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Sex Differences in Cancer Incidence in Type 2 Diabetes

Mar 24, 2018
 

Men and women with type 2 have different risk for obesity-related cancer when compared with general population.

Research shows that patients with type 2 diabetes (T2DM) have higher risk of developing liver, pancreas, endometrium, colon, rectum, breast and bladder cancer compared to general population. These types of cancer are very similar to obesity-related cancers. Since many T2DM patients have excessive weight or obesity, the risk factor for the development of cancer overlap. The goal of this prospective cohort study was to investigate the incidence of obesity-related cancers in women and men in relationship to the time of diabetes diagnosis. The obesity-related cancer risk was analyzed in three time frames: first year following diabetes diagnosis, 2 to 5 years after diagnosis of diabetes and in the period 5 years before the diagnosis of diabetes.

This study included cancer events that occurred between 1989 and 2012 and there was no age restriction for participation. Patients were excluded from the study if they had a short life expectancy, a cognitive impairment or were treated in secondary care. All T2DM treated in primary care practices were eligible to participate. A total of  69,583 participants were enrolled and 10,717 participants were diagnosed with 12,617 cancer events between the studied time. Only the first cancer event was included in the analysis of the results. 49% of the participants were female. Overall, women were older and had a higher BMI when compared with men. Other baseline characteristics such as diabetes duration, HbA1c, and creatinine at diabetes diagnosis were similar between the male and female groups.

The results of this study showed that out of the three time frames, participants had highest cancer incidence in the first year after diagnosis of diabetes. In women, in the 5 years prior to diabetes diagnosis, there was a significantly increased obesity-related cancer compared to women in general population. In women, the adjusted standardized incidence ratios (SIR) was highest in the first year after diabetes diagnosis and remained increased in the 5 years after diabetes diagnosis. Breast cancer showed that the SIR was increased for all time points except for the year before diabetes diagnosis where it decreased.

In men, there was no significant increased cancer risk in the 5 years to 1 year prior to diabetes diagnosis. However, in the year before and the year after diabetes diagnosis, the SIR showed significantly increased cancer risk compared to men in the general population. Analysis of prostate cancer showed that there was a decrease in overall incidence of prostate cancer in the 5 years prior to diabetes diagnosis compared to the general population. There was no significant difference observed in prostate cancer rates between the general population and in the years after diabetes diagnosis.

Overall, the SIR for obesity-related cancer was higher in women when compared to men for all years except the one year before diagnosis of diabetes. In women, increased cancer incidence started to increase from 5 years before diabetes diagnosis. In men, cancer incidence started to increase from only a year before diabetes diagnosis and 5 years after diagnosis.

In women, the increase in obesity-related cancer incidence with T2DM is largely due to the contribution of sex-specific cancers like breast cancer. Irrespective of the presence of obesity or not, women had higher breast cancer incidence after diabetes diagnosis than the general population. Previous studies show that breast cancer risk increases in the prediabetes phase. This may be because women put on more weight in the prediabetes phase. Breast cancer has a strong correlation with an increase in weight and that can explain the increased incidence of breast cancer in females with diabetes. Another reason that can contribute to the increased incidence of breast cancer in females with T2DM is that studies have shown that women with obesity have lower socioeconomic status and are less likely to attend breast screenings. It is also found that women with diabetes are less likely to perform a mammogram than women without diabetes. In men, studies show there might be a protective effect of T2DM to prostate cancer. Some studies already showed that there is a decreased risk of prostate cancer in T2DM patients. Furthermore, there is also evidence that prostate cancer might not be related to obesity.

Practice Pearls:

  • Women with type 2 diabetes have higher risk of obesity-related cancer than men.
  • Women’s risk of getting cancer increases years before diagnosis of diabetes and it usually starts in prediabetic phase.
  • In men, cancer incidence started to increase from only a year before diabetes diagnosis.

Reference:

Schrijnders D, Hendriks SH, Kleefstra N, et al. Sex differences in obesity related cancer incidence in relation to type 2 diabetes diagnosis. PLoS ONE 13(1): e0190870.