digit ratio (2d:4d) is associated with breast cancer

Purpose: Digit ratio (2D:4D) has been considered as a proxy biomarker for prenatal hormonal exposure and may represent an individual’s predisposition to breast cancer. The purpose of the present study is to investigate whether there is a link between digit ratio and breast cancer in a Brazilian population.

Methods: Digital measurements of the lengths of the index and ring fingers of both hands were obtained from women with breast cancer (n = 100) and age-matched controls (n = 100) using a digital Vernier calliper. Mean digit ratios of right hands, left hands, and right minus left hand 2D:4D (DR-L) were compared between both groups. Data were analysed by the Student's t-test for unpaired samples, Mann-Whitney test, and Spearman`s correlation with a significance level of 5%.

Results: The patients with breast cancer presented significantly higher right and left 2D:4D (both p < 0.001) and higher DR-L (p = 0.032) than controls. Among breast cancer cases, there was a significantly negative correlation between left 2D:4D and age diagnosed with breast cancer (p = 0.018).

Conclusion: Digit ratio offers a valid retrospective biomarker of action of prenatal hormones and might be associated with breast cancer risk and age at onset of breast cancer. It suggests that higher exposure or sensitivity to prenatal oestrogen might be associated with a higher risk of breast cancer and with earlier onset of the disease.