The Relationship between Type 2 Diabetes and Cancer: An integrative review

(	Mutaz Arafat Moh`d. Altamimi Correspondence: Email: mutaztamimi@yahoo.com

Abstract Background: There is evidence to suggest that type 2 diabetes may increase the risk of incidence of cancer. Type 2 diabetes is characterized by insulin resistance and hyperinsulinemia. Hyperinsulinemia may lead to cancer through insulin's effect on its cognate receptor and the insulin-like growth factor system. Methods: An integrative review of the literature focused on 9 articles 2009-2013, and was completed to determine the Relationship between Type 2 Diabetes and Cancer. Conclusions: Substantial evidence suggests that people with type 2 diabetes have an increased risk of developing several types of cancers. Key words: diabetes mellitus, cancer, diabetes type 2, epidemiology, incidence, relationship, diagnosis, risk factor

Introduction
Diabetes mellitus (DM) is a serious growing health problem worldwide and is
associated with severe acute and chronic complications that negatively influence both the
quality of life and survival of affected individuals (Vigneri P, Frasca F,Sciacca L, Pandini
G, vigneri R, 2011). Globally, as of 2010, an estimated 285 million people had diabetes
with type 2 making up about 90% of the cases. Its incidence is increasing rapidly and by
2030, this number is estimated to almost double (Wild S, Roglic G, Green A, Sicree R,
King H, 2004). Therefore, if diabetes is associated with a small increase in the risk of
cancer, this may have important consequence at the population level (Vigneri et al.,
2011). So Diabetes and cancer are common diseases that have a tremendous impact
on health worldwide. The epidemiological evidence suggests that people with diabetes
are at a significantly higher risk of many forms of cancer as type 2 diabetes and cancer
shares many risk factors (Giovannucci et al., 2010). However, the links between diabetes
and cancer are still not well understood. Moreover, evidence from observational studies
suggests that some medications used to treat hyperglycemia are associated with either an
increased or reduced risk of cancer (Giovannucci et al., 2010). Moreover, some but not
all epidemiologic studies have suggested that diabetes significantly increases mortality in
patients with cancer (Chustecka, 2010).

In this review, we will assess the available evidence about the association between type 2
diabetes mellitus and cancer, the different aspect of diabetes type 2 which may influence
this association and the possible mechanisms involved.

Methodological Characteristics
The 9 studies composing this integrative research review were quantitative studies. Four studies were review studies, two studies were meta analysis studies, two studies were cohort studies and one was a case control study. Although only 9 studies were included in this research review, a wide variety of instruments were used to measure concepts related to the relationship between Type 2 Diabetes and Cancer. Most instruments were used in these studies to collect information to measure the effect of type 2 diabetes mellitus on development of cancer by review, review and analysis or comparing populations. The samples in articles are composed of males and females with type 2 diabetes mellitus and the age of samples varied. Many types of cancer were included in this review such as colorectal cancer, prostate cancer, and primary liver cancer.

Design
An integrative review method was used which encompasses a diverse form of research
studies, including experiment and non-experimental ones to understand the phenomenon
of interest (Whittemore & Knafl, 2005). Integrative review may also combine data from
theoretical as well as empirical literature. In addition, integrative review incorporates a
wide range of purposes: to define concepts, to review theories, to review evidence, and to
analyse methodological issues of a particular topic (Broome, 1993). Cooper (1998)
delineates five stages of research review: problem identification, data collection, data
evaluation, analysis and interpretation, and presentation of findings.

Search strategy
A literature search was conducted through the major electronic database
MEDLINE. Articles reviewed were limited to primary research reports and
published in English from 2009 to 2013. One hundred and forty one articles were
identified through the database search and review of reference lists, of which some
articles were duplicated. Also some articles were excluded because they were not related to
diabetes and cancer or they were not empirical studies but were discussions, opinions or
editorial articles. Eventually, only 9 articles were included in this review.

Keywords used in literature search were: diabetes mellitus, cancer, diabetes type 2,
epidemiology, incidence, relationship, diagnosis, risk factor

Data extraction and synthesis
Each of the 9 studies was analysed and categorized according to the types of
methodology used. The following characteristics were recorded: purpose of the study,
study design, population and outcomes of the findings.

Sample Characteristics
The sample in the 9 studies in this review contains people who with diabetes type 2
and diagnosed with cancer or risk for cancer. The sample contains male and female from
different age. Cancer sites in sample were mainly liver, prostate, esophageal, and
colorectal.

Results
The studies have shown a link between type 2 diabetes and cancer. Positive correlation
between type 2 diabetes and cancers of the colon, breast, liver, and pancreas. In other
hand the type 2 diabetes is significantly inversely associated with risk of developing
prostate cancer, and this may be due to lower testosterone levels in men with type 2
diabetes.

Conclusion
Substantial evidence suggests that people with type 2 diabetes have an increased risk
of developing several types of cancers. These associations may be due to a number of
direct and indirect mechanisms. Recommendations to do more researches to decrease the
risk of cancer for patients Suffer from diabetes and to increase the awareness among
patients to do screening from time to time that reduce the risk of cancer.

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