomodulatory effects in solid tumors and is currently being investigated as an adjunct to immune checkpoint inhibitors (ICIs). We hypothesized that metformin would generate a shift in immunity unfavorable to tumor growth and tested this hypothesis in a preclinical model of head and neck cancer.

METHODS

Using a syngeneic mouse model of human papillomavirus-associated head and neck cancer (mEER/MTEC), we tested the impact of metformin on systemic and local immunity and tumor growth velocity. We compared the effects of acute and chronic treatment regimens on immunocyte presence and activation using a combination of flow cytometry and targeted transcriptomic analysis.

RESULTS

Acute metformin exposure generated measurable shifts in systemic myeloid and T-cell populations in non-tumor-bearing mice and decreased myeloid derived suppressor cell (MDSC) levels in tumor draining lymph nodes of tumor-bearing mice. Although metformin decreased regulatory T-cell (T-reg) and MDSC levels and increased CD8+ levels in murine tumors when combined with ICIs, acute metformin exposure was insufficient to generate substantial antitumor activity. Conversely, long-term metformin treatment significantly reduced tumor growth velocity, increased the CD8+/T-reg ratio, increased tumor infiltrating lymphocyte levels and upregulated component genes of the previously validated T-cell inflamed expression profile.

CONCLUSIONS

Metformin generates complex systemic and local immune effects which vary as a function of treatment duration. Combinatorial strategies with ICIs must take into account both the complexity and variability of these effects in order to generate maximal antitumor activity in future clinical trials.

Type 2 diabetes mellitus and risk of head and neck cancer subtypes: a systematic review and meta-analysis of observational studies

AIMS

The association between type 2 diabetes mellitus (T2DM) and risk of head and neck cancer (HNC) remains unclear. This study aims to perform a system review and meta-analysis to explore this relationship.

METHODS

PubMed, Web of Science, and Embase databases were searched for studies published up to July 31, 2020, regarding the association between T2DM and HNC risk. A random-effects model was utilized to calculate summary relative risks (RRs) with corresponding 95% confidence intervals (CIs).

RESULTS

Fourteen case-control studies and thirteen cohort studies were included in our analysis. We observed a weak association between T2DM and risk of HNC overall, but there was no statistical significance (RR, 1.04; 95% CI, 0.88-1.23; I² = 83.2%). Interestingly, there was a strong association in East Asia (RR, 1.46; 95% CI, 1.21-1.77; I² = 36.6%). For HNC subtypes, T2DM conferred a significantly elevated risk in oral cancer (RR, 1.22; 95% CI, 1.01-1.47; I² = 89.0%). However, in subgroup analyses of smoking, alcohol use, and body mass index (BMI)/obesity adjustments, the association between T2DM and oral cancer risk became insignificant. In addition, T2DM was not associated with a statistically elevated risk of pharyngeal cancer (RR, 1.18; 95% CI, 0.94-1.49; I² = 72.9%) and laryngeal cancer (RR, 1.03; 95% CI, 0.88-1.22; I² = 71.2%).

CONCLUSIONS

This meta-analysis indicates that T2DM is associated with an increased risk of HNC in East Asia. As for site-specific cancer types, the risk of oral cancer was significantly increased in T2DM patients, which appear to be mediated or confounded by smoking, alcohol use, or BMI/obesity.

The Evolving Epidemiology of Nasopharyngeal Carcinoma

BACKGROUND

The epidemiology of nasopharyngeal carcinoma (NPC) has long been a source of fascination due to the malignancy's striking geographic distribution, the involvement of the oncogenic Epstein-Barr virus (EBV), the unique association with intake of Chinese-style salt-preserved fish, and etiologic heterogeneity by histologic subtype.

METHODS

This review summarizes the current epidemiologic literature on NPC, highlighting recent results from our population-based case-control study in southern China.

RESULTS

Findings from our case-control study provide new insight into the epidemiology of NPC, including a diminished role of Chinese-style salt-preserved fish, a profound impact of EBV genetic sequence variation, modest positive associations with passive smoking and household air pollution, and possible effects of oral health and the oral microbiome. Recent findings from other studies include a protective association with infectious mononucleosis, suggesting a causal role of early EBV infection; familial risk conferred by shared genetic variation in the host antibody-mediated immune response to EBV infection; and an unclear association with occupational exposure to formaldehyde.

CONCLUSIONS

To shed further light on the interplay of environmental, genetic, and viral causes of NPC, large pooled studies must accumulate sufficient cases with detailed exposure data.

IMPACT

New epidemiologic findings have reshaped the causal model for NPC.

