Metformin and pancreatic cancer survival: Real effect or immortal time bias?

Competing risks analysis of external versus internal radiation in patients with hepatocellular carcinoma after controlling for immortal time bias

PURPOSE

In cohort studies on liver cancer, there are often immortal time bias and interference of competing risk events. This study proposes to explore the role of internal and external radiotherapy for hepatocellular carcinoma using SEER data, using a competing risk model and controlling immortal time bias.

METHODS

Data of SEER from 2004 till 2015 was included. To analyze whether there was a difference in survival between HCC (hepatocellular carcinoma) patients receiving external radiation and internal radiation, we used a competing risk analysis after excluding immortal time bias, and created a nomogram to assess the risk of cancer-specific death (CSD) in hepatocellular carcinoma patients receiving radiotherapy.

RESULTS

Potential confounding factors adjusted, there was no significant difference in CSD between external and internal radiation therapy [HR and its 95% CI = 1.098 (0.874-1.380)]. The constructed nomogram performed better than the traditional AJCC model. The AUC and calibration curve results showed that this well-calibrated nomogram could be used to make clinical decisions regarding the prognosis and personalized treatment of hepatocellular carcinoma treated. There was no difference in the cumulative risk of death between patients with liver cancer treated with external radiation therapy and internal radiation therapy.

CONCLUSION

There is no difference in the cumulative risk of death between patients with liver cancer treated with external radiation therapy and internal radiation therapy. The nomogram predicts the results more accurately. These results can be used to guide the choice of treatment options for patients with HCC and to predict their survival prognosis.

Why Metformin Should Not Be Used as an Oxidative Phosphorylation Inhibitor in Cancer Patients

BACKGROUND

Preclinical studies have suggested that metformin exerts antitumor effects on various types of cancers. However, the results of human clinical trials have been inconsistent.

SUMMARY

Metformin is widely considered to be a prime example of a clinically relevant compound that inhibits oxidative phosphorylation (OXPHOS). However, the efficacy of metformin in inhibiting OXPHOS in cancer patients remains uncertain. The available evidence suggests that the plasma concentration of metformin remains within the micromolar range when administered at therapeutic doses. While millimolar concentrations are necessary to inhibit complex I activity in isolated mitochondria, there is no evidence supporting the idea that metformin accumulates within the mitochondria. Metformin exerts a modest effect on the adenosine diphosphate to adenosine triphosphate (ATP) ratio, resulting in AMP-activated protein kinase activation, which promotes ATP-generating catabolic pathways and restores cellular energy balance.

KEY MESSAGES

The value of metformin as an OXPHOS inhibitor for cancer treatment is debatable, and caution should be exercised while using metformin for this purpose.

Core concepts in pharmacoepidemiology: Key biases arising in pharmacoepidemiologic studies

Pharmacoepidemiology has an increasingly important role in informing and improving clinical practice, drug regulation, and health policy. Therefore, unrecognized biases in pharmacoepidemiologic studies can have major implications when study findings are translated to the real world. We propose a simple taxonomy for researchers to use as a starting point when thinking through some of the most pervasive biases in pharmacoepidemiology. We organize this discussion according to biases best assessed with respect to the study population (including confounding by indication, channeling bias, healthy user bias, and protopathic bias), the study design (including prevalent user bias and immortal time bias), and the data source (including misclassification bias and missing data/loss to follow up). This tutorial defines, provides a curated list of recommended references, and illustrates through relevant case examples these key biases to consider when planning, conducting, or evaluating pharmacoepidemiologic studies.

The Impact of Epithelial-Mesenchymal Transition and Metformin on Pancreatic Cancer Chemoresistance: A Pathway towards Individualized Therapy

Globally, pancreatic ductal adenocarcinoma remains among the most aggressive forms of neoplastic diseases, having a dismal prognostic outcome. Recent findings elucidated that epithelial-mesenchymal transition (EMT) can play an important role in pancreatic tumorigenic processes, as it contributes to the manifestation of malignant proliferative masses, which impede adequate drug delivery. An organized literature search with PubMed, Scopus, Microsoft Academic and the Cochrane library was performed for articles published in English from 2011 to 2021 to review and summarize the latest updates and knowledge on the current understanding of EMT and its implications for tumorigenesis and chemoresistance. Furthermore, in the present paper, we investigate the recent findings on metformin as a possible neoadjuvant chemotherapy agent, which affects EMT progression and potentially provides superior oncological outcomes for PDAC patients. Our main conclusions indicate that selectively suppressing EMT in pancreatic cancer cells has a promising therapeutic utility by selectively targeting the chemotherapy-resistant sub-population of cancer stem cells, inhibiting tumor growth via EMT pathways and thereby improving remission in PDAC patients. Moreover, given that TGF-β1-driven EMT generates the migration of tumor-initiating cells by directly linking the acquisition of abnormal cellular motility with the maintenance of tumor initiating potency, the chemoprevention of TGF-β1-induced EMT may have promising clinical applications in the therapeutic management of PDAC outcomes.

