Risk of breast cancer by individual insulin use: an international multicenter study

The systematic case-referent method

The systematic case-referent method is a special case-referent design originally developed for pharmacoepidemiologic research purposes. It consists in the systematic collection of series of incident cases of various disorders and the assembling of a general reference pool, from which "controls" are secondarily selected to be matched to specific cases. Both series are collected independently from each other and with no a priori hypothesis to be investigated. The reference pool can be either general or limited to a subpopulation, representative of the source population of the cases. Based on clinical recruitment of cases and referents, the design allows a very high specificity of diagnosis and documentation of clinical variables. All cases and referents are systematically documented on all treatments received before the incidence of the cases or before identification of referents. This documentation is done preferentially using objective sources assembled independently (linkage to claims data, medical records, pharmacy records, prescription records, hospital discharge letters). It can be completed with patients' interviews using standardised research tools, in particular for over-the-counter drug use and self-medication, and for the documentation of adherence to treatment and specific time-windows of exposure. Likewise, all cases and all referents are systematically documented on a series of risk factors, which are common to most epidemiological studies and are not hypothesis-dependent. Whenever the documentation of a confounding factor specific to the disease at hand is necessary, additional questionnaires can be applied to all or a sample of patients. The method has been successfully implemented for the pharmacoepidemiologic study of myocardial infarction, stroke, lupus, multiple sclerosis, rheumatoid arthritis, Guillain Barré syndrome, idiopathic thrombocytopenic purpura, type 1 diabetes mellitus, suicide attempts, breast cancer, and other disorders, for the analysis of the risk or preventing action of NSAIDs, statins, antiplatelet agents, anticoagulants, insulins, vaccines and other drugs.

Effects of insulin and analogues on carcinogen-induced mammary tumours in high-fat-fed rats

It is not fully clarified whether insulin glargine, an analogue with a high affinity for insulin-like growth factor-1 receptor (IGF-1R), increases the risk for cancers that abundantly express IGF-1R such as breast cancer or some types of breast cancer. To gain insight into this issue, female Sprague-Dawley rats fed a high-fat diet were given the carcinogen N-methyl-N-nitrosourea and randomly assigned to vehicle (control), NPH (unmodified human insulin), glargine or detemir (n = 30 per treatment). Insulins were given subcutaneously (15 U/kg/day) 5 days a week. Mammary tumours were counted twice weekly, and after 6 weeks of treatment, extracted for analysis. None of the insulin-treated groups had increased mammary tumour incidence at any time compared with control. At 6 weeks, tumour multiplicity was increased with NPH or glargine (P < 0.05) and tended to be increased with detemir (P = 0.2); however, there was no difference among insulins (number of tumours per rat: control = 0.8 ± 0.1, NPH = 1.8 ± 0.3, glargine = 1.5 ± 0.4, detemir = 1.4 ± 0.4; number of tumours per tumour-bearing rat: control = 1.3 ± 0.1, NPH = 2.2 ± 0.4, glargine = 2.7 ± 0.5, detemir = 2.3 ± 0.5). IGF-1R expression in tumours was lower than that in Michigan Cancer Foundation-7 (MCF-7) cells, a cell line that shows greater proliferation with glargine than unmodified insulin. In rats, glargine was rapidly metabolised to M1 that does not have greater affinity for IGF-1R. In conclusion, in this model of oestrogen-dependent breast cancer in insulin-resistant rats, insulin and insulin analogues increased tumour multiplicity with no difference between insulin types.

Long-Term Use of Long-Acting Insulin Analogs and Breast Cancer Incidence in Women With Type 2 Diabetes

Purpose

The association between long-acting insulin analogs and increased breast cancer risk is uncertain, particularly with the short follow-up in previous studies. We assessed this risk long term in women with type 2 diabetes.

Methods

A population-based cohort of women 40 years or older, all of whom were treated with long-acting (glargine, detemir) or neutral protamine Hagedorn (NPH) insulin between 2002 and 2012, was formed using the United Kingdom’s Clinical Practice Research Datalink. Women were followed until February 2015 or breast cancer diagnosis. Cox proportional hazards models were used to estimate adjusted hazard ratios (HRs) and 95% CIs of incident breast cancer, comparing long-acting insulin analogs with NPH overall, as well as by duration and cumulative dose.