Metformin - its anti-cancer effects in hematologic malignancies

The main anti-diabetic effect of metformin mediated through stimulation of adenosine monophosphate (AMP)-activated protein kinase (AMPK) is the inhibition of hepatic gluconeogenesis and triggering glucose uptake in skeletal muscles. Additionally, some new pathways, besides the AMPK activation, were discovered, that can explain wide-range properties of metformin. All these properties are now attracting the attention of researchers in the fields other than diabetes and the drug has been reported to have anti-cancer, immunoregulatory and anti-aging effects. Among others, the beneficial effects of metformin in hematological disorders like leukemias, lymphomas, and multiple myeloma were reported. Despite a great progress in therapy, these diseases are still incurable in most cases. Thus, there is an urgent need to discover novel, less toxic and more effective drugs especially for older or chemotherapy-resistant patients. In this review article, the current findings on the anti-cancer effect of metformin together with underlying possible mechanisms in blood cancers are discussed. However. to evaluate precisely these promising effects of metformin, more studies are required, because many of the published results are preclinical.

Metformin and risk of cancer among patients with type 2 diabetes mellitus: A systematic review and meta-analysis

AIM

We carried out this meta-analysis on all published studies to estimate the overall cancer risk of the use of metformin in T2DM patients.

METHODS

We searched the PubMed, Embase and CNKI databases for all articles within a range of published years from 2007 to 2019 on the association between the use of metformin and cancer risk in T2DM patients. The odds ratio (OR) corresponding to the 95% confidence interval (95% CI) was used to assess the association using a random-effect meta-analysis.

RESULTS

Finally, 67 studies met the inclusion criteria for this study, with 10,695,875 T2DM patients and 145,108 cancer cases. Overall, For T2DM patients of ever vs. never metformin users, there was statistical evidence of significantly decreased cancer risk was found to be associated with ever metformin users (OR=0.70, 95% CI=0.65-0.76). Considering T2DM may be a specific and independent risk factor for various forms of cancer, due to its particular metabolic characteristics of glucose intolerance and hyperinsulinemia, we performed a comparison to estimate the effects of metformin on cancer risk with other anti-diabetes medications (ADMs), our results found significantly decreased cancer risk to be associated with the use of metformin (OR=0.80, 95% CI=0.73-0.87).

CONCLUSION

Our meta-analysis indicated that metformin may be a independent protective factor for cancer risk in T2DM patients.

Association of Diabetes with Oral Cancer- an Enigmatic Correlation

Introduction:

Association of diabetes mellitus (DM) with head and neck cancers (HNC) is still controversial. In some studies, diabetic patients had an increased risk of cancer at some HNC subsites like oral cancer, while in other studies this risk was decreased. So, the present study aims to evaluate the association of diabetes mellitus, oral cancer with and without metformin and the role of habits in association with DM and metformin in the etiology of oral cancer.

Materials and methods:

This study was undertaken in the Kamineni Institute of Dental Sciences in collaboration with MNJ Institute of Oncology and Regional Cancer Centre, Hyderabad. The study includes 2 main groups, they are 500 Oral cancer patients and Control group includes 500 age and gender-matched patients with habits without any oral precancerous lesion/conditions. Odds ratios (OR) and 95% confidence intervals (CI) were estimated using unconditional logistic regression.

Results:

Out of 1000 subjects inverse relation of DM with oral cancer was observed. On comparison between oral cancer, diabetes and habits in study group and control group, decreased risk was observed with smokers (OR: 1.131and 95%CI: 0.68 -1.86) and non-chewers (OR: 2.43 and 95% CI: 1.31 - 4.49) and non-alcoholics (OR: 1.78 and 95% C.I:1.18 - 2.68). Metformin use among diabetic participants was associated with a decreased risk of oral cancer (OR: 0.51 and 95% C.I: 0.33 - 0.77). A negative association was observed in smokers (OR: 0.19 and 95% C.I.: 0.078 - 0.459), non-chewers (OR: 0.24 and 95% C.I : 0.11- 0.53) and non-alcoholics (OR: 0.46 and 95% C.I. : 0.29 - 0.727).

Conclusion:

Thus the present population based study results suggest an inverse association of DM and oral cancer with metformin and negative association of habits with DM and Metformin in etiology of oral cancer.

Phase 1 dose-finding study of metformin in combination with concurrent cisplatin and radiotherapy in patients with locally advanced head and neck squamous cell cancer

BACKGROUND

The 5-year overall survival (OS) rate remains at 50% for patients with locally advanced head and neck squamous cell carcinoma (LAHNSCC), thereby underscoring the need for improved treatments. An antidiabetic agent, metformin, was found in retrospective studies to improve survival in patients with HNSCC. Therefore, the authors conducted a phase 1 dose escalation study combining metformin with chemoradiotherapy in patients with LAHNSCC.

