Introduction:
Type 2 diabetes is associated with an increased risk of some types of cancer. Diabetes treatment may also modify cancer risk.

Objective:
The aim of this retrospective, case-control study was to assess whether HbA_1c level and use of anti-diabetic drugs are associated with cancer development in a diabetic population.

Material and Methods:
The case group consisted of 53 patients who developed cancer after diagnosis of diabetes. They were compared with 53 diabetic subjects without cancer, strictly matched to a case group by age and gender. In both groups – apart from HbA1c and diabetes treatment – demographic data, smoking habits, comorbidities, BMI, diabetes duration, use of aspirin, antihypertensive and hypolipemic drugs were also analyzed.

Results:
Patients with cancer had a significantly higher mean HbA_1c value compared with the control group, 7.83±1.26% vs. 7.30±1.08%, respectively (p=0.022). The distribution of patients in four HbA_1c categories (<7.0, 7.0-7.9, 8.0-8.9 and ≥9.0%) was significantly different between the two groups (p=0.031). The probability of cancer was higher among patients with HbA_1c value ≥8.0 % OR 3.160 (95% CI 1.342-7.440), p=0.013, and lower among patients using metformin, OR 0.228 (95% CI 0.083-0.633), p=0.006. The number of insulin users, insulin dose, duration of insulin treatment, and use of other anti-diabetic drugs were not significantly different between the two groups. Also, no significant differences were found between the two groups regarding other variables.

Conclusions:
The presented case-control study indicated an important role of metabolic control and confirmed the protective role of metformin in reducing cancer risk among patients with type 2 diabetes. Contrary to other studies, insulin use was not associated with a higher risk of cancer. Other anti-diabetic drugs appeared to have a neutral impact on cancer development.