Early life risk factors for testicular cancer: a case-cohort study based on the Copenhagen School Health Records Register

Abstract

Purpose: One established risk factors for testicular cancer is cryptorchidism. However, it remains unclear whether cryptorchidism is a risk factor in itself or whether the two conditions share common causes in early life (estrogen hypothesis), such as birth weight and birth order. The objective of this study is to utilize data from the Copenhagen School Health Records Register (CSHRR) to evaluate cryptorchidism, birth weight and birth order as risk factors for testicular cancer.

Methods: The study population consisted of 408 cases of testicular cancer identified by a government issued identification number linkage of the entire CSHRR with the Danish Cancer Registry and a random subsample of 4819 males from the CSHRR. The study design was case-cohort and the period of follow-up between 2 April 1968 and 31 December 2003.

Results: Cryptorchidism was significantly associated with testicular cancer in crude analyses [hazard ratio (HR) = 3.60, 95% CI 2.79–4.65]. Birth weight was inversely associated with testicular cancer and no clear association with birth order was observed. The positive association between cryptorchidism and testicular cancer was only slightly attenuated controlling for birth weight and birth order and stratified on birth cohort (HR = 3.46, 95% CI 2.67–4.48).

Conclusion: This study confirmed the robustness of the association between cryptorchidism and testicular cancer even after adjustment for birth weight and birth order. Furthermore, the study showed an inverse association between birth weight and testicular cancer.

Acknowledgments

The application of data from the Copenhagen School Health Records Register for the present study was approved by the Danish Data Protection Agency. We are appreciative of the efforts required to build the Copenhagen School Health Records Register, which has been established in collaboration between the Institute of Preventive Medicine and the Copenhagen City Archives. We thank Dr Michael Gamborg for his help with the preparation of the Copenhagen School Health Records Register data for these analyses as well as Niels Erik Skakkebæk for helpful assistance and expertise in relation to the coding of genital abnormalities in the raw data.

Disclosure statement

The authors report no conflicts of interest.

Funding

This study was funded and conducted in collaboration with the unit of Survivorship, Danish Cancer Society Research Center.