Diabetes and cancer I: risk, survival, and implications for screening

Abstract

Type 2 diabetes mellitus (DM) and cancer are common diseases that are frequently diagnosed in the same individual. An association between the two conditions has long been postulated. Here, we review the epidemiological evidence for increased risk of cancer, decreased cancer survival, and decreased rates of cancer screening in diabetic patients. The risk for several cancers, including cancers of the pancreas, liver, colorectum, breast, urinary tract, and endometrium, is increased in patients with DM. In a pooled risk analysis weighting published meta-analytic relative risk (RR) for individual cancer by differences in their incidence rates, we found a population RR of 0.97 (95 % CI, 0.75-1.25) in men and 1.29 (95 % CI, 1.16-1.44) in women. All meta-analyses showed an increased relative risk for cancer in diabetic men, except studies of prostate cancer, in which a protective effect was observed. The relationship between diabetes and cancer appears to be complex, and at present, a clear temporal relationship between the two conditions cannot be defined. DM also impacts negatively on cancer-related survival outcomes and cancer screening rates. The overwhelming evidence for lower cancer screening rates, increased incidence of certain cancers, and poorer prognosis after cancer diagnosis in diabetic patients dictates a need for improved cancer care in diabetic individuals through improved screening measures, development of risk assessment tools, and consideration of cancer prevention strategies in diabetic patients. Part two of this review focuses on the biological and pharmacological mechanisms that may account for the association between DM and cancer.

Fig. 1

Pooled risk analysis of cancer in diabetic males. Pooled risk of cancer in the population with diabetes using population weights and quality weights in diabetic males. Studies are arranged in increasing order of the effect size (indicated by box size), and population weights are based on US cancer incidence of the specific cancer. The solid line at 1 indicates a relative risk (RR) of 1.0, and the solid line through the diamond represents the overall RR, with the diamond representing the 95 % CI

Fig. 2

Pooled risk analysis of cancer in diabetic females. Pooled risk of cancer in the population with diabetes using population weights and quality weights in diabetic females. Studies are arranged in increasing order of the effect size (indicated by box size), and population weights are based on US cancer incidence of the specific cancer. The solid line at 1 indicates a relative risk (RR) of 1.0, and the solid line through the diamond represents the overall RR, with the diamond representing the 95 % CI