Results

The cohort included 22,395 women who received insulin treatment, with 321 incident breast cancer events occurring during up to 12 years of follow-up (incidence rate 3.3 per 1,000 person-years). Compared with NPH insulin, insulin glargine was associated with an increased risk of breast cancer (HR, 1.44; 95% CI, 1.11 to 1.85), mainly increasing 5 years after glargine initiation (HR, 2.23; 95% CI, 1.32 to 3.77) and after > 30 prescriptions (HR, 2.29; 95% CI, 1.26 to 4.16). The risk was particularly elevated among prior insulin users (HR, 1.53; 95% CI, 1.10 to 2.12) but not for new users, which included fewer patients and for which one cannot rule out an HR of 1.81. The risk associated with insulin detemir was not significantly elevated (HR, 1.17; 95% CI, 0.77 to 1.77).

Conclusion

Long-term use of insulin glargine is associated with an increased risk of breast cancer in women with type 2 diabetes. The risk associated with insulin detemir remains uncertain because there are fewer users of this insulin.

Diabetes drugs and the incidence of solid cancers: a survey of the current evidence

INTRODUCTION

The evaluation of the relationship between the use of antidiabetic drug and the occurrence of cancer is extremely challenging, both from the clinical and pharmacoepidemiological standpoint. This narrative review described the current evidence supporting a relationship between the use of antidiabetic drugs and the incidence of solid cancers. Areas covered: Data from pharmacoepidemiological studies on cancer incidence were presented for the main antidiabetic drugs and drug classes, including human insulin and insulin analogues, metformin, sulfonylureas, glinides, alpha-glucosidase inhibitors, thiazolidinediones, incretin mimetics, and sodium glucose co-transporter 2 inhibitors. The relationship between the use of antidiabetics and the incidence of solid cancer was described in strata by any cancer and by organ-specific cancer and by drug and by drug classes. Information supporting biological evidence and putative mechanisms were also provided. Expert opinion: The history of exploration of the relationship between antidiabetic drugs and the risk of solid cancers has showed several issues. Unrecognized biases and misinterpretations of study results have had important consequences that delayed the identification of actual risk and benefits of the use of antidiabetic drugs associated with cancer occurrence or progression. The lesson learned from the past should address the future research in this area, since in the majority of cases findings are controversial and confirmatory studies are warranted.

Diabetes and Breast Cancer Subtypes

Background

Women with diabetes have a worse survival after breast cancer diagnosis compared to women without diabetes. This may be due to a different etiological profile, leading to the development of more aggressive breast cancer subtypes. Our aim was to investigate whether insulin and non-insulin treated women with diabetes develop specific clinicopathological breast cancer subtypes compared to women without diabetes.

Methods and Findings

This cross-sectional study included randomly selected patients with invasive breast cancer diagnosed in 2000–2010. Stratified by age at breast cancer diagnosis (≤50 and >50 years), women with diabetes were 2:1 frequency-matched on year of birth and age at breast cancer diagnosis (both in 10-year categories) to women without diabetes, to select ~300 patients with tumor tissue available. Tumor MicroArrays were stained by immunohistochemistry for estrogen and progesterone receptor (ER, PR), HER2, Ki67, CK5/6, CK14, and p63. A pathologist scored all stains and revised morphology and grade. Associations between diabetes/insulin treatment and clinicopathological subtypes were analyzed using multivariable logistic regression. Morphology and grade were not significantly different between women with diabetes (n = 211) and women without diabetes (n = 101), irrespective of menopausal status. Premenopausal women with diabetes tended to have more often PR-negative (OR = 2.44(95%CI:1.07–5.55)), HER2-negative (OR = 2.84(95%CI:1.11–7.22)), and basal-like (OR = 3.14(95%CI:1.03–9.60) tumors than the women without diabetes, with non-significantly increased frequencies of ER-negative (OR = 2.48(95%CI:0.95–6.45)) and triple negative (OR = 2.60(95%CI:0.88–7.67) tumors. After adjustment for age and BMI, the associations remained similar in size but less significant. We observed no evidence for associations of clinicopathological subtypes with diabetes in postmenopausal women, or with insulin treatment in general.