METHODS

Nondiabetic patients with LAHNSCC were enrolled in the current study to receive escalating doses of metformin and CRT based on the modified toxicity probability interval design. Metformin cohort doses included 2000 mg, 2550 mg, and 3000 mg daily in divided doses in addition to cisplatin (at a dose of 100 mg/m² on days 1, 22, and 43) and standard radiotherapy (70 grays). Adverse events were categorized as per the National Cancer Institute Common Terminology Criteria for Adverse Events (version 4.03).

RESULTS

Twenty patients were enrolled, 2 of whom withdrew consent. The median age of the patients was 56 years and the majority were male (83%), were white (88%), had p16-positive disease (72%), and were tobacco users (61%). The median length of metformin exposure was 28.5 days. The most common grade ≥3 toxicities were nausea (11%), vomiting (11%), mucositis (6%), acute kidney injury (17%), anemia (6%), and leukopenia (11%). Dose-limiting toxicities included diarrhea and acute kidney injury. After a median follow-up of 19 months, the 2-year overall survival and progression-free survival rates were 90% and 84%, respectively. No hypoglycemia events or lactic acidosis were observed. Cisplatin administration did not appear to affect metformin pharmacokinetics. The maximum tolerated dose for metformin could not be determined given the limited number of patients who tolerated metformin during chemoradiotherapy.

CONCLUSIONS

To the authors' knowledge, the current study is the first phase 1 trial combining metformin with chemoradiotherapy. Rates of overall survival and progression-free survival were encouraging in this limited patient population, and warrant further investigation in a phase 2 trial.

Diabetes and its Potential Impact on Head and Neck Oncogenesis

In recent years, the incidence of diabetes mellitus and cancer has increased sharply; indeed, these have become the two most important diseases threatening health and survival. Head and neck (HN) tumors are the sixth most common malignancies in humans. Numerous studies have shown that there are many common risk factors for diabetes mellitus and HN squamous cell carcinoma, including advanced age, poor diet and lifestyle, and environmental factors. However, the mechanism linking the two diseases has not been identified. A number of studies have shown that diabetes affects the development, metastasis, and prognosis of HN cancer, potentially through the associated hyperglycemia, hyperinsulinemia and insulin resistance, or chronic inflammation. More recent studies show that metformin, the first-line drug for the treatment of type 2 diabetes, can significantly reduce the risk of HN tumor development and reduce mortality in diabetic patients. Here, we review recent progress in the study of the relationship between diabetes mellitus and HN carcinogenesis, and its potential mechanisms, in order to provide a scientific basis for the early diagnosis and effective treatment of these diseases.

Impact of metformin on disease control and survival in patients with head and neck cancer: a retrospective cohort study

Objective

A number of in vitro and clinical studies have suggested potential antineoplastic effects of metformin. The impact of this medication on outcomes in head and neck cancer is less clear. Our aim was to determine the effect of metformin on outcomes within our large cohort of head and neck cancer patients with Type II Diabetes (T2DM).

Study design

Retrospective cohort study.

Setting

Tertiary Cancer Centre.

Subjects and methods

A retrospective review of individuals with head and neck squamous carcinoma (HNSCC) and T2DM between January 2005 and December 2011 at Princess Margaret Cancer Centre was conducted. Medication history was obtained from surveys at initial presentation and electronic medical record review. Using Cox regression analyses, the association between metformin use and local, regional and distant failures was explored. Subgroup analyses were conducted for oral cavity, oropharynx and larynx.

Results

A total of 329 HNSCC patients with T2DM were identified, including 195 metformin users and 134 non-metformin users. Patients were well-matched in terms of clinical, pathologic, and treatment factors. No difference in local, regional, or distant failure was observed between diabetic metformin users and diabetic non-metformin users for the entire cohort or within subgroup analysis for subsite. No difference between the two groups was observed for overall survival, recurrence-free survival, and disease-specific survival at 5 years.

Conclusion

No association between metformin use and oncologic outcomes were observed in this large cohort of HNSCC patients. Multicenter, prospective studies may be needed to verify previous studies identifying a potential anti-neoplastic effect of this medication.

Metformin Inhibits Progression of Head and Neck Squamous Cell Carcinoma by Acting Directly on Carcinoma-Initiating Cells

