To the Editor In the Korean national cohort study by Hwangbo and colleagues,1 cancer development was associated with an increased risk of diabetes. The authors interpreted this finding as the result of corticosteroid use, treatment with chemotherapy agents, or cancer cachexia. After 10-year follow-up, the authors observed that the risk of incident diabetes was significantly increased and reached a peak 1 to 2 years after cancer development, and then the risk declined to marginal significance or nonsignificance thereafter (as shown in Figure 2 of the article).1 Given this approximately J-shaped association, one may speculate that the early, temporarily high incidence of diabetes represents a compensatory biological adaptation, an adverse effect related to the toxic effects of cancer treatment, or cancer cachexia. Caution, however, must be taken in interpreting the pathogenetic role of cancer in the development of diabetes. Cancer and diabetes are closely associated with each other epidemiologically and biologically, and they share many risk factors, including aging, obesity, smoking, unhealthy diet, and physical inactivity.2 Currently, it remains unknown whether the high incidence of diabetes after cancer is associated with shared risk factors or if cancer independently contributes to the increased risk of diabetes.