Conclusions

We found no compelling evidence that women with diabetes, treated with or without insulin, develop different breast cancer subtypes than women without diabetes. However, premenopausal women with diabetes tended to develop breast tumors that do not express hormonal receptors, which are typically associated with poor prognosis.

Antihypertensive agents and the risk of breast cancer in women aged 55 years and older: a nested case-control study

OBJECTIVE

The study aimed to investigate the association of long-term use of different antihypertensive agents with incident breast cancer.

METHODS

A total of 794 ,533 women aged at least 55 years were identified from Taiwan National Health Insurance claims database during 2001-2011. As of 31 December 2011, incident breast cancer patients were included as cases, and 1 : 4 age-matched controls were selected by risk-set sampling scheme. Logistic regression models were applied to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) of breast cancer incidence associated with different durations of use of angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, β-blockers, and dihydropyridine calcium channel blockers (DHP CCBs). Different restriction rules were applied to reveal the potential effects of confounding by indication.

RESULTS

Among the 9397 incident breast cancer patients and 37 ,588 controls, a significantly elevated risk was found for relatively short-term use of DHP CCBs (<6 years) but not in those observed for more than 6 years. There was no association between either angiotensin-converting enzyme inhibitors/angiotensin receptor blockers or β-blockers use and breast cancer. Although restricting our analyses to those with any prescription of antihypertensive medications in 2001 or those with diagnosis of hypertension, there was no longer a statistically significant association between any use of DHP CCBs and breast cancer (OR: 1.21, 95% CI: 0.88-1.67 for the former, and OR: 1.71, 95% CI: 0.99-2.95 for the latter).

CONCLUSION

The results demonstrated the potential effect of confounding by indication, and thus, did not suggest any association of the use of antihypertensive medication and breast cancer risk.

Effect of Long-Acting Insulin Analogs on the Risk of Cancer: A Systematic Review of Observational Studies

OBJECTIVE

Observational studies examining the association between long-acting insulin analogs and cancer incidence have produced inconsistent results. We conducted a systematic review of these studies, focusing on their methodological strengths and weaknesses.

RESEARCH DESIGN AND METHODS

We systematically searched MEDLINE and EMBASE from 2000 to 2014 to identify all observational studies evaluating the relationship between the long-acting insulin analogs and the risk of any and site-specific cancers (breast, colorectal, prostate). We included cohort and case-control studies published in English on insulin glargine and detemir and any cancer incidence among patients with type 1 or 2 diabetes. The methodological assessment involved the inclusion of prevalent users, inclusion of lag periods, time-related biases, and duration of follow-up between insulin initiation and cancer incidence.

RESULTS

A total of 16 cohort and 3 case-control studies met our inclusion criteria. All studies evaluated insulin glargine, and four studies also examined insulin detemir. Follow-up ranged from 0.9 to 7.0 years. Thirteen of 15 studies reported no association between insulin glargine and detemir and any cancer. Four of 13 studies reported an increased risk of breast cancer with insulin glargine. In the quality assessment, 7 studies included prevalent users, 11 did not consider a lag period, 6 had time-related biases, and 16 had short (<5 years) follow-up.

CONCLUSIONS

The observational studies examining the risk of cancer associated with long-acting insulin analogs have important methodological shortcomings that limit the conclusions that can be drawn. Thus, uncertainty remains, particularly for breast cancer risk.

Metabolic, anabolic, and mitogenic insulin responses: A tissue-specific perspective for insulin receptor activators

Insulin acts as the major regulator of the fasting-to-fed metabolic transition by altering substrate metabolism, promoting energy storage, and helping activate protein synthesis. In addition to its glucoregulatory and other metabolic properties, insulin can also act as a growth factor. The metabolic and mitogenic responses to insulin are regulated by divergent post-receptor signaling mechanisms downstream from the activated insulin receptor (IR). However, the anabolic and growth-promoting properties of insulin require tissue-specific inter-relationships between the two pathways, and the nature and scope of insulin-regulated processes vary greatly across tissues. Understanding the nuances of this interplay between metabolic and growth-regulating properties of insulin would have important implications for development of novel insulin and IR modulator therapies that stimulate insulin receptor activation in both pathway- and tissue-specific manners. This review will provide a unique perspective focusing on the roles of "metabolic" and "mitogenic" actions of insulin signaling in various tissues, and how these networks should be considered when evaluating selective pharmacologic approaches to prevent or treat metabolic disease.

