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Diabetes therapy and cancer risk: Where do we stand when treating patients?

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References

OTHER DIABETES THERAPIES

Alpha glucosidase inhibitors

Oral glucosidase inhibitors ameliorate hyperglycemia by inhibiting alpha glucosidase enzymes in the brush border of the small intestines, preventing conversion of polysaccharides to monosaccharides.64 This slows digestion of carbohydrates and glucose release into the bloodstream and blunts the postprandial hyperglycemic excursion.

The two alpha glucosidase inhibitors currently available in the United States are acarbose and miglitol, and although data are limited, they do not appear to increase the risk of cancer.65,66

Sodium-glucose-linked cotransporter 2 inhibitors

The newest class of oral diabetes agents to be approved are the sodium-glucose-linked cotransporter 2 (SGLT2) inhibitors canagliflozin (Invokana) and dapagliflozin (Farxiga).

SGLT2 is a protein in the S1 segment of the proximal renal tubules responsible for over 90% of renal glucose reabsorption. SGLT2 inhibitors lower serum glucose levels by promoting glycosuria and have also been shown to have favorable effects on blood pressure and weight.67,68

Canagliflozin was the first of its class to gain FDA approval in the United States. It has not been found to be associated with increased cancer risk.68

Dapagliflozin, originally approved in Europe, was approved in the United States on January 8, 2014. Because of a possible increased incidence of breast and bladder malignancies, the FDA advisory committee initially recommended against approval and required further data. In those who were treated, nine cases of bladder cancer and nine cases of breast cancer were reported, compared with one case of bladder cancer and no cases of breast cancer in the control group; however, the difference was not statistically significant.68

Since SGLT2 inhibitors are still new, data on long-term outcomes are lacking. Early clinical data do not show a significant increase in cancer risk.

WHAT THIS MEANS IN PRACTICE

Many studies have found associations between diabetes, obesity, hyperinsulinemia, and cancer risk. In the last decade, concerns implicating antihyperglycemic agents in cancer development have arisen but have not been well substantiated. At this time, there are no definitive prospective data indicating that the currently available type 2 diabetes therapies increase the incidence of cancer beyond the inherent increased risk in this population. What, then, is one to do?

Educate. Lifestyle modification, including weight management, should continue to be emphasized in diabetes education, as no therapy is completely effective without adjunct modifications in diet and physical activity. Epidemiologic studies have shown the benefits of lifestyle modifications, which ameliorate many of the adverse metabolic conditions that coexist in type 2 diabetes and cancer.

Screen for cancer. Given the associations between diabetes and malignancy, cancer screening is especially important in this high-risk population.

Customize therapy to individual patients. Those with a personal history of bladder cancer should avoid pioglitazone, and those who have had pancreatic cancer should avoid sitagliptin until definitive clinical data become available.

Moreover, patients with a personal or family history of medullary thyroid cancer should not receive GLP-1 receptor agonists. These agents should also probably be avoided in patients with a personal history of differentiated thyroid carcinoma or a history of familial nonmedullary thyroid carcinoma. Until we have further elucidating data, it is not possible to say whether a family history of any of the other types of cancer should represent a contraindication to the use of any of these agents.

Discuss. The multitude of diabetes therapies warrants physician-patient discussions that carefully weigh the risks and benefits of additional agents to optimize glycemic control and metabolic factors in individual patients.

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