Metformin may reduce the progression of head and neck squamous cell carcinoma (HNSCC); however, whether metformin acts by altering the host metabolism or targets cancer-initiating cells remains poorly understood. This gap in knowledge has prevented the stratification of patient populations who are most likely to benefit from metformin treatment. Here, we explored whether metformin acts directly on HNSCC cells to inhibit aberrant cell growth. To investigate the tumor cell autonomous effects of metformin, we engineered representative HPV- and HPV+ HNSCC cells harboring typical genetic alternations to express the yeast mitochondrial NADH dehydrogenase (NDI1) protein, which is insensitive to metformin. NDI1 expression rescued the inhibitory effects of metformin on mitochondrial complex I, abolished the ability of metformin to activate AMP-activated protein kinase, and inhibited mTOR signaling both in vitro and in vivo, and was sufficient to render metformin ineffective to prevent HNSCC tumor growth. This experimental system provided an opportunity to identify metformin-regulated transcriptional programs linked to cancer cell growth inhibition in the tumor microenvironment. Remarkably, computational analysis of the metformin-induced transcriptome revealed that metformin downregulated gene expression signatures associated with cancer stemness and epithelial-mesenchymal transition, concomitant with increased expression of squamous differentiation genes. These findings support that metformin may act directly on cancer-initiating cells to prevent their progression to HNSCC, which may inform the selection of patients at risk of developing HNSCC in future early-stage clinical trials. SIGNIFICANCE: Metformin's ability to directly target HNSCC-initiating cells instead of exerting cancer preventive activity based solely on its systemic effects may inform the selection of patients in future precision prevention trials.

Diabetes in the practice of otolaryngology

Diabetes mellitus is the most common endocrine disease, characterized by chronic hyperglycemia. The hyperglycemic milieu leads to endothelial injury in blood vessels of variant size, which results in microangiopathy and macroangiopathy (atherosclerosis). Consequential ischemia of nerves and hyperglycemia by itself lead to nerve degeneration and generalized neuropathy, affecting most often the sensory peripheral nerves and the autonomic nervous system. Auditory, vestibular and olfactory sensorium may be compromised by DM. People with DM have an increased susceptibility to infection, as a result of neutrophil dysfunction and impaired humoral immunity. Therefore DM predisposes to certain infectious diseases, such as fungal sinusitis or malignant otitis externa, which are rare in general population. Recovery from infections or from injuries may be compromised by coexisting DM. In this review we discuss complications of DM in the head and neck region. Otolaryngologists and general practitioners should be alert to specific conditions related to DM and be minded of the relevant complications and consequences.

Immune Modulation of Head and Neck Squamous Cell Carcinoma and the Tumor Microenvironment by Conventional Therapeutics

Head and neck squamous cell carcinoma (HNSCC) accounts for more than 600,000 cases and 380,000 deaths annually worldwide. Although human papillomavirus (HPV)-associated HNSCCs have better overall survival compared with HPV-negative HNSCC, loco-regional recurrence remains a significant cause of mortality and additional combinatorial strategies are needed to improve outcomes. The primary conventional therapies to treat HNSCC are surgery, radiation, and chemotherapies; however, multiple other targeted systemic options are used and being tested including cetuximab, bevacizumab, mTOR inhibitors, and metformin. In 2016, the first checkpoint blockade immunotherapy was approved for recurrent or metastatic HNSCC refractory to platinum-based chemotherapy. This immunotherapy approval confirmed the critical importance of the immune system and immunomodulation in HNSCC pathogenesis, response to treatment, and disease control. However, although immuno-oncology agents are rapidly expanding, the role that the immune system plays in the mechanism of action and clinical efficacy of standard conventional therapies is likely underappreciated. In this article, we focus on how conventional and targeted therapies may directly modulate the immune system and the tumor microenvironment to better understand the effects and combinatorial potential of these therapies in the context and era of immunotherapy.

Does metformin usage improve survival in head and neck squamous cell carcinoma? A population-based study

BACKGROUND

We sought to expand upon preliminary data suggesting that metformin confers a survival benefit to patients with head and neck squamous cell carcinoma (HNSCC).

METHODS

A large-scale retrospective cohort study of all patients in Ontario diagnosed with squamous cancer of the larynx, hypopharynx, and nasopharynx between Dec 1st 2007 to Dec 1st 2012 was undertaken. The Institute for Clinical and Evaluative Sciences was accessed to obtain patient demographic, treatment and outcome information. We included patients on metformin at the time of diagnosis. Kaplan Meier methods and Cox Regression models were used.

RESULTS

Patients taking metformin at the time of diagnosis had a higher comorbid status but were otherwise similar to patients without metformin usage. Using multivariate analysis, neither overall survival nor disease specific survival was improved in patients on metformin (OS: HR 1.123, p = .338; DSS: HR 1.048, p = .792).

CONCLUSIONS

No survival advantage was observed in patients with HNSCC taking metformin at the time of diagnosis.

Metformin Clinical Trial in HPV+ and HPV- Head and Neck Squamous Cell Carcinoma: Impact on Cancer Cell Apoptosis and Immune Infiltrate

Background: Metformin, an oral anti-hyperglycemic drug which inhibits mitochondrial complex I and oxidative phosphorylation has been reported to correlate with improved outcomes in head and neck squamous cell carcinoma (HNSCC) and other cancers. This effect is postulated to occur through disruption of tumor-driven metabolic and immune dysregulation in the tumor microenvironment (TME). We report new findings on the impact of metformin on the tumor and immune elements of the TME from a clinical trial of metformin in HNSCC.

