Testicular cancer incidence trends in the USA (1975-2004): plateau or shifting racial paradigm?

OBJECTIVE: It has been reported that the incidence of testicular cancer has plateaued in some parts of the USA, especially among non-Hispanic Whites in Los Angeles. Temporal trends analysis was conducted over three decades to assess the evidence for such a plateau, and to examine whether the incidence of testicular cancer remains stable across racial/ethnic groups. This study also investigated the influence of age at diagnosis on the incidence of testicular cancer.

STUDY DESIGN: Population-based temporal trends analysis.

METHODS: Using the Surveillance Epidemiology and End Results (SEER), 16,580 newly diagnosed cases of testicular cancer in males aged 15-49 years were identified between 1975 and 2004. Incidence rates were examined by calculating the age-adjusted rates and their 95% confidence interval (CI) for age at diagnosis, SEER areas and race for the year of diagnosis. The percentage change and annual percentage change were examined for trends.

RESULTS: The incidence of testicular cancer is continuing to increase among US males, despite the plateau of the 1990s. Between 1975 and 2004, the age-adjusted incidence rate for males aged 15-49 years increased from 2.9 (1975) to 5.1 (2004) per 100,000. The trends indicated a percentage change of 71.9% and a statistically significant annual percentage change of 1.6% (95%CI 1.3-2.0; P<0.05). Although the incidence of testicular cancer in Blacks remained strikingly low (0.3-1.4 per 100,000), the highest annual percentage change was observed among this group (2.3%, 95%CI 0.8-3.9; P<0.05 for trends). The rates were intermediate among Asians/Pacific Islanders and American Indian and Alaska Natives (0.7-2.9 per 100,000), with a percentage change of 117.3% and a statistically significant annual percentage change of 1.5% (95%CI 0.3-2.7; P<0.05 for trends). The highest rates were reported among Whites (3.2-6.3 per 100,000), with a percentage change of 90.4% and a statistically significant annual percentage change of 2.0% (95%CI 1.6-2.3; P<0.05). The most common age at diagnosis was 30-34 years, while the lowest rates were reported in those aged 15-19 years. Likewise, incidence rates varied by SEER areas, with predominantly White states representing areas associated with the highest reported rates of testicular cancer.

CONCLUSIONS: Overall, the incidence of testicular cancer continues to plateau in the USA, while racial variance persists. Black males demonstrate the greatest increase in annual percentage change. Further studies are needed to examine the recent increase among Black males and the potential determinants.