International patterns suggest germ cell testicular cancer (GCTC) incidence may be lower in lower latitudes. To investigate this possibility, we examined GCTC incidence by latitude (population-centroid in 2000) for men >15 years within two reasonably homogeneous countries, the United States (US) and Australia. In the US, we examined age-adjusted incidence/latitude trends using data from states (2001-2010) and local-area registries (1980-2011). In Australia, we evaluated incidence/latitude trends in 61 Statistical Divisions (2000-2009). In White US men (68,566 cases), state incidences increased by latitude, rising 5.74% (4.45-7.05%) per 5°North latitude increment. Similar trends were found for seminoma and non-seminoma subtypes (p<0.001). In Black US men (2,256 cases), the association was also seen (4.9%; 0.2 to 9.7%). In local US data, similar increases in incidence with latitude were present in each of the last three decades. In Australia (6,042 cases), the incidence increased by 4.43% (95% CI: 1.54-7.39%) per 5°South, and trends for subtypes were similar. Thus, we found that incidence of GCTC in both White and Black men increased significantly with distance from the equator, approximately 1% per degree within the range of latitudes studied. This article is protected by copyright. All rights reserved.
Photochemistry and photobiology. 2016 Jul 11 [Epub ahead of print]
Robert J Biggar, Peter D Baade, Jiandong Sun, Lindsay E Brandon, Michael Kimlin
AusSun Research Laboratory, Institute of Health and Biotechnical Innovation, Queensland University of Technology, Brisbane, Australia., School of Public Health and Social Work, Queensland University of Technology, Brisbane, Australia., AusSun Research Laboratory, Institute of Health and Biotechnical Innovation, Queensland University of Technology, Brisbane, Australia., AusSun Research Laboratory, Institute of Health and Biotechnical Innovation, Queensland University of Technology, Brisbane, Australia., Cancer Council Queensland, Brisbane, Australia.