Treatment with insulin (analogues) and breast cancer risk in diabetics; a systematic review and meta-analysis of in vitro, animal and human evidence

INTRODUCTION

Several studies have suggested that anti-diabetic insulin analogue treatment might increase cancer risk. The aim of this study was to review the postulated association between insulin and insulin analogue treatment and breast cancer development, and plausible mechanisms.

METHOD

A systematic literature search was performed on breast cell-line, animal and human studies using the key words 'insulin analogue' and 'breast neoplasia' in MEDLINE at PubMed, EMBASE, and ISI Web of Science databases. A quantitative and qualitative review was performed on the epidemiological data; due to a limited number of reported estimates, a meta-analysis was performed for glargine only. A comprehensive overview was composed for in vitro and animal studies. Protein and gene expression was analysed for the cell lines most frequently used in the included in vitro studies.

RESULTS

In total 16 in vitro, 5 animal, 2 in vivo human and 29 epidemiological papers were included. Insulin AspB10 showed mitogenic properties in vitro and in animal studies. Glargine was the only clinically available insulin analogue for which an increased proliferative potential was found in breast cancer cell lines. However, the pooled analysis of 13 epidemiological studies did not show evidence for an association between insulin glargine treatment and an increased breast cancer risk (HR 1.04; 95 % CI 0.91-1.17; p=0.49) versus no glargine in patients with diabetes mellitus. It has to be taken into account that the number of animal studies was limited, and epidemiological studies were underpowered and suffered from methodological limitations.

CONCLUSION

There is no compelling evidence that any clinically available insulin analogue (Aspart, Determir, Glargine, Glulisine or Lispro), nor human insulin increases breast cancer risk. Overall, the data suggests that insulin treatment is not involved in breast tumour initiation, but might induce breast tumour progression by up regulating mitogenic signalling pathways.

Investigational new insulin glargine 300 U/ml has the same metabolism as insulin glargine 100 U/ml

Insulin glargine is processed in vivo into soluble 21(A) -Gly-human insulin (M1), the principal moiety responsible for metabolic effects, and subsequently into M2. This sub-study compared metabolism and metabolite pharmacokinetic (PK) profiles of investigational new insulin glargine U300 (Gla-300) with insulin glargine 100 U/ml (Gla-100, Lantus®, Sanofi-Aventis Deutschland GmbH, Frankfurt am Main, Germany) in people with type 1 diabetes. Participants received 0.4 (n = 18) or 0.6 U/kg Gla-300 (n = 12), and 0.4 U/kg Gla-100 (n = 30) once daily in randomized order for 8 days prior to a 36-h euglycaemic clamp. Metabolites were quantified using immunoaffinity enrichment and liquid chromatography tandem mass spectrometry (LC-MS/MS). Glargine metabolism was the same regardless of Gla-100 or Gla-300 administration; M1 was confirmed as the principal active moiety circulating in blood. Steady state concentrations of M1 were achieved after 2 days for Gla-100, and 4 days for Gla-300. Steady state M1 values defined prolonged and even flatter PK profiles after Gla-300 administration compared with M1 profiles after Gla-100.

Insulin and IGFs in obesity-related breast cancer

Obesity and the Metabolic Syndrome are associated with multiple factors that may cause an increased risk for cancer and cancer-related mortality. Factors involved include hyperinsulinemia, hyperglycemia, hyperlipidemia and IGFs. Insulin resistance is also associated with alterations in the levels of proinflammatory cytokines, chemokines, adipokines (leptin, adiponectin) that may also be contributing factors. The insulin family of proteins is ubiquitously expressed and has pleiotropic effects on metabolism and growth. However insulin, IGF-1 and particularly IGF-2 have been identified as tumor promoters in multiple studies. Mouse models have focused on insulin and IGF-1 and their receptors as being involved in tumor progression and metastases. The role of the insulin receptor as either mediating the effects on tumors or as compensating for the insulin-like growth factor receptor has arisen. Its role has been supported by preclinical studies and the importance of insulin resistance and hyperinsulinemia in obesity and early diabetes. Since the focus of this review is the insulin-family we will focus on insulin, IGF-1 and IGF-2.