Background: A few recent studies suggest that the ratio of the lengths of the second to the fourth finger (2D:4D) may relate to cancer development, including prostate cancer. Low 2D:4D has been linked to higher intrauterine testosterone exposure, possibly explaining such findings.
Aim: To assess the association between 2D:4D and prostate cancer risk.
Methods: This analysis was carried out in the context of PROtEuS: Prostate Cancer & Environment Study, a population-based case-control study conducted in Montréal, Canada. Subjects included 1,937 incident prostate cancer cases aged ≤ 75 years, histologically-confirmed, diagnosed across French hospitals in Greater Montreal in 2005-2009. Concurrently, 1,995 population controls from the same residential area were randomly selected from the French electoral list, and frequency-matched to cases by age (±5 years). In-person interviews elicited information on socio-demographic, lifestyle and environmental factors. The lengths of the 2nd (index) and 4th finger (ring) of the right hand of study subjects were measured by trained interviewers. Unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CI) for the association between 2D:4D and prostate cancer risk, adjusting for age, ancestry, and a first-degree family history of prostate cancer.
Results: The OR for each increment of 2D:4D, defined a one standard deviation, was 0.917 (95% CI: 0.857-0.981). Corresponding ORs were 0.931 (95% CI: 0.866-1.002) and 0.882 (95% CI: 0.796-0.976) for men diagnosed with less and more aggressive cancers, respectively. ORs stratified by age at diagnosis/interview (˂ 60, ≥ 60 years) did not differ. In analyses restricted to men of African descent, the OR for each increment of 2D:4D was 1.284 (95% CI: 0.989-1.665).
Conclusions: Our findings suggest an inverse association between 2D:4D and prostate cancer risk, particularly pronounced for aggressive cancers. Contrastingly, there was evidence of a positive association among men of African descent.