The Association of Metformin, Other Antidiabetic Medications, and Statins With the Prognosis of Colon Cancer in Patients With Type 2 Diabetes: A Retrospective Cohort Study

BACKGROUND

Use of metformin and statins have been associated with improved prognosis of colon cancer (CC) in patients with type 2 diabetes (T2D). We examined the survival from CC in relation to the use of metformin, other oral antidiabetic medications (ADM), insulin, and statins in T2D patients.

MATERIALS AND METHODS

A cohort (n = 2252) of persons with pre-existing T2D diagnosed with incident CC between 1998 and 2011 was identified from several Finnish registers. Cox models were fitted for cause-specific mortality rates to obtain adjusted estimates of the hazard ratios (HR) with 95% confidence intervals (CI) in relation to use of ADM and statins before the CC diagnosis. Cox models were also fitted for mortality in relation to post-diagnostic use of the medications treating these as time-dependent exposures, and starting follow-up 1 year after the CC diagnosis.

RESULTS

Pre- and post-diagnostic metformin use was weakly associated with the risk of CC-related death (HR .75; 95% CI .58-.99, and HR .78; 95% CI .54-1.14, respectively) compared to the use of other oral ADMs. Pre- and post-diagnostic statin use predicted a reduced risk of CC-related death (HR .83; 95% CI .71- .98, and HR .69; 95% CI .54-.89, respectively).

CONCLUSION

Additional evidence was found for use of statins being associated with an improved survival from CC in patients with pre-existing T2D, but for metformin use the evidence was weaker.

Metformin and survival of women with breast cancer: A meta-analysis of randomized controlled trials

WHAT IS KNOWN AND OBJECTIVE

Metformin has been suggested to confer anticancer efficacy. However, it remains uncertain whether additional use of metformin could improve survival of women with breast cancer. We performed a meta-analysis of randomized controlled trials (RCTs) to evaluate the influence of metformin on survival outcome in women with breast cancer.

METHODS

Relevant RCTs were obtained by search of PubMed, Embase and Cochrane's Library databases from inception to 15 May 2021. A random-effects model incorporating the potential publication bias was used to pool the results.

RESULTS AND DISCUSSION

Five phase II RCTs including 396 non-diabetic women with breast cancer were included in the meta-analysis. Pooled results showed that additional use of metformin was not associated with improved progression-free survival (PFS, hazard ratio [HR]: 1.00, 95% confidence interval [CI]: 0.70 to 1.43, p = 0.98; I²  = 32%) or overall survival (OS, HR: 1.00, 95% CI: 0.71 to 1.39, p = 0.98; I²  = 0%). Sensitivity analysis by excluding one study at a time showed consistent results (HR for PFS: 0.91 to 1.14, p all >0.05; HR for OS: 0.88 to 1.21, P all >0.05).

WHAT IS NEW AND CONCLUSION

Current evidence from phase II clinical trials does not support that additional use of metformin could improve the survival outcome in women with breast cancer.

Diabetes and pancreatic cancer: Exploring the two-way traffic

Pancreatic cancer (PC) is often associated with a poor prognosis. Long-standing diabetes mellitus is considered as an important risk factor for its development. This risk can be modified by the use of certain antidiabetic medications. On the other hand, new-onset diabetes can signal towards an underlying PC in the elderly population. Recently, several attempts have been made to develop an effective clinical tool for PC screening using a combination of history of new-onset diabetes and several other clinical and biochemical markers. On the contrary, diabetes affects the survival after treatment for PC. We describe this intimate and complex two-way relationship of diabetes and PC in this review by exploring the underlying pathogenesis.

Metformin: review of epidemiology and mechanisms of action in pancreatic cancer

Pancreatic ductal adenocarcinoma continues to be a lethal disease, for which efficient treatment options are very limited. Increasing efforts have been taken to understand how to prevent or intercept this disease at an early stage. There is convincing evidence from epidemiologic and preclinical studies that the antidiabetic drug metformin possesses beneficial effects in pancreatic cancer, including reducing the risk of developing the disease and improving survival in patients with early-stage disease. This review will summarize the current literature about the epidemiological data on metformin and pancreatic cancer as well as describe the preclinical evidence illustrating the anticancer effects of metformin in pancreatic cancer. Underlying mechanisms and targets of metformin will also be discussed. These include direct effects on transformed pancreatic epithelial cells and indirect, systemic effects on extra-pancreatic tissues.

Metformin use and lung cancer survival: a population-based study in Norway

BACKGROUND

We assessed associations between metformin use and survival in a nationwide Norwegian cohort of lung cancer (LC) patients.

