Hidaka A, et al. - Researchers assessed how cancer risk is affected by insulin and blood glucose individually. For this purpose, they determined the links between plasma C-peptide, a surrogated marker of insulin, and glycated albumin (GA), a more stable marker of blood glucose, with all-site and site-specific cancer risk by mutually accounting for their confounding effects. Findings suggested the possible relevance of higher insulin levels, independently of higher blood glucose levels, in DM-related carcinogenesis for several cancer sites. In the assessment of cancer risk, even in individuals who have not developed DM, the examination of circulating insulin levels was suggested to be a plausible option.

Methods

• In this prospectively conducted study, nearly 4,000 cancer cases who answered the baseline questionnaire and supplied blood samples were recruited from a population-based cohort of 33,736 subjects.
• Researchers analyzed 3,036 cancer cases and 3,667 sub-cohort subjects after exclusion of subjects with apparent DM.

Results

• After adjustment for GA levels, a statistically significant association of highest levels of C-peptide with an increased risk of all-site (hazard ratio [HR]: 1.21; 95% confidence interval: 1.02-1.42), colon (1.73; 1.20-2.47), liver (3.23; 1.76-5.91), kidney, renal pelvis, and ureter cancers (2.47; 1.07-5.69), vs the respective lowest levels, was observed among men and women combined.
• Among these C-peptide-related cancers, independently of C-peptide levels, an increased risk related to elevated GA levels was demonstrated by colon and liver cancers.
• According to findings, the corresponding HRs for colon and liver cancers vs the highest and lowest GA levels were 1.43 (1.02-2.00) and 2.02 (1.15-3.55), respectively.
• Only the link between C-peptide and colon cancer was effect modified by gender (P for interaction= 0.04).