Methods: Human papilloma virus—(HPV–) tobacco+ mucosal HNSCC samples (n = 12) were compared to HPV+ oropharyngeal squamous cell carcinoma (OPSCC) samples (n = 17) from patients enrolled in a clinical trial. Apoptosis in tumor samples pre- and post-treatment with metformin was compared by deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Metastatic lymph nodes with extra-capsular extension (ECE) in metformin-treated patients (n = 7) were compared to archival lymph node samples with ECE (n = 11) for differences in immune markers quantified by digital image analysis using co-localization and nuclear algorithms (PD-L1, FoxP3, CD163, CD8).

Results: HPV–, tobacco + HNSCC (mean Δ 13.7/high power field) specimens had a significantly higher increase in apoptosis compared to HPV+ OPSCC specimens (mean Δ 5.7/high power field) (p < 0.001). Analysis of the stroma at the invasive front in ECE nodal specimens from both HPV—HNSCC and HPV+ OPSCC metformin treated specimens showed increased CD8+ effector T cell infiltrate (mean 22.8%) compared to archival specimens (mean 10.7%) (p = 0.006). Similarly, metformin treated specimens showed an increased FoxP3+ regulatory T cell infiltrate (mean 9%) compared to non-treated archival specimens (mean 5%) (p = 0.019).

Conclusions: This study presents novel data demonstrating that metformin differentially impacts HNSCC subtypes with greater apoptosis in HPV—HNSCC compared to HPV+ OPSCC. Moreover, we present the first in vivo human evidence that metformin may also trigger increased CD8+ Teff and FoxP3+ Tregs in the TME, suggesting an immunomodulatory effect in HNSCC. Further research is necessary to assess the effect of metformin on the TME of HNSCC.

Metformin and blood cancers

Type 2 diabetes mellitus and cancer are correlated with changes in insulin signaling, a pathway that is frequently upregulated in neoplastic tissue but impaired in tissues that are classically targeted by insulin in type 2 diabetes mellitus. Many antidiabetes treatments, particularly metformin, enhance insulin signaling, but this pathway can be inhibited by specific cancer treatments. The modulation of cancer growth by metformin and of insulin sensitivity by anticancer drugs is so common that this phenomenon is being studied in hundreds of clinical trials on cancer. Many meta-analyses have consistently shown a moderate but direct effect of body mass index on the incidence of multiple myeloma and lymphoma and the elevated risk of leukemia in adults. Moreover, new epidemiological and preclinical studies indicate metformin as a therapeutic agent in patients with leukemia, lymphomas, and multiple myeloma. In this article, we review current findings on the anticancer activities of metformin and the underlying mechanisms from preclinical and ongoing studies in hematologic malignancies.

Hypertension in malignancy-an underappreciated problem

Hypertension is one of the most common comorbidities in cancer patients with malignancy, in particular, in the elderly. On the other hand, hypertension is a long-term consequence of antineoplastic treatment, including both chemotherapy and targeted agents. Several chemotherapeutics and targeted drugs may be responsible for development or worsening of the hypertension. The most common side effect of anti-VEGF (vascular endothelial growth factor) treatment is hypertension. However, pathogenesis of hypertension in patients receiving this therapy appears to be associated with multiple pathways and is not yet fully understood. Development of hypertension was associated with improved antitumor efficacy in patients treated with anti-antiangiogenic drugs in some but not in all studies. Drugs used commonly as adjuvants such as steroids, erythropoietin stimulating agents etc, may also cause rise in blood pressure or exacerbate preexisiting hypertension. Hypotensive therapy is crucial to manage hypertension during certain antineoplastic treatment. The choice and dose of antihypertensive drugs depend upon the presence of organ dysfunction, comorbidities, and/or adverse effects. In addition, severity of the hypertension and the urgency of blood pressure control should also be taken into consideration. As there are no specific guidelines on the hypertension treatment in cancer patients we should follow the available guidelines to obtain the best possible outcomes and pay the attention to the individualization of the therapy according to the actual situation.

Leveraging Genomics for Head and Neck Cancer Treatment

The genomic landscape of head and neck squamous cell carcinoma (HNSCC) has been recently elucidated. Key epigenetic and genetic characteristics of this cancer have been reported and substantiated in multiple data sets, including those distinctive to the growing subset of human papilloma virus (HPV)-associated tumors. This increased understanding of the molecular underpinnings of HNSCC has not resulted in new approaches to treatment. Three Food and Drug Administration-approved molecular targeting agents are currently available to treat recurrent/metastatic disease, but these have exhibited efficacy only in subsets of HNSCC patients, and thus surgery, chemotherapy, and/or radiation remain as standard approaches. The lack of predictive biomarkers to any therapy represents an obstacle to achieving the promise of precision medicine. This review aims to familiarize the reader with current insights into the HNSCC genomic landscape, discuss the currently approved and promising molecular targeting agents under exploration in laboratories and clinics, and consider precision medicine approaches to HNSCC.

