25-hydroxyvitamin D and breast cancer, colorectal cancer, and colorectal adenomas: case-control versus nested case-control studies

Abstract

Background: Existing literature includes concerns regarding reliability of case-control studies of breast cancer incidence with respect to 25-hydroxyvitamin D (25(OH)D) concentrations. For breast cancer, only case-control studies consistently find inverse correlations between 25(OH)D and breast cancer. However, for colorectal cancer, nested case-control studies find significant inverse correlations with respect to 25(OH)D concentrations at baseline for mean follow-up times of 7 years.

Materials and methods: This is a review of results currently existing in literature.

Results: I provide evidence that 25(OH)D concentration values are only useful for short follow-up times for breast cancer since it develops rapidly. To support the robust nature of breast cancer case-control studies, I show that results from 11 studies from seven countries align in a robust power-law fit to the odds ratio versus mean 25(OH)D concentrations.

Conclusion: Case-control studies of breast cancer incidence rates provide reliable results.

Keywords: Breast cancer; case-control study; colorectal adenoma; colorectal cancer; nested case-control study; vitamin D.