METHODS

The study linked 22,324 LC patients from the Cancer Registry of Norway diagnosed 2005-2014 with the Norwegian Prescription Database. We estimated associations of pre- and post-diagnostic metformin use with overall survival (OS) and LC-specific survival (LCSS) using multivariable time-fixed and time-dependent Cox regression.

RESULTS

Pre-diagnostic metformin use was not associated with improved survival in all patients. Nevertheless, pre-diagnostic metformin use was associated with better LCSS in squamous cell carcinoma (SCC) patients (hazard ratio (HR) = 0.79; 95% confidence interval (CI) 0.62-0.99) and in patients with regional stage SCC (HR = 0.67; 95%CI 0.47-0.95). Post-diagnostic metformin use was associated with improved LCSS in all patients (HR = 0.83; 95%CI 0.73-0.95), in patients with SCC (HR = 0.75; 95%CI 0.57-0.98), regional stage LC (HR = 0.74; 95%CI 0.59-0.94), and regional stage SCC (HR = 0.57; 95%CI 0.38-0.86). OS showed similar results. Analyses of cumulative use showed a dose-response relationship in all patients, patients with adenocarcinoma and SCC, and with regional and metastatic LC.

CONCLUSIONS

Metformin use was associated with improved survival, especially LCSS in patients with regional stage SCC. Further prospective studies are required to clarify the role of metformin in LC treatment.

Diabetes and Pancreatic Cancer-A Dangerous Liaison Relying on Carbonyl Stress

Simple Summary

Diabetic people have an increased risk of developing several types of cancers, particularly pancreatic cancer. The higher availability of glucose and/or lipids that characterizes diabetes and obesity is responsible for the increased production of highly reactive carbonyl compounds, a condition referred to as “carbonyl stress”. Also known as glycotoxins and lipotoxins, these compounds react quickly and damage various molecules in cells forming final products termed AGEs (advanced glycation end-products). AGEs were shown to markedly accelerate tumor development in an experimental model of pancreatic cancer and AGE inhibition prevented the tumor-promoting effect of diabetes. In humans, carbonyl stress has been associated with the risk of pancreatic cancer and recognized as a possible contributor to other cancers, including breast and colorectal cancer. These findings suggest that carbonyl stress is involved in cancer development and growth and may be the mechanistic link between diabetes and pancreatic cancer, thus representing a potential drug target.

Abstract

Both type 2 (T2DM) and type 1 (T1DM) diabetes mellitus confer an increased risk of pancreatic cancer in humans. The magnitude and temporal trajectory of the risk conferred by the two forms of diabetes are similar, suggesting a common mechanism. Carbonyl stress is a hallmark of hyperglycemia and dyslipidemia, which accompanies T2DM, prediabetes, and obesity. Accumulating evidence demonstrates that diabetes promotes pancreatic ductal adenocarcinoma (PDAC) in experimental models of T2DM, a finding recently confirmed in a T1DM model. The carbonyl stress markers advanced glycation end-products (AGEs), the levels of which are increased in diabetes, were shown to markedly accelerate tumor development in a mouse model of Kras-driven PDAC. Consistently, inhibition of AGE formation by trapping their carbonyl precursors (i.e., reactive carbonyl species, RCS) prevented the PDAC-promoting effect of diabetes. Considering the growing attention on carbonyl stress in the onset and progression of several cancers, including breast, lung and colorectal cancer, this review discusses the mechanisms by which glucose and lipid imbalances induce a status of carbonyl stress, the oncogenic pathways activated by AGEs and their precursors RCS, and the potential use of carbonyl-scavenging agents and AGE inhibitors in PDAC prevention and treatment, particularly in high-risk diabetic individuals.

No Effect of Metformin on Ovarian Cancer Survival: A Systematic Review and Meta-Analysis of Cohort Studies

Background:

A number of observational studies examined the association between metformin therapy and ovarian cancer survival outcomes, but the results are inconsistent.

Objective:

The study aimed to investigate the effect of metformin on survival for ovarian cancer patients.

Methods:

PubMed, Embase and Web of Science databases were searched for relevant studies from the inception to June 11, 2019. The strength of the relationship was assessed using summary of hazard ratios (HRs) with corresponding 95% confidence intervals (CI). Statistical analyses were carried out using the random-effects model.

Results:

Totally, 6 retrospective cohort studies involving 2,638 ovarian cancer patients were included. Metformin was not associated with improved overall survival (HR=0.78, 95% CI 0.54-1.12, P=0.175, I2= 61.6%) and disease- free survival (HR=0.49, 95% CI 0.20-1.17, P=0.106, I2=82.1%) in ovarian cancer patients compared to nonmetformin users.

Conclusion:

The current study provides preliminary evidence that metformin may not be associated with a survival benefit for ovarian cancer patients. More studies with rigorous designs are needed.