Metformin Effects on Metabolic Coupling and Tumor Growth in Oral Cavity Squamous Cell Carcinoma Coinjection Xenografts

Objective Many aggressive head and neck cancers contain 2 metabolically coupled tumor compartments: a glycolytic stromal compartment with low caveolin-1 (CAV1) and high monocarboxylate transporter 4 (MCT4) expression and a highly proliferative carcinoma cell compartment with high MCT1. Metabolites are shuttled by MCTs from stroma to carcinoma to fuel tumor growth. We studied the effect of carcinoma-fibroblast coinjection and metformin administration on a mouse model of head and neck squamous cell carcinoma. Study Design Xenograft head and neck squamous cell carcinoma model. Setting Basic science laboratory. Subjects and Methods Oral cavity carcinoma cells were injected alone or as coinjection with human fibroblasts into nude mice to generate xenograft tumors. Tumors were excised and stained with immunohistochemistry for markers of metabolic coupling and apoptosis, including MCT1, MCT4, CAV1, and TUNEL assay (terminal deoxynucleotidyl transferase nick end labeling). Strength of staining was assessed by a pathologist or computer-assisted pathology software. Metformin was administered orally to mice to test effects on immunohistochemical markers in xenografts. Results Coinjection tumors were 2.8-fold larger ( P = .048) and had 1.4-fold stronger MCT1 staining ( P = .016) than tumors from homotypic carcinoma cell injection. Metformin decreased the size of coinjection xenograft tumors by 45% ( P = .025). Metformin reduced MCT1 staining by 28% ( P = .05) and increased carcinoma cell apoptosis 1.8-fold as marked by TUNEL assay ( P = .005). Metformin did not have a significant effect on tumor size when CAV1 knockdown fibroblasts were used in coinjection. Conclusion Coinjection with fibroblasts increases tumor growth and metabolic coupling in oral cavity cancer xenografts. Fibroblast CAV1 expression is required for metformin to disrupt metabolic coupling and decrease xenograft size.

Dysregulations in the PI3K pathway and targeted therapies for head and neck squamous cell carcinoma

The phosphoinositide 3-kinase (PI3K) signaling pathway is the most commonly mutated pathway in head and neck squamous cell carcinoma (HNSCC). There are several drugs targeting members of the PI3K signaling pathway in development for HNSCC. In this article, we review the genetic alterations reported in the pathway pertinent to HNSCC, various agents in development targeting various mediators of the pathway, results from clinical trials, and remaining challenges in the development of PI3K pathway inhibitors.

Metformin effects on head and neck squamous carcinoma microenvironment: Window of opportunity trial

OBJECTIVE

The tumor microenvironment frequently displays abnormal cellular metabolism, which contributes to aggressive behavior. Metformin inhibits mitochondrial oxidative phosphorylation, altering metabolism. Though the mechanism is unclear, epidemiologic studies show an association between metformin use and improved outcomes in head and neck squamous cell carcinoma (HNSCC). We sought to determine if metformin alters metabolism and apoptosis in HNSCC tumors.

STUDY DESIGN

Window of opportunity trial of metformin between diagnostic biopsy and resection. Participants were patients with newly diagnosed HNSCC. Fifty patients were enrolled, and 39 completed a full-treatment course. Metformin was titrated to standard diabetic dose (2,000 mg/day) for a course of 9 or more days prior to surgery.

METHODS

Immunohistochemistry (IHC) for the metabolic markers caveolin-1 (CAV1), B-galactosidase (GALB), and monocarboxylate transporter 4 (MCT4), as well as the Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) apoptosis assay and Ki-67 IHC, were performed in pre- and postmetformin specimens. Exploratory mass spectroscopy imaging (MSI) to assess lactate levels also was performed in three subjects.

RESULTS

Metformin was well tolerated. The average treatment course was 13.6 days. Posttreatment specimens showed a significant increase in stromal CAV1 (P < 0.001) and GALB (P < 0.005), as well as tumor cell apoptosis by TUNEL assay (P < 0.001). There was no significant change in stromal MCT4 expression or proliferation measured by Ki67. Lactate levels in carcinoma cells were increased 2.4-fold postmetformin (P < 0.05), as measured by MSI.

CONCLUSION

Metformin increases markers of reduced catabolism and increases senescence in stromal cells as well as carcinoma cell apoptosis. This study demonstrates that metformin modulates metabolism in the HNSCC microenvironment.

LEVEL OF EVIDENCE

4. Laryngoscope, 127:1808-1815, 2017.

Metformin and the incidence of viral associated cancers in patients with type 2 diabetes

Limited studies have associated metformin with a reduced risk of viral associated cancers, however these had a number of methodological shortcomings. This study investigated whether the use of metformin is associated with a reduced risk of viral associated cancers in patients with type 2 diabetes. A cohort of 137,754 patients newly-prescribed non-insulin antidiabetic drugs between January 1, 1988 and March 31, 2016 was identified from the UK Clinical Practice Research Datalink and followed until a first-ever diagnosis of a viral associated cancer, death from any cause, end of registration with the practice, or March 31, 2016. Time-varying use of metformin was compared with use of other antidiabetic drugs, with exposures lagged by one year for latency purposes. Time-dependent Cox proportional hazards models were used to estimate adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) of incident viral associated cancer with use of metformin overall, by cumulative duration of use and viral etiology. Overall, there were 424 viral associated cancers during 759,810 person-years of follow-up (crude rate of 5.6 per 10,000 person-years). Metformin was not associated with a decreased rate of viral associated cancer (HR: 0.93, 95% CI: 0.65-1.32). There was no evidence of a duration-response relationship in terms of cumulative duration of use (p trend = 0.69), including with use of metformin for more than 10 years (HR 1.02, 95% CI: 0.52-1.99), or by viral etiology. In this large population-based cohort study, the use of metformin was not associated with a reduced risk of viral associated cancer.

Metformin Prevents the Progression of Dysplastic Mucosa of the Head and Neck to Carcinoma in Nondiabetic Patients

OBJECTIVE

Metformin is an oral anti-hyperglycemic agent used to treat type 2 diabetes mellitus (DM). In vitro and animal models have shown that metformin can prevent the progression of oral lesions to carcinoma; however, there is conflicting data in the clinical literature regarding risk reduction for malignancy in head and neck cancer (HNC).

STUDY DESIGN

Case series.

METHODS

We present 3 cases in which adjuvant metformin therapy was used to treat recurrent and multifocal dysplastic lesions in previously treated nondiabetic HNC patients.

RESULTS

Patients included 1 with a history of oral cavity squamous cell carcinoma (SCC) and 2 with a history of laryngeal SCC. Follow-up time ranged between 3 and 33 months. All 3 patients showed complete or partial regression of the remaining mucosal lesions and did not require any additional surgeries.

CONCLUSION

We present 3 cases of nondiabetic HNC patients with field cancerization who showed a good response to adjuvant therapy with metformin. The nondiabetic population is not affected by confounding factors such as increased risk of malignancy and decreased overall survival that is itself associated with abnormal glucose metabolism and is therefore an excellent cohort in which to study the use of adjuvant metformin therapy in HNC patients.

Metformin may reduce oral cancer risk in patients with type 2 diabetes

BACKGROUND

Whether metformin use may affect the risk of oral cancer required further investigation.

METHODS

The reimbursement database of the National Health Insurance in Taiwan was used. Patients with type 2 diabetes mellitus at an onset age of 25-74 years during 1999-2005 and newly treated with either metformin (n = 288198, "ever users of metformin") or other antidiabetic drugs (n = 16263, "never users of metformin") were followed for at least 6 months for oral cancer until December 31, 2011. The treatment effect of metformin (for ever versus never users, and for tertiles of cumulative duration of therapy) was estimated by Cox regression adjusted for propensity score (PS) or incorporated with the inverse probability of treatment weighting (IPTW) using PS.

RESULTS

The respective numbers of incident oral cancer in ever users and never users were 1273 (0.44%) and 119 (0.73%), with respective incidences of 92.7 and 163.6 per 100,000 person-years. The overall hazard ratios (95% confidence intervals) suggested a significantly lower risk [0.584 (0.483-0.707) for PS-adjusted model, and 0.562 (0.465-0.678) for IPTW model]. In tertile analyses, the PS-adjusted hazard ratios (95% confidence intervals) for the first (<21.5 months), second (21.5-45.9 months) and third (>45.9 months) tertile of cumulative duration were 1.403 (1.152-1.708), 0.557 (0.453-0.684) and 0.152 (0.119-0.194), respectively; and were 1.244 (1.024-1.511), 0.526 (0.429-0.645) and 0.138 (0.108-0.176), respectively, for IPTW.

CONCLUSIONS

Metformin may significantly reduce the risk of oral cancer, especially when the cumulative duration is more than 21.5 months.

The Influence of Diabetes Mellitus and Metformin on Distant Metastases in Oropharyngeal Cancer: A Multicenter Study

PURPOSE

Local control in oropharyngeal cancer has improved to unprecedented rates with combined modality therapy; as a result, distant metastases are becoming a principal challenge. We aimed to determine the impact of diabetes mellitus and metformin use on clinical outcomes in a large population of oropharyngeal cancer patients treated in the modern era.

METHODS AND MATERIALS

We identified 1745 consecutive patients with oropharyngeal cancer treated at 2 large cancer centers with external beam radiation therapy from 1998 to 2011. A total of 184 patients had diabetes mellitus at the time of diagnosis, of whom 102 were taking metformin. The outcomes assessed included local failure-free survival (LFFS), regional failure-free survival (RFFS), distant metastasis-free survival (DMFS), and overall survival (OS).

RESULTS

The median follow-up time was 4.3 years. The 5-year actuarial rates of DMFS were 89.6% for nondiabetic patients and 78.7% for diabetic nonmetformin users (P=.011) and of OS were 83.0% for nondiabetic patients and 70.7% for diabetic nonmetformin users (P=.048). Diabetic metformin users had 5-year DMFS (90.1%) and OS (89.6%) similar to those of nondiabetic patients. Multivariate analysis (diabetic nonmetformin users as reference) demonstrated improved DMFS for nondiabetic patients (adjusted hazard ratio 0.54; 95% confidence interval 0.32-0.93; P=.03) and a trend toward improved DMFS with metformin use (adjusted hazard ratio 0.46; 95% confidence interval 0.20-1.04; P=.06). LFFS and RFFS were high in all groups and were not significantly different by diabetic status or metformin use.

CONCLUSIONS

Diabetic patients not using metformin independently have significantly higher rates of distant metastases than do nondiabetic patients, whereas metformin users have rates of distant metastases similar to those of nondiabetic patients. Further prospective investigation is warranted to validate the benefit of metformin in oropharyngeal cancer.

Prevention of tumor growth driven by PIK3CA and HPV oncogenes by targeting mTOR signaling with metformin in oral squamous carcinomas expressing OCT3

Most squamous cell carcinomas of the head and neck (HNSCC) exhibit a persistent activation of the PI3K-mTOR signaling pathway. We have recently shown that metformin, an oral antidiabetic drug that is also used to treat lipodystrophy in HIV-infected (HIV(+)) individuals, diminishes mTOR activity and prevents the progression of chemically induced experimental HNSCC premalignant lesions. Here, we explored the preclinical activity of metformin in HNSCCs harboring PIK3CA mutations and HPV oncogenes, both representing frequent HNSCC alterations, aimed at developing effective targeted preventive strategies. The biochemical and biologic effects of metformin were evaluated in representative HNSCC cells expressing mutated PIK3CA or HPV oncogenes (HPV(+)). The oral delivery of metformin was optimized to achieve clinical relevant blood levels. Molecular determinants of metformin sensitivity were also investigated, and their expression levels were examined in a large collection of HNSCC cases. We found that metformin inhibits mTOR signaling and tumor growth in HNSCC cells expressing mutated PIK3CA and HPV oncogenes, and that these activities require the expression of organic cation transporter 3 (OCT3/SLC22A3), a metformin uptake transporter. Coexpression of OCT3 and the mTOR pathway activation marker pS6 were observed in most HNSCC cases, including those arising in HIV(+) patients. Activation of the PI3K-mTOR pathway is a widespread event in HNSCC, including HPV(-) and HPV(+) lesions arising in HIV(+) patients, all of which coexpress OCT3. These observations may provide a rationale for the clinical evaluation of metformin to halt HNSCC development from precancerous lesions, including in HIV(+) individuals at risk of developing HPV(-) associated cancers.

Effects of metformin on head and neck cancer: a systematic review

Conventional therapeutic approaches for head and neck squamous cell carcinoma (HNSCC) are associated with many adverse effects that reduce quality of life. Therefore, identification of new less cytotoxic treatments is highly important. Metformin, which is commonly used for type 2 diabetes, may reduce cancer risk. A few clinical studies have examined the association between HNSCC and metformin. Therefore, the aim of this systematic review was to synthesize the available literature of the potential effect of metformin on HNSCC. This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist. Studies were gathered by searching PubMed, MEDLINE, EMBASE, LILACS, and the Cochrane database before June 28, 2014, with no time or language restrictions. Studies that evaluated individuals of any age that underwent metformin and had HNSCC and compared with patients without treatment or patients that use other kind of treatment for HNSCC (drugs or radiotherapy) were considered. Selected articles were evaluated according to the Critical Appraisal Skills Programs. Of 313 identified citations, 3 studies met the inclusion criteria and were used for qualitative analysis. These studies demonstrated that individuals taking metformin had decreased rates of locoregional recurrence and metastasis and improved overall survival and disease-free survival rates. Individuals taking metformin had a lower incidence of HNSCC than those not taking metformin. Though there are only a few studies on the topic, currently available evidence suggests an association between HNSCC and metformin use. Metformin reportedly improves the overall survival of HNSCC patients.